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Discussion Starter · #1 ·
Hello my fellow Pontiac Owners,

I need some help understanding my electric fan temp switch. So I purchased a dual electric fan setup from Champion for my 71 lemans 350 with what they say came with a temp switch that is supposed to turn on at 185 degrees and turn off at 165 which would be a 20 degree window but something is off. The dual fan kit came with 2 relays which I spliced into each other so they come on at the same time and I am only running one temp switch on the intake manifold. The problem I am having is that the fans are turning on at 200 degrees and turning back off at 190 degrees, which concerns me.

As the KIT came with two temp switches I have tried both and both come on at 200 and only drop to 190. I would not mind if they turned on at 200 and dropped to 170 but I am worried they are only dropping 10 degrees causing my fans to work harder.

I am running a 160 degree thermostat, could that have something to do with it? As for the temp reading I am running an Autometer sport comp series gauge which is about 10 years old which is also connected to the intake.

I also installed a new 150amp alternator to handle the amperage but the issue remains the same.

Do you guys think I should install an adjustable fan control switch? If so what is a good brand? I know at 190-200 I am still not overheating but I would like to car to stay in the 185 and below range if possible.

Any help is appreciated so thank you.
 

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Make sure your temperature reading on the gage is correct. I double check mine by using a temp gun at the intake near the thermostat housing (and/or next to your temp switch). So long as they are within 5 degrees or so, I'm happy.

Otherwise, I would suspect your temp sending units are off and I'd contact the seller. A different controller may be an option if the seller can't/won't help. I have a Derale controller on one of my cars that is adjustable. I like that fact, but cannot give them a great reference since the first one did not work out of the box and within 10,ooo miles had to replace the relay and buy a spare for the glove box.

I'm not sure how you "spliced your relays, but don't think that would affect the trip points of the temp switch.

The only other thing I can think of is that there may be a real 15 degree difference between where your gage sending unit is and the fan temp switch.
 

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Discussion Starter · #3 ·
@Sick467 thank you for providing some suggestions Noel! Ima go ahead and check with temp of the intake while running near the temp switch and gauge temp sensor to see what readings I get.

when I say I spliced the relaysI meant I basically spliced the temp wire, power wire to battery and ignition wire from both relays into one and connected that way.

the temp switches could be defective but it’s hard to think both temp switches would be.

I think it might have something to do with the 160 degree thermostat I am running. I am not sure how but I think since it opens up at 160 it keeps circulating through the radiator and back into the engine multiple times and by say the 3rd or 4th time the temp reads 200 they turn on. Do you think switching to a 180 thermostat might fix it?
Thank you!
 

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I don't see how a 160° thermostat could affect it. If anything, it should make your fan switching more stable at the point they open. Meaning, the engine warms up to 160°, the thermostat opens which dumps a load of cooler water into the engine, which cools the thermostat, which shuts the thermostat momentarily, which heats up quickly and opens the thermostat again. I suspect this happens at least once, maybe twice. Now, the temp of all the engine coolant gets past the 160° mark and gradually approaches the 180° mark (or whatever temp mark the fan switches are). This would keep the fan switch from fluttering once or twice. Not a big deal either way, but my point is that the thermostat would not be poorly affecting the fan switches to come on/off at the wrong temp.

I use 180° (or higher) thermostats in all my V8's except the one that has the electric fans ([email protected] 289 stoked to a 331). The thermostat is 160° and the fan switch is set to kick on at 180°. If this were a car that was driven in the winter, it would have a 180 in it to help with the heater temps. It does get to the 200 plus mark in slow traffic, but will hold 180/190 on the highway and 160 in the cooler weather.

Here's an easy test. Hot wire the fans to run 100% of the time. Start the engine and watch the temp gage. You will see the temp raise until the thermostat opens, then it will drop just a bit (or stay at about 160° for that bit) and then continue rising until it gets to the point that the system will handle. It will stop rising when the fans and radiator are doing all they can to cool it. In other words, it hits "steady state". So long as that is not too hot for your liking and your fans come on before it gets too hot...your system is working well. If it gets too hot for you , then the system is not designed to handle the load. The above test is at an idle on a hot day in the driveway. Moving down the highway will cause the engine to produce more heat, but the air moving into the radiator from the motion of the car will exceed your fans and cause more cooling than you get in the driveway. You should see cooler temps on the highway compared to stop and go traffic.

I suggest verifying the temps of the thermostat housing, temp switch location, and gage. If they are all close together, suspect your switch, but it may not be a issue if they keep your car from over heating they way they function now.
 
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