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Switched power options

Eric

Eric

RIP 10/6/2022
Joined
May 22, 2020
Member Number
1141
Messages
1,414
Loc
Exeter, RI
Wiring gurus.

I'm in the process of wiring my buggy. PSI Conversions harness and computer for LS1. Painless Performance off-road chassis harness and switch panel.

I want the computer, cooling fans, and fuel pump run off key switched power. Turn the key and everything works. There are 4 fans total, dual Spal fans on the radiator and smaller Derale coolers for transmission and steering fluid. All the wiring diagrams I am looking at show switched power coming directly from the key switch. Hooking 5 or 6 power wires to the key switch does not give me the warm and fuzzies; especially since if everything is running at once there could be 60-80 amp draw.

What I am thinking is to install a bus bar fed by a relay that is controlled by the key switch. Everything running off switched power will be fed from the bus bar. Make sense? I'm not seeing any relays that can handle that much amperage. What other options exist?

Thanks!
 
why not a relay for each item? that way if one relay goes bad your other items still work....
 
Continuous duty solenoid is what you're after. Switched coil like a relay but rated for waaayyy more amps. I use them in front of blue sea fuse boxes for exactly what you're describing.
 
You dont want to switch the main power feed to the fans/pump/computer
use individual relays to handle all the current and the ign switch will send power to the relay coil
 
Last edited:
92 s dime said:
You dont want to switch the main power feed to the fans/pump/computer
use individual relays to handle all the current and the ign switch will send power to the relay coil
Click to expand...

This is another option that I had been considering. In fact it's how I had been planning to configure the system before the second guessing started.

Can you elaborate further on why this approach would be preferred over energizing a common bus bar from the key? Either way, each individual component will still be driven by its own relay.
 
Eric said:
This is another option that I had been considering. In fact it's how I had been planning to configure the system before the second guessing started.

Can you elaborate further on why this approach would be preferred over energizing a common bus bar from the key? Either way, each individual component will still be driven by its own relay.
Click to expand...

Are you thinking of running all or the load side of the relays from the bus bar or the coil wire off the bus bar?
 
Treefrog said:
Are you thinking of running all or the load side of the relays from the bus bar or the coil wire off the bus bar?
Click to expand...
Load. Fans are all triggered by computer (cooling) or thermostats (transmission and steering). The fuel pump and computer are of course triggered by the key switch.
 
Eric said:
Load. Fans are all triggered by computer (cooling) or thermostats (transmission and steering). The fuel pump and computer are of course triggered by the key switch.
Click to expand...

I don't see a reason not too use a high amperage relay to energize a common positive. Though I would tend to use a fuse block for the common positive over using just a bus bar.
 
Treefrog said:
I don't see a reason not too use a high amperage relay to energize a common positive. Though I would tend to use a fuse block for the common positive over using just a bus bar.
Click to expand...

The bus bar feeds a fuse block that includes all the relays
 
Muckin_Slusher said:
12voltguy

?
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that's who came to mind, I liked the setup james put in ruby (cleetus mcfarland youtube) I imagine it wasn't cheep don't remember the brand, but it was all basic controls On, start, turn signals, power windows, etc. Not sure it was dimmable That I would want.
 
On my old rig I ran a hot to an insulated post then ran keyed relays off of it. But that was under a gutted dash in a cab. I’ve been giving this a lot of thought for my buggy build. At some point you have to get a big current wire under there to feed your relays.
 
I think my setup is similar to Treefrog. I pulled one wire off a keyed source to charge the coil of a relay. I got a 12 spot fuse block, and that relay energizes that whole fuse block. My fans have separate direct power draw for the main supply. I connected my fan controller to this switched fuse block with a 5 amp fuse to keep the amps low in this block.
 
WMIF said:
I think my setup is similar to Treefrog. I pulled one wire off a keyed source to charge the coil of a relay. I got a 12 spot fuse block, and that relay energizes that whole fuse block. My fans have separate direct power draw for the main supply. I connected my fan controller to this switched fuse block with a 5 amp fuse to keep the amps low in this block.
Click to expand...
This is almost exactly what I did. I put some inline fuses on the switched side of the relay as well.
 
The plan is to use a continuous-duty solenoid that is energized via the key switch. Output from the solenoid provides switched power to the fans and fuel pump. All the fans and fuel pump have their own fuse and relay. The "control" side of the relays also use switched power. Fuel pump is always on with the key but the fan relays are ground activated by thermostats.
 
I kept burning up 30 amp plug in relays for my radiator fan so I went to this for all of my fans. Each port is 20 amp. I wired 2 in parallel for the radiator fan. I use one other for my trans cooler fan. Have not had a problem in 2 years.

Power from the relay comes from an ignition relay. Rad fan stays on all the time. Trans fan is on a thermostat.

www.summitracing.com

MSD Ignition 7564 MSD Solid State Relays | Summit Racing

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View attachment 377619
 
They make a high current version now which will handle a fan on each output.

I'd suggest that.

MSD 75643-HC High-Current Solid-State Relay 35Ax4, Black

Clean up your wiring with an MSD Solid-State High Current Relay Block. This high current module takes the place of 4 standard relays and eliminates unsightly wiring. Four independent channels can be activated using either power or ground. Each channel is capable of handling up to 35 Amps of...
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You can use the ECU and / or the Key On wire to trigger the outputs no problem.
 
Good to know. A club member had mentioned the msd unit but 20 amps is borderline for the radiator fans. I will check it out.
 
Eric said:
Yup, carpenter bee kit. There was a carpenter bee thread in gcc last week. Lol
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Haha....I just screenshot that to send to austin because I thought it was an ad showing up mid-thread. That was my bee thread last week and I assumed it was a targeted ad!

(FYI - there was bug in the migration and pics are getting swapped around between threads. They're working on it!)
 
Inpowerllc might have a continuous duty solid state relay thay will work for you. Like a 200 amp maybe. It is a board, you can set timers so after shutoff your fans can run a few minutes until the relay shuts off.
 
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