Cooling fan mod diagram

[Mantis_Toboggan]

EA82

So with all the buzz about cooling fan circuitry, I've realised that my prior mod was incorrect, seeing as the thermoswitch is actually a ground switch. I had originally thought it was on the "high side", or the "hot side". Now that I can safely say that such is not the case, I'm rebuilding my circuit again.

 

I call it "full on double relay all across the circuit".

I realise it's a bit of overkill, but I'm having fun with it.

 

Here it is!

Edited September 5, 2010 by Mantis_Toboggan

[GeneralDisorder]

Why the second 5 way relay?

 

I don't get the point of shunting the fan leads to ground with the 5-way's like that. The factory relay's are simple 4 pin relay's.

 

Are you thinking that you need to shunt the fan motor to ground so it doesn't create transients from wind rotation and damage itself? I don't think that's really an issue with these but I could see it on something larger....

 

The relay for the thermo-switch really isn't needed either - just move the indicator lamp over to the relay coil lead from the switch. Make it an LED and you don't need any extra fusing either. The relay coil's can run off the same fuse as the fan. You should only need a single fuse for this circuit. The coil's and the lamp draw insignificant amperage compared to the fan.

 

1 fuse, 1 relay is all this should take. You work for NASA or something?

 

GD

Edited September 5, 2010 by GeneralDisorder

[Mantis_Toboggan]

Why the second 5 way relay?

 

I don't get the point of shunting the fan leads to ground with the 5-way's like that. The factory relay's are simple 4 pin relay's.

 

Are you thinking that you need to shunt the fan motor to ground so it doesn't create transients from wind rotation and damage itself? I don't think that's really an issue with these but I could see it on something larger....

 

The relay for the thermo-switch really isn't needed either - just move the indicator lamp over to the relay coil lead from the switch. Make it an LED and you don't need any extra fusing either. The relay coil's can run off the same fuse as the fan. You should only need a single fuse for this circuit. The coil's and the lamp draw insignificant amperage compared to the fan.

 

1 fuse, 1 relay is all this should take. You work for NASA or something?

 

GD

 

NASA? Haha, not yet!

 

I want the wiring mod to be a switched addition to the factory setup.

First, I haven't noticed my fan turn on ever since I bought the damned battlewagon.

 

So I include a 4-way to turn on a light, indicating that the thermoswitch is functioning. Also, I can reference the temperature in which it turns on. I chose the relay instead of running in series because I was concerned about the added resistance, which would change the point in which the thermoswitch activated the fan. Plus I can ground the light inside the dash.

 

I used two 5-way relays because I wanted total circuit isolation, this way doesn't turn on the indicator light when I manually override the fan control. If the thermoswitch is broken or fails, the second 5-way allows a dedicated backup ground.

 

My override control takes it's power supply from a switched 12V source, so the fan doesn't stay on when I turn the car off. Also, the switch is itself lighted when closed.

 

The over-fusing is to protect the factory and indication circuits from voltage spikes that may occur due to my car being a bucket. I intend on using my override circuit when I go wheelin', you never know what happens way up in the mountains! So I fuse protected that one too.

[GeneralDisorder]

So I include a 4-way to turn on a light, indicating that the thermoswitch is functioning. Also, I can reference the temperature in which it turns on. I chose the relay instead of running in series because I was concerned about the added resistance, which would change the point in which the thermoswitch activated the fan.

 

You fail to understand how the thermoswitch works - it is mechanical and does not depend on voltage - it will switch based on temperature irregardless of even having any voltage present. Thus adding the light inline with the switch would not change the value at which it closes.

 

I used two 5-way relays because I wanted total circuit isolation, this way doesn't turn on the indicator light when I manually override the fan control. If the thermoswitch is broken or fails, the second 5-way allows a dedicated backup ground.

 

If I were doing it - I would have the light in series with the fan so that the light was on if the fan was running. If I didn't see the fan light periodically comming on or it didn't come on when I threw the switch - then I know something is amiss. But really it's a bit academic - you can hear the fan at any speed slow enough to need it and above that it shouldn't be on anyway. The temp guage is a better indicator of something going wrong with the cooling system.

 

My override control takes it's power supply from a switched 12V source, so the fan doesn't stay on when I turn the car off. Also, the switch is itself lighted when closed.

 

Sure - but I don't understand the need for an overide.... the only overide you need is to turn the fan OFF for river crossings, etc. Otherwise the whole point of the thermo-switch is so you don't have to bother with manual fan controls. If something goes wrong with the thermo switch then just jumper across it till you get home

 

The over-fusing is to protect the factory and indication circuits from voltage spikes that may occur due to my car being a bucket. I intend on using my override circuit when I go wheelin', you never know what happens way up in the mountains! So I fuse protected that one too.

 

If you are doing all this wireing yourself then you should be able to know it's good enough to not short out - soldering and heat shrinking, etc. Any crappy wireing on the car will not be protected by the new fuses. One fuse is all you need for a relay and a fan.

 

I just think you are making this WAY too complicated and in doing so you are going to cause problems down the line. You'll have a billion relays and fuses in your car for all your accesories with wireing design's like that and if something goes pop - you'll be tracing wireing for hours trying to figure out what went wrong. .

 

For a wheeler - keep it simple. You have a better chance of getting home.

 

GD

[Mantis_Toboggan]

Hello from Italy!!

 

You fail to understand how the thermoswitch works

So you're saying that the thermoswitch is a coiled thermal spring inside a housing that closes the circuit at a certain expansion?

 

If I were doing it - I would have the light in series with the fan so that the light was on if the fan was running. If I didn't see the fan light periodically coming on or it didn't come on when I threw the switch - then I know something is amiss.

This is the point of the light.

Which would follow if there is a spring instead of a thermal resistor.

I'm actually surprised that an auto manufacturer would use a coiled thermal spring for a temp switch. Even still, you never know what the aftermaket makes.

 

but I don't understand the need for an overide.... the only overide you need is to turn the fan OFF for river crossings, etc.

I like that idea, I hadn't considered that. But then again, what about the water pump driven fan? Either way, let's be realistic, take an old EA82 up a mountain in the middle of summer, there's a decent enough chance that it'll overheat during wheeling challenges. Such that I'm gonna want to put that fan on myself, and I don't feel like grabbing a jumper from my wiring box in the middle of the mess. Flipping a switch to an isolated circuit is just right.

 

If you are doing all this wiring yourself then you should be able to know it's good enough to not short out

This is an old car. The previous owner incorrectly wired the stereo, which subsequently was stolen and a lot of the wires were cut when that happened. Any circuit that fails gets a freshly rebuilt one and the important ones have 'just in case' backups. That's just how I am. That being said, I'd like my cooling circuit properly protected from power spikes that may happen.

 

I just think you are making this WAY too complicated and in doing so you are going to cause problems down the line.

 

Proper planning prevents piss poor performance.

By having properly built, protected circuits with indicators and redundant overrides, I will end up with an quick solution to faulty circuits in critical functions.

 

I'm not trying to say that my way of doing things is the only way to do it, if you want to do it another way, that's fine by me! That being said, if anybody wants to keep their engine from overheating and to have an indicator for their fan, this is the most reliable way to do it. It doesn't cost much, and it'll handle power surges, especially useful if you have winches and lights.