Electrical Trinary switch to trigger electric fan

foxbodybill89

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Jan 19, 2020
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The fans are wired together through two different relays in parallel. Both fans are wired directly to one relay and wired to a separate relay through the factory resistor to give the low speed. The controller is a microprocessor that just sends ground signals to switch between the two relays to either send power directly to the fans or through the resistor to the fans based on temp data. There is a separate wire from the A/C compressor wire to a terminal on the controller box, the controller senses the compressor turn on and switches the high speed relay on.

In the trinary switch diagram that karthief gave, if you wire it up with a relay exactly the same way but substitute the controller trigger wire for the fan on the purple wire from pin 87 I think it will do what you want.
 
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KRUISR

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I have also wired manual toggles for each speed. What I did last summer was when I wanted to have A/C on I simply flipped the low speed fan on. I left it running as long as I had A/C mode selected. It worked great. As I said before I also have a signal from the A/C clutch that can cycle low speed as well, but found that annoying (the constant short bursts of on and off) and decided to just turn low on manually.

Unless you can change what fan mode gets engaged when A/C turns on within your controller, I would wire it directly (not through the controller) with the trinary switch wired grounding a new relay that fires the low speed fan directly (tap into the output wire from your controller for low speed fan). Either that or wire a toggle to manually trigger low when you want A/C.
 

Noobz347

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Question:

Goal 1 is to eliminate the surge you get when the fans kick on. What are the other desires you're looking to get with this? Is this switch supposed to provide some sort of additional safety for the compressor?
 

Mstng93SSP

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Nope. 100% to eliminate the fan from kicking on high every time the compressor cycles. Super annoying. RPM's dip.....then settle back...then dip.....then ....you get the picture. With the AC off the thing idles perfect. Even when the AC is on and cycles (without the fan hooked up) still idles perfect. It's the draw of the fan kicking on high that messes with the idle. Yes I have a 3G alternator.
 

Noobz347

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If it were me (this may have been covered already in other terms):

I would wire the high-speed side of the fan to come on and stay on continuously when the HVAC is set to either A/C or MAX A/C. You might also try either disabling or putting onto a manual switch, the high side of just one of the fans. Reducing that load to one fan at a time may smooth your idle issues.

As a last (slightly more involved solution) you can put a delay in-line with one of the fans so that they don't both kick on (or up) simultaneously:
Amazon productView: https://www.amazon.com/Time-Delay-Relay-seconds-SPDT/dp/B0744HSF8P/ref=sr_1_2?dchild=1&keywords=12+volt+time+delay+relay&qid=1615098295&sr=8-2

Also: You may want to chase down the component that is being robbed of current and causing the dip in your idle. Is it the ignition? Is it the fuel pump? See if you can determine this piece. If it's the fuel pump, that's fairly easy to solve without even touching the fans.
 

96pushrod

I think they're a little easier to get off
May 15, 2018
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Do you run aftermarket engine management? If so you can command the engine to idle up with the ac comes on. You ideally want the fan to cut on when the ac does.
 

Sparky714

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Probably not what you want to hear, but I'd ditch that fan controller and get a PWM controller. A DCC or something similar. I have Contour fans and the DCC controller. One of the best upgrades I've done. Fans soft start and ramp up and down as needed. No sudden electrical load like relay controllers. It has an AC connection so fans will go to 50% whenever compressor is running.
 
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KRUISR

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No sudden electrical load like relay controllers.
It seems that nobody with the aftermarket controllers uses the factory Contour low speed function. Let me enlighten those. There is no sudden electrical load or idle surge if you use the low speed function. If you look at the Factory Contour wiring diagram I posted above, from the factory the Contour uses low speed for A/C. Why complicate things and have your controller turn on high speed fans. It makes no sense (because of the electrical load surge) and is not needed.

Here is a bit of advice for all those who are looking to install Contour fans with aftermarket controller. If you are pulling your fans from the wreckers (from Contour/Mystique or Cougar) take the wiring that connects the two motors (and had a ground cable as well). This will include the thermo resistor for low speed.
If you buy the fans from rockauto or LMR, the resistor is already there (according to the pictures they post). You simply need to wire it up. Ask if you need help, it is really simple to replicate the factory wiring.

Connect the trigger output from your controller of choice to the low speed relay (yes have your controller trigger a 70A relay to start low). Connect your A/C output to the same relay. Wire a second 70A relay to a toggle switch in the cabin. If the low speed fans do not cool enough, you have the ability to turn on high manually. I will bet you that you will NEVER NEED to flip that switch. Using low speed you will not even notice when the fans kick on.

Keep it simple. Why re-invent the wheel. Contours, Mystiques, Cougars (and Mondeos in Europe) have been operating these fans for decades without issue. Why try to think you know better. One of the best parts of using relays to provide power to the fans is you can get away with a very simple and cheap controller if you trust the factory Contour system. Again, ask if you need some clarity.

OP - your controller is fine, a simple addition will get you what you want.
 

Sparky714

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Oct 16, 2015
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It seems that nobody with the aftermarket controllers uses the factory Contour low speed function. Let me enlighten those. There is no sudden electrical load or idle surge if you use the low speed function. If you look at the Factory Contour wiring diagram I posted above, from the factory the Contour uses low speed for A/C. Why complicate things and have your controller turn on high speed fans. It makes no sense (because of the electrical load surge) and is not needed.

Here is a bit of advice for all those who are looking to install Contour fans with aftermarket controller. If you are pulling your fans from the wreckers (from Contour/Mystique or Cougar) take the wiring that connects the two motors (and had a ground cable as well). This will include the thermo resistor for low speed.
If you buy the fans from rockauto or LMR, the resistor is already there (according to the pictures they post). You simply need to wire it up. Ask if you need help, it is really simple to replicate the factory wiring.

Connect the trigger output from your controller of choice to the low speed relay (yes have your controller trigger a 70A relay to start low). Connect your A/C output to the same relay. Wire a second 70A relay to a toggle switch in the cabin. If the low speed fans do not cool enough, you have the ability to turn on high manually. I will bet you that you will NEVER NEED to flip that switch. Using low speed you will not even notice when the fans kick on.

Keep it simple. Why re-invent the wheel. Contours, Mystiques, Cougars (and Mondeos in Europe) have been operating these fans for decades without issue. Why try to think you know better. One of the best parts of using relays to provide power to the fans is you can get away with a very simple and cheap controller if you trust the factory Contour system. Again, ask if you need some clarity.

OP - your controller is fine, a simple addition will get you what you want.
I wasn't trying to start a pissing match about which fan controller is better, just chiming in on my personal setup which I prefer over relays. Just giving him another option to the setup that isn't working for him...............
 

KRUISR

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No offense taken.

I use a fan switch in lower rad hose. Its all good. Many use other controllers. My only point is don't fear the relay system, actually use it with whatever temp sensor system you want. I agree with everyone who says starting on high speed is a big electrical load - it is. That is why I recommend using the factory provided low speed function, it does not have that sudden load on the system. It provides more than enough air movement to cool things down.

To be honest, it wasn't until I put lighted toggle switches on that I even knew the fans were running (when engine was on). I would routinely toggle them with the engine off, just to make sure each mode worked.
 
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