Fan Sensor

[FMJ]

After 1500 miles of cool operation, my fan is not coming on until the temp reaches 100c. Everything seems in order coolant wise so all roads are leading to the sensor itself. Does anyone know the part number of this thing? Surely I can pick one up at the local auto parts store.

-Fred

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[Avalanche325]

Take it to any parts store. They should be able to match it up. Just make sure the temp range is what you want.

[Jeff Kleiner]

Fred!
You have a grounding switch like this:

https://www.summitracing.com/parts/bci-75029/overview/

This particular one turns on at 185F and off at 165 which should be a good match for your carbed engine. Not sure what stat you have but I'd suggest a 180. As I said last weekend I really recommend that you install a manual override switch for some "just in case" piece of mind.

BTW, did you guys cut out after leaving downtown London? I didn't find the car or you at the dinner or hotels. Good to see you again and thanks for letting me use your car as an example

Jeff

[FMJ]

That's the one! I knew you'd come through.

We left London about 2:00 PM and went back to the Holiday Inn. Your car was in from of the Fairfield and mine dead center in front of the Holiday Inn. Next year I'll do a better job of coordinating to hook up with you and other folks as well.

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[FMJ]

Jeff,

Replacing the switch did the trick. My fan is back to operating the way it was intended.

Thanks...

-Fred

[Svtfreak]

Is there a reliable way to test the switch? Immersion in hearing water with continuity meter attached? Mine never has acted right and fan never came on right (I wired manual switch in when I built as a backup) and I want to fix it when I rebuild the motor this month. I'm thinking I need a lower temp one maybe (like linked above) and pipe dope instead of tape (Yeah I should have known better). It worked when I first setup but hasn't since.

[CraigS]

How well does the 185 deg switch work. I have avoided it because, since it turns off at 165-170, I thought it would always be on after the first fan start. Figuring the engine will never get to 165-170 w/ a 180 deg t-stat.

[FMJ]

Can't answer that just yet. After installing the sensor most of my time was spent in the driveway with a few trips around the block. Once the temp was up and it was cycling on and off I put it back in the garage. I'll be out this weekend and get a better handle on how it works.

-Fred

[GoDadGo]

Fred!
You have a grounding switch like this:

https://www.summitracing.com/parts/bci-75029/overview/

This particular one turns on at 185F and off at 165 which should be a good match for your carbed engine. Not sure what stat you have but I'd suggest a 180. As I said last weekend I really recommend that you install a manual override switch for some "just in case" piece of mind.

BTW, did you guys cut out after leaving downtown London? I didn't find the car or you at the dinner or hotels. Good to see you again and thanks for letting me use your car as an example

Jeff

Jeff,

If I just ground it out can I assume that it will stay on with the key?
The engine will soon be in and I live down South where it is always pretty warm.

Steve / aka: GoDadGo

[CraigS]

Steve that will be fine as long as the power is coming from a switched source. Only potential problem I see is if you get into a hard start situation such as a cold morning. That fan draws a lot of current to be on at the same time you are cranking the engine.

[GoDadGo]

I'm using the Ron Francis Harness so I'm not sure if it is ahead or behind the switch.
The drivetrain still isn't in so I just don't know.
Thanks-O-Million!

[Jeff Kleiner]

Just put a manual toggle switch in parallel with the thermostatic sensor. I do this on all of my builds and it allows the fan to be controlled automatically or by the driver (useful in heavy traffic situations, etc. to be able to turn it on early before the thermo switch activation point when you know that the temp will be rising).

Jeff

[KDubU]

What Jeff says. Did that on mine and it works great.