Electrical Trinary switch to trigger electric fan

[Mstng93SSP]

Hi. Does anyone have a write up, or a diagram, or better yet pictures of the installation of a trinary switch on a foxbody factory AC system where electric fans have been installed? I have a contour electric fan setup, and I am using the Dakota Digital fan controller and a 70 amp relay for each fan. The fans work great but the way they instruct you to wire up the AC/Fan on is by tapping the wire on the compressor. Every time the compressor gets power and cycles the fans come on at the same time on high. This causes an annoying electrical load with causes my idle to surge slightly...just enough to really irritate me. I have read about trinary switches being used which will turn the fan on based on system pressure. This seems like a better setup. Thanks for any insight you might have on this.

Car is a 1993 with a 306 running a stinger pimp system.

Chris

 

[General karthief]

If found this, only because I wanted to know what a trinary switch is, I'm still not sure but I think I know what/how it does whatever it does.

Trinary Switch Wiring Diagram

Trinary switches provide compressor protection against high side pressures that are too high or too low. internal schematic for each of these switches.

wiringall.com

It shows single and duel fans,
I have wired a on/off override for my fan and nothing caught fire.
I could do this

 

[Mstng93SSP]

Yeah, my general basic understanding is it will turn on the fan when a certain pressure is reached. I am hoping someone has done this to their fox so I can see where they installed it and how they wired it up.

 

[Mustang5L5]

Why not just tap the wiring in ahead of the ac pressure switch off the Hvac controls? Your losing the power at the ac compressor due to the cycling of the switch but if you tap in before the switch it will be constant 12v to the dcc controller when you turn on the ac/defrost

 

[Mstng93SSP]

If I tap into an constant 12v source on the AC the electric fans will run constantly. I am trying to get them to kick on only when truly needed based on system pressure.

 

[Mustang5L5]

Edit: Nevermind, I reread what you wrote and now understand what you are trying to do. Disregard below then


That wire is not constant. It's the trigger wire to turn the AC on and feeds through the pressure switch.

In other words, it will only have power when you turn the HVAC controls to AC and command the AC to come on. It's not constant. From there, it feeds the AC pressure switch which opens and closes. Everything downstream of the pressure switch all depends on the condition of the pressure switch, and the WOT relay and will cycle the compressor based on those conditions. This is where you have your wire connected to now I assume and why the system is cyling the fan because of the nature of the pressure switch.

By tapping in ahead of the pressure switch, your DCC controller now will only see power when you select AC/Defrost and will not cycle.

Let me get a wiring diagram

 

[Mstng93SSP]

If it will give power only when the AC is switched on then the fans will run constantly as I literally run my AC 100% of the time.

 

[foxbodybill89]

Deleted- I also just got what you're doing. I have that controller also. If you're running A/C all the time though I can't believe you wouldn't need at least some fan all the time. I think you can set up the fan controller in the app to run low speed instead of high speed for A/C turn-on, might be wrong though.

 

[Mustang5L5]

Yeah, I get what you are trying to do now.

 

[Mstng93SSP]

My fan run as designed as far as engine cooling goes. By getting the AC power signal from the compressor the fans come on HIGH every time the compressor gets power and cycles. This is quite often. The way I understand getting power from a trinary switch the fans would only get power when the ac system reaches a certain pressure. The compressor could cycle 100 times before this pressure is reached. That would be 100 times my fans would cycle unecisarrily on HIGH causing the electrical load I am trying to avoid.

 

[foxbodybill89]

I would say just leave the A/C disconnected and let the engine temp strictly control the fan turn on, but the heat transfer from the A/C system might not be fast enough for the fans to respond....if you figure out how to get the pressure switch to work be sure to post, I might want to try that also.

 

[Mstng93SSP]

I know it can be done. It's how modern cars trigger their ac. Vintage Air also uses one on their systems for classic Mustangs. I am just trying to see if anyone has done it on a fox.and can show me how/where exactly the put the switch and how they wired it.

 

[foxbodybill89]

I looked at the link that karthief posted above, I wonder if the blue/white "fan relay ground" signal wire from the trinary switch could be used as the A/C signal wire for the fan controller....if it's just a switched ground might not give a 12 v signal though.

 

[KRUISR]

A quick question regarding how you are using your Contour fans for radiator cooling. Are you using just high speed or both the factory Contour speeds (low speed through the thermo resistor)?

If you are not using the contour thermo resistor, why not use that for A/C fans. You could wire it to operate independent of your cooling setup. Even if low speed runs 100% of the time, the power draw is less and to be honest, high speed on Contour fans is not needed to cool our cars.

 

[Mstng93SSP]

I agree we don't need the high speed. Mine is setup using the dakota digital fan controller. Wiring isn't exactly my thing so I simply followed the install instructions provided. It comes on low at the temp I choose and high the temperature I choose. AC compressor on simply turns the fans on high through the DD controller.

 

[KRUISR]

I am not familiar with how the dakota digital controller wired so excuse all the questions. Does the controller wire directly to the fans or through relays and then to the fans?

 

[Mstng93SSP]

The fans each have a relay. The controller turns the fans on either low or high at a temperature determined by the user via a bluetooth app. and off at another pre determined temp. The AC in on the controller just takes an incoming 12v and turns the fans on high. With it wired how they instruct you you tap the ac compressor wire so every time the compressor gets 12v to turn it on it also sends 12v through the wire you run to the controller and turns the fans on high. So the compressor cycling also y less the fans on high right along with it. With a trinary switch the 12v sent to the ac in on the controller will only happen when the system reaches a certain pressure.

 

[KRUISR]

So I understand... you have each fan on its own separate relay. The controller operates either in a low speed or on high speed. Is that correct?

Does it use the factory thermo resistor or somehow vary the power to the fans to get different speeds?

 

[Mstng93SSP]

Yes each has it's own relay. Controller control if low or high speed no factory thermo resister used.

 

[KRUISR]

Still trying to understand how the controller gives low speed through a relay without something to cut the power down (thermo resistor does this on a contour).



The first diagram is how the factory Contour system works. The second is how I hooked up my Mustang and my 2004 F150 with Contour fans (F150 used fans from a 2010 F150 with Contour control system and thermo resistor added as shown)