Cooling Fan Tech

[HYDRODYNAMIC]

Compiling all the cooling tech into one thread. Not limited to just fans.

Brushless:
Brushless fans are taking over the OEM and aftermarket and they are starting to show up on the newer ULTRA4 builds. The most common right now is the brushless Spal fans and they are easy to tell from the motor design. The ones shown below are the GEN 2 motors. The older Gen 1 motors and controllers are discontinued as they have a different electrical signal system and do not interchange with GEN 2. The motors also look different.
The brushless fans also have all the new tech in the shroud and blade design compared to the older brushed versions. Some of them might look backwards as they are going towards a recessed/flush drop in shroud/fan style versus the traditional surface mount that sits up high. The deeper shroud design allows better air flow through the core. The deeper blade designs are also because they are more powerful and pull more pressure and it also makes them a quieter as the rpms are lower so the frequency is lower and less annoying.
The brushless fans are always connected to power and a third and fourth signal wire is used to turn the fans on. No external relays or controllers, everything is inside the motor. The signal can can be a constant on full rpm or a PWM signal to variable the rpm. The Spal temp sensor is a smart sensor that outputs a PWM signal with a percentage based on the predetermined temp range by the part number. If you dont use a sensor, one signal wire is grounded (-) and one is powered (+) and it doesn't need anything else to run.
When the fans start up they wiggle to find home and then slowly ramp up to the signaled speed. If you physically block the fan blade the controller will fault out and reset and try to power up again until the obstruction is removed. The fan also has overload protection and overheat protection. For instance mud or water, stick, or a bent shroud dragging on the blade. It can derate its power output to stay cool if things get too hot but at those temps your engine should be on fire. The sensor has a ramp so it starts out low say 25% and ramps up if the sensor temps are not dropping, so it only uses what power it needs to cool. One sensor can power multiple fans so they can all power up together and not have to stagger start them or have one pull air through the shroud if the other one is off.
Lastly is the run life of 30,000 hours at which 95% will keep going and 5% might fail. The brushless motors dont have brushes to wear out and are more efficient so they will outlast most any other moving part on a buggy. The other big part to life is that they are IP68 and IP6K9K so they keep water and dust out of the motor and controller.

Noise:
Noise pertains to both brushed and brushless. The small diameter thin blade designs are the worse for noise as they need to turn faster to make the same airflow as the deep curve blades, so their frequency goes up.

Blade and Guard Design:
This pertains to both brushed and brushless. Thin blades can not pull the same CFM with high restriction radiator cores. Free air yes, but load them up and they can not move the air like a thick blade. The thin blade guard designs don't handle the bottoming out and G force as well as the heavier built thick blade shrouds which have more support. That is why you will see CBR and others build metal support straps for the thin fans. The new brushless housings are taking the share of the R&D so the strength and blade design are on a whole nother level.
One of Spals first brushless fans was based off of a brushed housing and blade design that had a brushless motor droped in. The setup as good as it was was not optimized and ranged between 24-33 % efficiency. When the same 300W brushless motor is dropped into an optimized blade and housing the efficiency raises to 32-40%. The performance under higher pressures also jumped. At 180Pa the old fan put out 1000CFM while the optimized blade put out 1357CFM.

Temp Sensor Location:
My understanding from talking with Spal is to put the sensor on the hot side loop which includes the driver front of head or passenger rear of head or water pump outlet or on the radiator before it does any cooling so you have a faster reacting system and so the reading temps are in a closer range. The factory ECM triggers the fans based off of what the heads read. I have the factory ECM sensor in the front driver head, Autometer sensor in the passenger rear head, and thinking of putting the Spal sensor in the hot 5/8 outlet heater port that is currently blocked. FYI, the 3/4" heater port is the low pressure side return which is connected to the surge tank.

Future:
So i got to thinking about the history of junk yard cooling as well as the evolution of junk yard parts in general. Example the go to junk yard front axle for years was a Ford high pinion king pin 60 and no your rusted pile its not worth a grand anymore just because you have the last dinosaur in existence. Now that has been replaced by the super duty high pinion ball joint 60, dirt cheap and everywhere and aftermarket supported. For fans it has been the Volvo or Ford two speed brushed fan. What is the next fan and controller assuming it will be a brushless version. The Camaro SS and Cadillac had a 850W Spal OEM brushless as well as a 600W in the C6 or C7 Corvettes. People have been using these for swaps but there are some problems. GM noticed they were selling more replacement fans than they had cars on the road, it was messing up warranty and supply numbers. At the time a person could use the aftermarket Spal Gen1 sensor to control the fan as a stand alone or they could program the GM ECM to drive it. For a number of classified reasons (enter conspiracy theory’s here) Spal comes out with Gen2 fans and sensors, much better for aftermarket as the fans can be ran stand alone with no sensors. Downside is they run the inverse program now so they do not operate with GM products unless reprogrammed. The OEM fan prices raised to a sustainable price to equal supply and demand. There are some companies making controllers for the GM fans but at some point you might as well just get the aftermarket system, no cutting up an OEM shroud, no special controllers, all plug and play. Another route is to use an aftermarket ECM that has inputs and outputs with pulse modulation for controlling fans and fuel pumps and newer tech items. So what happens in the future, well it gets worse. In a few years the brushless fans will be running on LIN instead of PWM and that technology is far more advanced and secure in terms of proprietary design so unless a well equipped company reverse engineers a controller/ sensor the average DIY mechanic is not going to be able to adapt them for aftermarket at which point you end spending your time more wisely to earn money doing what your good at and buying the part rather than loose time and lost wages trying to figure out how to save a buck. That will be the case for most high tech equipment in the future, dealer only service and or repairs.

​
Parts:
SBL-TS-165P: 140°F to 165°F 12VDC temperature sensor
SBL-TS-185P: 165°F to 185°F 12VDC temperature sensor
SBL-TS-195P: 175°F to 195°F 12VDC temperature sensor
SBL-TS-215P: 190°F to 215°F 12VDC temperature sensor
SBL-YAZ-PT10 Harness with a Yazaki connector on one end that plugs on to the fan's connector. One is required for each brushless fan.
SBL-TS-HARN Harness to attach the SBL-TS** temperature sensors to the SBL-YAZ-PT10 brushless fan connector. One can be used for multiple fans.
Spal 30107125 GEN2 300W 15.2" Flush Mount Curved Blade Brushless Puller Fan, MFG Number: VA91-ABL326P/N-65A 12V
Spal 30107102 GEN2 500W 14" Drop In Curved Blade Brushless Puller Fan, MFG Number: VA116-ABL505P-105A 12V
Spal 30107087 GEN2 300W 12" Drop In Saw Blade Brushless Puller Fan, MFG Number: VA89-ABL320P/N-94A 12V
Spal 30107089 GEN2 300W 10" Flush Mount Curved Blade Brushless Puller Fan, MFG Number: VA109-ABL321P/N-109A/S 12V

 

[HYDRODYNAMIC]

My Build:
The radiator is a 16" x 30" x 2.375" cross flow dual pass bar style with AN20 fittings. The trans cooler is a Thermal Transfer MA32 single pass which is around 15.75" x 16.34" x 2.625" core. The radiator uses dual 500W 14" VA116-ABL505P-105A rated at 1942 CFM each at 150Pa pressure. The trans cooler is a single 300W 15" VA91-ABL326-65A rated at 1357 CFM at 150Pa pressure. The CFM ratings shown are calculated for the style and size of the cores. Every fan will have a different CFM based upon shroud and core design.

The stock 6.0 water pump should flow 20GPM at 2000RPM and 66GPM at 6000RPM
The radiator should remove 196,000BTU/Hr. at 140ETD at 20GPM and 245,000 BTU/Hr. at 140ETD at 66GPM which is equivalent to 77-96HP. 140ETD means 220 degree fluid entering with 80 degree ambient air cooling the radiator.
Rule of thumb: About one third of the heat generated by the engine goes into the coolant/water mixture and must be dissipated by the radiator. That would mean the 96HP x 3 = 288HP, but radiators of this size are commonly rated at 600HP. So I am at a loss of the industrial ratings vs what is working. Still digging.

The pressure drop across the radiator should be around 15 PSI at 66GPM which is very close to the cap pressure so I am wondering what pressure the LS pumps flow at and how close it gets to the cap pressure. I might do some flow testing to see what actual flow and pressure are.

The 4L80 should flow 4-8GPM (best info I could find)
The MA32 should remove 50,000BTU/Hr. at 100ETD which is equivalent to 20HP

I plan to run the SBL-TS-165P on the trans cooler which will turn on at 140* and be full speed at 165*. For the radiator I plan to run a 180* thermostat or a restrictor with a SBL-TS-215P which will turn on at 190* and be full speed at 215*

Since the radiator is low and behind the seats there is no supplemental air flow from the vehicle moving so the fans are the only means of cooling. I wanted the cooling system sending the heat out the back and away from the engine and occupants as well as down low to provide better visibility and lower the CG and safer by not having the radiator facing any occupants.

 

[HYDRODYNAMIC]

Power Steering Cooling:
With 40"+ tires being the new common size and speeds going up the horsepower of the steering systems are going up as well. If you are working the system in the rocks or revving the pump at high speed, heat will be generated from the restriction of flowing oil. Systems that got away with only reservoir cooling or small passive heat sinks are going to need active cooling with radiator style construction.
The cooler I am going to use is a Thermal Transfer MA-4 with 8" or 10" Spal fan. The core is 8" x 8" x 2.5" and the overall is 10.5 x 9.7 x 2.6 with #16 SAE ports. The MA series is similar to the bar and fin style oil coolers sold by Griffin, CBR, and Triton which are commonly used for transmissions or engine oil coolers. The inside of the bars have passage ways "turbulators" to interact with the fluid and transfer more heat. The bar style is also a higher pressure rating at 300 PSI and can handle more impact from debris and vibration.
The MA-4 is rated at a 10psi pressure drop at 20GPM.
100ETD = 180* hot entering oil - 80* cooling ambient air.
It can remove 18,000 BTU/H @ 100 ETD or 7HP worth of heat if the hot oil is 180 and the outside air is 80.
It can remove 9,000 BTU/H @ 50 ETD or 3.5HP worth of heat if the hot oil is 130 and the outside air is 80.

 

[gt1guy]

Here's a couple pics of the new Spal brushless fans installed. There's not much that sticks out the back of the shroud. These are 12" ABL320P fans.

Radiator is a C&R 22"H x 27"W x 3"core. AN 20/24 fittings. Mounted, the radiator has a 33* rearward lean, that's why all the fittings are looking up at 33*, they are horizontal when mounted.

 

[BlackSheepRacing]

Nice to see information again!

 

[WaterH]

Very nice thread. Lots of good info. I'm going to throw my two cents in about fans. I'm not sure if it can be of any use in the 4x4 world.

Years ago, I was involved in redesign of a cooling fan on a helicopter. This fan was cooling a air cooled engine. Let me make clear, I'm not a fan engineer. So I consulted some fan experts. We ended up making a few changes I'll get to in a minute. But the most interesting thing I learned may or may not be of interest to you all. There are two kinds of fans.

Fans that make air pressure and fans that air velocity. All the fans that are the subject of this thread are of velocity style. The velocity style is not particularly good at pushing air through a radiator. Hence the reason most use them to vacuum air through the radiator. The most common "air pressure" style fan is the squirrel cage fan. Those fans are very efficient and are really good at pushing or pulling air and are far less likely to stall. They are generally quieter to boot. We were not able to incorporate a squirrel cage in our design, but they have been successfully used on some other helicopters. I'm courious why they arnt used on cars and trucks .

As far as the changes we did make, we "cupped" the blades and changed the inlet to the fan. It did improve the cooling, but basically we inherited a bad design and worked with what we had.

 

[scooter2374]

Just like the pbb mods can't change thread titles, Austin might be able.

 

[gt1guy]

Very nice thread. Lots of good info. I'm going to throw my two cents in about fans. I'm not sure if it can be of any use in the 4x4 world.

Years ago, I was involved in redesign of a cooling fan on a helicopter. This fan was cooling a air cooled engine. Let me make clear, I'm not a fan engineer. So I consulted some fan experts. We ended up making a few changes I'll get to in a minute. But the most interesting thing I learned may or may not be of interest to you all. There are two kinds of fans.

Fans that make air pressure and fans that air velocity. All the fans that are the subject of this thread are of velocity style. The velocity style is not particularly good at pushing air through a radiator. Hence the reason most use them to vacuum air through the radiator. The most common "air pressure" style fan is the squirrel cage fan. Those fans are very efficient and are really good at pushing or pulling air and are far less likely to stall. They are generally quieter to boot. We were not able to incorporate a squirrel cage in our design, but they have been successfully used on some other helicopters. I'm courious why they arnt used on cars and trucks .

As far as the changes we did make, we "cupped" the blades and changed the inlet to the fan. It did improve the cooling, but basically we inherited a bad design and worked with what we had.

Most squirrel cage fans are rather large. You'd most likely have to mount it somewhere else and run duct to the back of the radiator.

 

[StanF512]

Nice topic! Maybe it's just too early in the morning, but where are you buying the Spal brushless fans? I'm looking for a 16", va117-abl506p-103a, and it seems like Wizard Cooling is the only place that has it on their webpage.

 

[EndlessMtnFab]

Money aside ..... information like this really makes me wonder what kind of fan I want for the Jeep now.

I can get a nice 17 inch OE Benz mechanical fan and clutch for about $100 (good, used for OM606). Impressive as the brushless Spals are .... that single fan is capable of pulling more air into the engine bay. But, as already noted --- the fan is only a portion of the cooling equation.

I'm going with a mechanical injection pump for the diesel .... which will lower the electrical requirements to a small degree. Running a pair of 12s (40 amps each) will require an even bigger alternator than what i felt would be sufficient (accounting for winch, wipers, HVAC, etc). I already commented somewhere else on the site ... that a clutch fan would have a little bit more leeway for a water crossing compared to a fixed or flex fan --- but nothing like an on/off switch for an electric fan.

Even with the short nose I am going to use .... I have enough room to run the mechanical fan, however an extra inch or two would give me a little more room in the small engine bay (who knows what she said). The further back the motor sits, the better balanced the chassis will be. OTOH, forward makes for a slightly better driveshaft setup.

I don't know if there is enough "Freed HP" to make a difference between the 2 electrics vs 1 clutched mechanical. Same for theoretical fuel efficiency. Bigger alternators take a bit more energy to spin.

I'm kind of spaced out with meds at the moment ..... but are they are other pros & cons that I am missing at this moment in time? Yes --- I have deliberately ignored other cooling factors (airflow thru the bay, high temp coatings on exhaust, etc).


Thoughts, inputs, or comments on my ramblings?

 

[M92PV4U]

Money aside ..... information like this really makes me wonder what kind of fan I want for the Jeep now.

I can get a nice 17 inch OE Benz mechanical fan and clutch for about $100 (good, used for OM606). Impressive as the brushless Spals are .... that single fan is capable of pulling more air into the engine bay. But, as already noted --- the fan is only a portion of the cooling equation.

I'm going with a mechanical injection pump for the diesel .... which will lower the electrical requirements to a small degree. Running a pair of 12s (40 amps each) will require an even bigger alternator than what i felt would be sufficient (accounting for winch, wipers, HVAC, etc). I already commented somewhere else on the site ... that a clutch fan would have a little bit more leeway for a water crossing compared to a fixed or flex fan --- but nothing like an on/off switch for an electric fan.

Even with the short nose I am going to use .... I have enough room to run the mechanical fan, however an extra inch or two would give me a little more room in the small engine bay (who knows what she said). The further back the motor sits, the better balanced the chassis will be. OTOH, forward makes for a slightly better driveshaft setup.

I don't know if there is enough "Freed HP" to make a difference between the 2 electrics vs 1 clutched mechanical. Same for theoretical fuel efficiency. Bigger alternators take a bit more energy to spin.

I'm kind of spaced out with meds at the moment ..... but are they are other pros & cons that I am missing at this moment in time? Yes --- I have deliberately ignored other cooling factors (airflow thru the bay, high temp coatings on exhaust, etc).


Thoughts, inputs, or comments on my ramblings?

I have a k10 with a 454 im thinking about a electric fan and water pump so if/when the engine gets hot I can shut it off but circulate water and run the fan to cool the engine. But I'm probably over thinking it.

 

[arse_sidewards]

Money aside ..... information like this really makes me wonder what kind of fan I want for the Jeep now.

I can get a nice 17 inch OE Benz mechanical fan and clutch for about $100 (good, used for OM606). Impressive as the brushless Spals are .... that single fan is capable of pulling more air into the engine bay. But, as already noted --- the fan is only a portion of the cooling equation.

You're not gonna notice a loss of 5hp-10hp at peak in an off road application. If you have the room in front of the engine there's no good reason not to go with some sort of OEM style clutched mechanical fan.

Who the fuck cares if the radiators and other stuff matter too? You'd be stupid not to max out the fan portion of your cooling system when it costs you so little in terms of money and engineering tradeoffs.

 

[EndlessMtnFab]

Well .... tell that to all the people that are convinced their ebay triple fans are where it's at.

I honestly was looking to approach it from a different perspective, but not necessarily re-invent the wheel. Something as simple as better engine bay ventilation (hot air out) would probably do almost as much good as a 53,425 cfm fan of any kind. Especially with a turbo under the hood (in my case). Reducing exhaust heat is somewhat easy, but not really a cheap/cost-effective mod. Any gains there, in my opinion, would still fall under the "improving engine bay ventilation" category. Of course, that would still be indirectly assisting the cooling system.

Definitely wouldn't notice 5-10 offroad ..... but this Jeep will also be on the street. An extra 5-10 hp would be as useful on I-83 or I-81 as it would be on I-495 or I-290.

 

[Lil'John]

I prefer to go with an OEM electric fan if I'm forced to go that route. I figure the budget a car manufacturer has for fans is easily going to be 10x of Spal or the like. This should ensure best performance and longevity.

In my 2000 S10 with 4.3L, I am running a 99 Dodge Intrepid fans. Cools fine and replacements are going to be ~$70 for the whole thing. The stock plastic fan shroud of the Intrepid fits the stock radiator perfectly.

For the controller, I am using a Delta Current Control FK-95:
http://www.dccontrol.com/constant_te...ontrollers.htm

It turns the fans into variable speed so no load surge issues. It is compact(red box in picture). No special wiring needs: wire directly to fan, wire directly to battery. Push temp sensor into radiator fins.

It also provides LED feedback to show the speed the fan is running(green, yellowish, red)

Downside is price but the company has been around 20+ years and still is known for quality.

 

[HYDRODYNAMIC]

I prefer to go with an OEM electric fan if I'm forced to go that route. I figure the budget a car manufacturer has for fans is easily going to be 10x of Spal or the like. This should ensure best performance and longevity.

A lot has happened since the old open frame brushed motor you are using was designed. Spal is now a OEM supplier for GM and CAT and others. Some aftermarket companies can build a better and more cost effective product than the big automobile manufacturers. Example, all tires are from an aftermarket. Henry Ford tried to make his own rubber plantation and processing plant to make tires and it was a case story for what not to do. The guy who invented the assembly line and made cars affordable was better off letting others make some products for his cars rather than try to control everything.

 

[Lil'John]

A lot has happened since the old open frame brushed motor you are using was designed. Spal is now a OEM supplier for GM and CAT and others. Some aftermarket companies can build a better and more cost effective product than the big automobile manufacturers.<snip>

Supplier doesn't mean designer. There are many suppliers manufacture to someone else's specs. Whether that is the case with Spal supplied to oem, I couldn't tell nor do I care. I'll take a proven design for hundreds of thousands if not millions of cars each year over 'generic'.

And my favorite "qualifiers": some and can.

 

[Weasel]

oh like my OLD BMW that had fans that would randomly explode and cause you to instantly overheat? Good thing they have all that R&D money. Spal designs their own stuff. They are not just a "supplier".

I get your point, but it's not like that over the board.

 

[NEVERLIFT]

I read through pretty quick and may have missed it but heres another tip.

Do not mount the fan to the radiator with no shroud like this. I see this done a lot on drift cars and ls swap stuff.

I do not know how much more effective a tight fitting shroud is.
But in my simple brain; in the photo below you are using the whole radiator instead of just the area of the fan.

 

[arse_sidewards]

I read through pretty quick and may have missed it but heres another tip.

Do not mount the fan to the radiator with no shroud like this. I see this done a lot on drift cars and ls swap stuff.





I do not know how much more effective a tight fitting shroud is.
But in my simple brain; in the photo below you are using the whole radiator instead of just the area of the fan.

A lot of OEMs mount the fan like the top one and use a little circular shroud to make the fan efficiently pull or a big shroud with a bunch of flaps in it. The portion of the radiator without a fan behind it just gets whatever airflow it gets from the vehicle moving.

 

[NEVERLIFT]

...... The portion of the radiator without a fan behind it just gets whatever airflow it gets from the vehicle moving.

So in a crawling rig it would be better to have a full shroud? Then with something that sees any type of speed have somewhere for the air to move like flaps or leave some uncovered?

 

[EndlessMtnFab]

Personally .... I'd do the full shroud either way. If you have the time to come up with a fool-proof flap design --- by all means. I've seen/heard of a few flaps that ended up "sticking' in position over time.

I also feel that a funnel shape (of sorts) for the shroud will do even more to create even air flow than a boxed off shroud (by itself).

As for my own nonsense ..... I'm probably just going to do mechanical at this point. Just for the cost & simplicity of it. When I start making $85,000/year --- then I can experiment.

 

[crisbee1]

In a crawling rig screaming fans and loud fuel pumps suck balls.

 

[HYDRODYNAMIC]

For low speed use or crawling the fan is the main source of air flow since the vehicle speed is too low for forced air through the radiator. A deep shroud allows for the air to flow straight through the whole radiator and bend and change direction within the shroud area and be funneled to the round fan location and removed. If the shroud is very thin and close to the core, any forced air from moving at speed goes through the radiator and hits the shroud and gets backed up. The fan can not pull the air through the thin shroud section so it pulls through the open round section directly in front of it. Limiting the effective cooling area. So a deep shroud is best to provide plenty area for the air to bend and get to the fan. If you run a drop in flush mount brushless fan then the shroud will already be 2"-2.5" deep to house the fan. The flush mount fans also have a sloped profile so the outside edge of the blade is further from the core than the center motor location so it can pull in air easier. Anything mounted to the cooler needs a solid connection so nothing rubs or hits the core under vibration or it will wear away until it breaks or causes a leak. The flappers are ok on a high speed vehicle when the air flow will exceed the fan output or shroud flow rate. At some point if the shroud is too thin or fan not centered enough or no flappers you might as well run no shroud to allow the high speed forced air to flow freely.

 

[Weasel]

For low speed use or crawling the fan is the main source of air flow since the vehicle speed is too low for forced air through the radiator. A deep shroud allows for the air to flow straight through the whole radiator and bend and change direction within the shroud area and be funneled to the round fan location and removed. If the shroud is very thin and close to the core, any forced air from moving at speed goes through the radiator and hits the shroud and gets backed up.

That's were I messed up on mine, I don't think it's deep enough at 1/2".

 

[WaterH]

Old thread, but I figured I should ask this question here. I believe Hydrodynamic posted on another forum that shall remain nameless (pirate) about high quility relays and a trick timer device that would turn one fan on and turn the other a few seconds later. (To stop a inrush of current) I don't want to go back to that forum, so I'm hoping he or someone else has those particulars and could post them here.

 

[arse_sidewards]

Old thread, but I figured I should ask this question here. I believe Hydrodynamic posted on another forum that shall remain nameless (pirate) about high quility relays and a trick timer device that would turn one fan on and turn the other a few seconds later. (To stop a inrush of current) I don't want to go back to that forum, so I'm hoping he or someone else has those particulars and could post them here.

I don't see why you couldn't just use a diode and capacitor to make a relay that has a couple seconds delay and then wire it in parallel with a normal relay and power one fan off each

 

[Bebop]

You can also use a PWM controler like the C6 vette unit or the Ford Fusion ones as long as your ECU can be programmed to suit.

 

[HYDRODYNAMIC]

​

A two relay circuit with a switch to ground temp switch is a good redundant system, if one fan circuit goes down, you still have the other circuit. They will also start staggered so the starting amp draw on the electrical system only spikes half as much. This is what I did on my last setup, although I used the ECM to fire the relays. Using the sensors requires knowing at what temp you are measuring at what physical location in the system, as the temp in the engine can be different than what is read out at the radiator. It is possible that a radiator mounted 160 switch will begin to turn on when the hotter spots in the engine are at 180 or higher. A higher temp switch sensor might turn on too late when the engine is already too hot. So tune your temp sensor to best fit when you want them to turn on and just as importantly turn off or they will turn on and never turn off. The thermostat plays in this game as well or if you dont have a thermostat then the fans become the electronic thermostat.

You can also run one fan constant and have the other cycle with a sensor.

I would not run a variable speed controller with a brushed fan. If you want variable speed then you need to make the jump to Spal brushless fans with the built in controllers and matching temp sensors. Then you get the soft start, overload protection, built in relay, variable speed, high efficiency, and longer motor life in one package.

I ran these type of relays, alot of different vendors/brands sell them.
https://obtainsurplus.com/electrical...4m19storemulti

Time delay on relay solid state relay. Select the 0-10 or 0-60sec range. You might want more than 10 seconds so your batter/alt. can get the first fan up to speed and keep the total amps down before it gets hit again.
First fan relay circuit energizes timer and timed output triggers the second high amp relay. Don't use it for the full fan amps, which will be too high. Use the earlier linked 75A relay.

https://www.delcity.net/store/InPowe...20469.h_920471

 

[WaterH]

Those are the parts I was looking for. Thank you.

i am running two fans on my radiator like your first paragraph. I have it all wired, but I don't like spade connectors for the fan power. (They are fine for the relay triggers)

The reason for the delay is I have seperate fans for my AC condenser. I want both to come on almost the same time and I don't have anyway to do the staggered sensor thing on them. I'm running two giant battery's. So maybe the delay is not really needed.

 

[HYDRODYNAMIC]

Those are the parts I was looking for. Thank you.

i am running two fans on my radiator like your first paragraph. I have it all wired, but I don't like spade connectors for the fan power. (They are fine for the relay triggers)

The reason for the delay is I have seperate fans for my AC condenser. I want both to come on almost the same time and I don't have anyway to do the staggered sensor thing on them. I'm running two giant battery's. So maybe the delay is not really needed.

That's partly why I like those relays, they have secure screw terminals for the high power.
If your battery, wiring, and fuses are good for the load then it is a simpler system to turn everything on at the same time. Keep in mind I had a perfect storm one time where I had all the lights on, two fans on and I think the third fan and the air compressor turned on at the same exact time and it popped the main circuit breaker. It only happened one time, never again. Plan for everything to turn on at the same time with a spike load even though it might only happen 1% of the time. For instance my compressor runs at 45 amps continuous but restart spike can hit 230 amps for a second. Your fans might run at 30 amps continuous but they could spike 90 amps at startup.