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WaterH said:
Yes
Click to expand...
Ok

WaterH said:
And I just confirmed the contacts are bad. If I ground the trigger, the first fan relay “snaps” and a few seconds later the second one snaps.
Click to expand...

Sooo, that's where I'm not following you ?
You blew the trinary switch or the relay ?
If you ground the trigger (pin 86) and the fans turn on, that means the relays are still working ?!?
 
Bebop said:
Ok



Sooo, that's where I'm not following you ?
You blew the trinary switch or the relay ?
If you ground the trigger (pin 86) and the fans turn on, that means the relays are still working ?!?
Click to expand...
I had hell with the trinary switches from VA on my dads '66.
Its possible the 75a relay coil is wiping out the trinary switch from flyback.
ALL the relays should have flyback diodes on them.

Like this on the diagram.
71N7rVc0gxL._SL1500_.jpg
 
Again, stay simple and answer my questions.
If you apply ground to the pin 86, without changing anything else, do your fans turn on?

If yes, that means the relays are good.
 
WaterH said:
Yes

And I just confirmed the contacts are bad. If I ground the trigger, the first fan relay “snaps” and a few seconds later the second one snaps.

I don’t have the fan part number handy, but it is a high output Spal 12” fan. (it has brushes)

pic not very useful

9F80264B-3671-4A63-8F63-59D316F67387.jpeg
Click to expand...
Looking at this picture, what wire gauge are you using for the fan supply ?
They look awfully small.
 
The relays you used appear to have bleed resistors on the coil so you are probably ok there.
 
Bebop said:
Ok



Sooo, that's where I'm not following you ?
You blew the trinary switch or the relay ?
If you ground the trigger (pin 86) and the fans turn on, that means the relays are still working ?!?
Click to expand...

if I ground the trigger, the relay snaps, but the fan does not come on. If I jump across the relay, the fan comes on.

Bebop said:
Looking at this picture, what wire gauge are you using for the fan supply ?
They look awfully small.
Click to expand...

I believe the power is 10 GA, but the trigger wires are smaller.


I just wired a 100 amp relay in on the rear fan. I started the truck and turned on the AC. After a bit, the fan came on. I turned the AC switch off and the fan quit as fast as I could go around to check. Of course, it’s not real hot right now, so the pressure would not be up as much as summer.
 
WaterH said:
if I ground the trigger, the relay snaps, but the fan does not come on. If I jump across the relay, the fan comes on.



I believe the power is 10 GA, but the trigger wires are smaller.


I just wired a 100 amp relay in on the rear fan. I started the truck and turned on the AC. After a bit, the fan came on. I turned the AC switch off and the fan quit as fast as I could go around to check. Of course, it’s not real hot right now, so the pressure would not be up as much as summer.
Click to expand...
So the relays are failing the high current circuit not the coils.
Pop one open and see whats up?
 
I'm trying to understand things here...

WTF is going on ? :laughing:

Can you give us a diagram please ???

9F80264B-3671-4A63-8F63-59D316F67387.jpeg
 
Bebop said:
I'm trying to understand things here...

WTF is going on ? :laughing:

Can you give us a diagram please ???

9F80264B-3671-4A63-8F63-59D316F67387.jpeg
Click to expand...

So the delay timer is the box at the far left. No big current goes though it. The big current comes from the harness to the bolt on the right of the right relay. The green wire is goes to the + trigger spade. You can’t see it here, but the - trigger wire from the trinary goes to the same terminal as the blue wire. (when that wire gets ground the first relay clicks and starts the delay timer for the second relay. The black wire is the power for the timer. The purple wire sends ground to the second relay after a few seconds.

CarterKraft said:
So the relays are failing the high current circuit not the coils.
Pop one open and see whats up?
Click to expand...

B6A3F797-5ED7-4F80-AAC8-96DBABF94094.jpeg


The contacts do look a little hot.

1C3457F3-5C73-4E4C-9A2D-D86DF10980BF.jpeg


Bebop said:
Both fans are on one 10 AWG wire ?
That's very small for 44 amp constant draw.
Click to expand...

The main power wire from the bus bar is 6GA. (both fans) The wire from one relay to the second is 10GA. (Just one fan)
 
It's not a permanent solution, but you can probably clean the contacts and make it work again.

Is it possible that it's sitting on the trigger threshold and being activated rapidly and repeatedly?
 
If you have a shitty connection on the trigger wire it will rapid cycle and arc the shit out of the contacts. It's like it's trying to turn on and off a couple thousand times a minute. Will cook to contacts. As it is, those fans should not be an issue for those relays.
 
CarterKraft said:
Is it killing one or both relays?
Click to expand...

Both are dead. I installed one 100 amp relay temporarily. (I have another on order) The AC works great with one fan right now because it’s not really hot.

bdkw1 said:
If you have a shitty connection on the trigger wire it will rapid cycle and arc the shit out of the contacts. It's like it's trying to turn on and off a couple thousand times a minute. Will cook to contacts. As it is, those fans should not be an issue for those relays.
Click to expand...

I don’t think my connection is bad, but I can’t say about the trinary switch. Also, that trinary switch ground triggers both relays and the timer. Not sure if that could be too much. (Doesn’t seem like it would)

One thing I’m thinking about is just cut the trinary switch out of the fan circuit. I could make the AC switch trigger the fans. When the compressor turns off, so what if the fans keep running. Not going to hurt anything.
 
bdkw1 said:
If you have a shitty connection on the trigger wire it will rapid cycle and arc the shit out of the contacts. It's like it's trying to turn on and off a couple thousand times a minute. Will cook to contacts. As it is, those fans should not be an issue for those relays.
Click to expand...

That's the only explanation I see.

WaterH said:
One thing I’m thinking about is just cut the trinary switch out of the fan circuit. I could make the AC switch trigger the fans. When the compressor turns off, so what if the fans keep running. Not going to hurt anything.
Click to expand...
Was gonna be my suggestion. ditch the delay relay while you're at it.
Make sure to turn the AC off before turning the engine off.
 
Bebop said:
That's the only explanation I see.


Was gonna be my suggestion. ditch the delay relay while you're at it.
Make sure to turn the AC off before turning the engine off.
Click to expand...

The delay reduces the “inrush” of power at start up. Why ditch that? If the second relay was the only one to fail, I would think again. I have always turned off the AC prior to the engine.
 
bdkw1 said:
If you have a shitty connection on the trigger wire it will rapid cycle and arc the shit out of the contacts. It's like it's trying to turn on and off a couple thousand times a minute. Will cook to contacts. As it is, those fans should not be an issue for those relays.
Click to expand...
This x100. When I was a HVAC tech and a furnace had a weak/failing or bad wiring to the 24v circuit for the compressor the contactor would look just like this. The black is the clue. The surface of the contact point gets hot from the constant opening and closing. Can you run some test leads to the relays and watch the voltage? Maybe you are getting a voltage drop in the line somewhere and the relay is opening and then trying to close right back up. I don't understand the wiring exactly but could the secondary relay could drop the voltage enough to kill the first one and then they just play round and round we go?
 
Was doing it before the delay relay was added.

I'm saying the tinary switch isn't helping.
 
MattS said:
This x100. When I was a HVAC tech and a furnace had a weak/failing or bad wiring to the 24v circuit for the compressor the contactor would look just like this. The black is the clue. The surface of the contact point gets hot from the constant opening and closing. Can you run some test leads to the relays and watch the voltage? Maybe you are getting a voltage drop in the line somewhere and the relay is opening and then trying to close right back up. I don't understand the wiring exactly but could the secondary relay could drop the voltage enough to kill the first one and then they just play round and round we go?
Click to expand...
Bebop said:
Was doing it before the delay relay was added.

I'm saying the tinary switch isn't helping.
Click to expand...

You guys have me convinced to bypass the trinary switch. (For the fans) I have to say, I have never seen a trinary switch on any other car. Everything I have worked on the fans come on when you turn the AC on. There’s a pressure switch for the compressor, but not the fans.

As far as the delay timer, I think that’s good for the alternator. It doesn’t have to “ramp up” so fast when the fans come on. That’s another reason to get the fans off a pressure switch. The alternator probably doesn’t like going up and down every minute. It does allready for the compressor clutch, but that doesn’t draw near as much as the fans.
 
WaterH said:
You guys have me convinced to bypass the trinary switch. (For the fans) I have to say, I have never seen a trinary switch on any other car. Everything I have worked on the fans come on when you turn the AC on. There’s a pressure switch for the compressor, but not the fans.

As far as the delay timer, I think that’s good for the alternator. It doesn’t have to “ramp up” so fast when the fans come on. That’s another reason to get the fans off a pressure switch. The alternator probably doesn’t like going up and down every minute. It does allready for the compressor clutch, but that doesn’t draw near as much as the fans.
Click to expand...
I'm no electrician but I have had some huge stereo's in vehicles that would pull WAY more juice than some fans. Like stereo wire the size of your thumb thick. Never had any issues with the alternator. I think the battery helps to level the load. Once I got to a certain size I had huge capacitors in the system and they really didn't do anything until it was all the way up.
 
this sparked a question from a post on another thread. if you want constant duty can you use one of these

dam it is posted up above all ready. ahhaahah

1677258897730.png
 
When you have a hammer, everything is a nail.

You could also turn the AC on with a mecanical switch

51Ej3Xa64-S.jpg


No more problems. :flipoff2:
 
I think you just trigger the fan relays with a wire from the AC control panel when AC is called for.
Like was said, don't use the pressure/compressor status to trigger the fan relay. At minimum that is going to lessen the cycle count on those relays by thousands of cycles per week of operation.
 
CarterKraft said:
I think you just trigger the fan relays with a wire from the AC control panel when AC is called for.
Like was said, don't use the pressure/compressor status to trigger the fan relay. At minimum that is going to lessen the cycle count on those relays by thousands of cycles per week of operation.
Click to expand...

I thought I would put a copy of this here.

I thought I would update the question I had earlier on the relays. I got some that are the same part number as HYDRODYNANMIC. At first glance they look identical.

F2111038-6EE4-4BBA-9C37-5D781EB2DE9E.jpeg


Upon closer inspection, I noticed a couple differences. The main terminals on the Bosch are riveted through the plastic housing as apposed to the tab going right into the housing on the Tyco. Also, the output terminal on the Tyco relay has a copper tab on top of it.

3D500F75-F517-4437-9866-4D8FC1B91B3A.jpeg


Searching on the net suggests that polarity is not that important on many relays, but in this case, that copper tab on just one side indicates to me the polarity is important. (At least on this relay) The fact that the Bosch relay is listed as a starter relay for a motorcycle and the Tyco relay does not list an application other then continues duty is a good sign that it is of better quality. It maybe that this style relay was built for the starting purpose and then later they made a few changes to accommodate continues duty.

These are now installed with the trinary switch bypassed.
 
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