Coolant Temp SWITCH questions...

[Mike Braddock]

Greetings again from sunny Florida.

I'm trying to finish the wiring on our car and one of the last things is wiring up the electric fan switch and coolant temp warning light. I've seen the switches that mount in the radiator fins (actually I bought one) and inside a water line and I don't care for either of those. So I thought the best would be to copy what the factory did and install a simple coolant temp switch to control these two items. And this is where my problems begin .

I'm having a hard time finding information on coolant temp switches and was hoping some of you could help me out. Specifically, I'm trying to locate information that cross references sensor (switch) part numbers, closing temperature and NPT thread size (ie 1/4", 3/8", 1/2" NPT, etc.). But this information is much harder to find than I thought it should be ! The guys at the parts houses can't give me the switch closing temps, so I can't just go into NAPA or AutoBone and ask for a coolant temp switch with a 200*F closing temp and be on my merry way--NO, that would be too easy .

Originally I was thinking I would like to have the fans turn on around 185-190* and have the warning light come on around 210* to draw my attention before it's too late. Are these reasonable temps? I've read that 230* is about the highest temp you want to see before you shut the engine down. Does this sound reasonable to you all? And I think 180-190* is a reasonable coolant temp during normal driving conditions?

SO...can anyone tell me what temp sensor(s) they are using (ie model number, donor vehicle, or the like), what temp they switch at and what NPT thread side they require? Thanks so much.


Originally I was just going to try and find the PN's for the two switches I need but after spending all day yesterday looking for this information on the net and at local autoparts stores, I would really like to begin compiling a list of sensors that we can post for anyone who needs this info in the future. Here's an example of the information I am hoping to collect:

Donor vehicle: Closing Temp (*F): NPT size:
Pontiac Fiero 235 1/2"
Ford Mustang (4 cyl) 200 ?
'86 Buick Grand Nat'l 190 ?

etc.

I will post any additional information I find as well. For my 351C I'm trying to find a switch that has 3/8" NPT threads as well. Thanks again.

Mike

PS Here's a company I found that sells the switches I'm looking for, but I really wanted to buy OEM switches that could be replaced at any auto parts store:

http://www.electricfanengineering.com/dyno-tro.htm

[Jack21]

This may, or may not be the answer you wanted but...

Got the fan sender, connector, and fan control relay from Ron Francis Wire Works.

The fan sender, a 180 deg unit, went into its own drilled & tapped hole in the intake right next to the temp gauge sender, and right over the water jacket outlet in the head. The on & off temp values came with the kit. I remember checking it on the stove with a pot of water and a meat thermometer before installing it, but don't recall what the values were.

The power in side of the relay takes +12v off the power grid and has its own circuit breaker. Power out goes to the fan. The control side takes power off ignition, and completes the ground through the fan sender. Also have another complete the ground through a dash switch for getting stuck in traffic.

With 180 thermostat, gauge stays right at 180. In stalled traffic, I use manual override when gauge goes to 200 - 210. Fan will cycle on and off otherwise.

You could install a temp warning light, but that's what the gauge is for. You could use a hotter sender in the thermostat housing for a light.

[Rick Parker]

I recently was redoing the cooling fan and electrical system supporting it. After looking at the switch specifications in the back of the catalogs at NAPA, I was unable to find one smaller than what I am currently using that had the temp setting I wanted. I an currently using a switch sourced from VW (Bosch), I think it fits a VW Rabbit or Golf. I was attempting to find a smaller switch (currently 22 mm thread) with two terminals but everything listed had a higher closing or opening tempratures than what I was comfortable with. That agrees with the fact that most of the later model cars that actually have electric fans operate at higher tempratures, many at or above 200 degrees, leaving a very narrow margin for overheating and coolant loss therefore 15-17 lb radiator caps, and sealed cooling systems.

......Rick

[PNJSNAK]

Fan Switch:
Mike; I used an electric fan switch assembly from American Autowire Systems in N.J.
The switch threads right into the Themostat Water outlet and wired to a relay under the dash. It is set to turn on the fan at 195 and off at 180. Works like a champ.
Phone number is 856-933-9301.
This company makes the wire harness kit for Ron Francis.
Good luck.
Jim

[Mike Braddock]

Thanks guys! Lots of good info. I'll call and see if I can buy just the switch. Have a great weekend!

Mike