Dual temp sender

[Interceptor5588]

I'm setting up dual electric fans on the GTO. Is there any such thing as a 2-prong temperature sender (NPT threaded into the manifold) that would signal the two fans to turn on at 2 different temperatures? Say, 180 and 200 degrees.

[andrewb70]

I'm setting up dual electric fans on the GTO. Is there any such thing as a 2-prong temperature sender (NPT threaded into the manifold) that would signal the two fans to turn on at 2 different temperatures? Say, 180 and 200 degrees.

Temp sensors don't generally trigger the activation of fans. They are thermisters where the resistance varied as the temperature changes. That signal must then be interpreted by another box (ECU or fan controller), which then sends a signal to turn the fans on/off.

Andrew

[cornfedbill]

Temp sensors don't generally trigger the activation of fans. They are thermisters where the resistance varied as the temperature changes. That signal must then be interpreted by another box (ECU or fan controller), which then sends a signal to turn the fans on/off.

Andrew

Some of the old sensors were bimetallic and switched at a certain temperature (before ECU's). I have never seen one with more than one temperature output though.

[jwatts]

Short answer, yes. There were certain year BMWs that used a single sensor to trigger 2 fans. I have this setup on my Chevelle. You will need to determine the temps you want the fans to trigger at to determine which sensor to get. There were a few that triggered at different temps. Here's a link to another site with a pretty detailed thread on the parts needed.

http://www.nastyz28.com/forum/showth...fan+controller

Edit:
I guess I should also add that these are an oddball metric thread. You will likely have to either get an adapter to adapt to the threads that are in your engine, or turn the old threads off of the sensor and re-thread the correct threads for your application.

[dontlifttoshift]

Dakota Digital fan controller. It will run both fans at separate and programmable on/off temps. It uses the signal from your existing temperature gauge.

[H2Ogbodies]

Its far more efficient to run them both. It makes absolutely NO sense to run one fan, then the other. Having said that, I would suggest assembling a 2-speed relay harness so you can run them both in series for low and high speed. To my knowledge, no controller can be used with fans wired in series but the benefit is the simplicity of it, parts can be found at any parts store (so no worry of "design changes" or 15 versions of a controller, only to go dis-continued). And, it is a stand alone setup using GM style switches which are a proven reliable design.

[MonzaRacer]

For me in GM cars, like SBC,BBC use old school temp sensors for tpi. Msd and jet used make them in different temps. If you want fans at two different temps you should use the two different switches and relays. NEVER try to run fans direct from switches.
I use the oval gm relays as they work well under heavy loads.
And don't burn up easy.
Use the switches to run relays.
My personal preference is to run fans full speed, if you run two fans at two different temps I would use the high temp one for ac too.
There are several ways to wire this set up. One relay to run one fan one for another OR one for one fan and one for both fans.
Use 18 guage wire fused to relay. Ground through switches. Run 10 ga fused to fan relay then to fan.
Or 8ga fused from battery to relay then single trigger wire to relay.

[dontlifttoshift]

Its far more efficient to run them both.

Do tell.

It makes absolutely NO sense to run one fan, then the other.

If I only need one fan, it makes no sense for the other one to be on. Seems like it would be most efficient to use the least amount of power as possible.

Having said that, I would suggest assembling a 2-speed relay harness so you can run them both in series for low and high speed. To my knowledge, no controller can be used with fans wired in series but the benefit is the simplicity of it, parts can be found at any parts store (so no worry of "design changes" or 15 versions of a controller, only to go dis-continued). And, it is a stand alone setup using GM style switches which are a proven reliable design.

I would love a part numbers for the GM switches that are in stock at every parts store and will match up with whatever thermostat I decide to run. Then where should I mount it? I have two holes in the intake, one for the heater and one for the gauge sending unit. Should I put the fan switch in the head? Wouldn't it be cool if I could use the sending unit that was already there.....kinda like GM does now? Yes there have been revisions on the PAC module, I have had zero failures in approximately 75 units sold and installed. Guess how many switches I have thrown away because they turn on before the thermostat opens and never shutoff.

Serious questions, how would you wire a two speed relay for a single speed fan and what is the advantage of wiring the fans in series?