Cooling fan switch ??
If you live in a hotter climate like we do here in Houston I would run the fan relay off the ignition switch. Most of those temperature switches don't work well without a computer telling the fans when to come on.
I built a nova with a 750 hp 421ci small block with dual fans and they run all the time even in 50 degree weather and the car runs fine. If you put it on a manual switch you will eventually forget to turn it on and like I said those temp. switches are not reliable.
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You can also thread, 1/8" npt, the end of a standard set switch.
If your using a large Sender, you can try using the water pump, the flat area about the outlet. Just drill and tap it
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This Fan-Thom II kit comes with a threaded thermostatic switch that screws into the extra coolant temperature sensor port of the passenger engine head on Generation III and up GM engines for a professional looking installation. This is inexpensive protection for an electric fan and a vehicle's wire harness. Provides constant voltage, protects from voltage and amperage spikes and prevents the fan from back feeding voltage through the vehicle's wire harness.
This kit includes:
SPST 40 Amp relay
30 Amp circuit breaker
12x1.5M Thread Thermostatic switch 205°F On/190°F Off
Relay base with harness
Crimp-on terminals
Mounting hardware
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I have used spal for years and never had to worry about quality or reliability.
Tim
DO NOT INSTALL THE RELAYS TO ENGAGE WITH THE IGN SWITCH YOU WILL BURN OUT THE FAN MOTORS QUICKLY WITH CONTINUOUS USE
That painless temp switch looks to be the ticket to me. At one point they sold just the switch for $35. Now they only offer it with the relay and wiring kit. Overpriced.
You actually have several other options.
The previous posts list several other places you can fit a larger sensor into a radiator hose or even the top of the water pump housing.
There is a member on here who takes 3/8 or 1/2 in temp sensors and turns them down in his lathe to fit the metric head. He can easily do that with a temp switch too.
You can also drill and tap the head to be 3/8 NPT. A very common mod on here. Both heads have fittings, so you can put it on either side of the motor.
Another option is to drill and tap the brass block heater plug in the side of the block. That is what I did to fit a Datsun sensor. Here is a picture of how to do it.
https://ls1tech.com/forums/album.php...ictureid=55426
Last edited by Pop N Wood; Mar 10, 2011 at 02:58 PM.
https://www.scramspeed.com/products/...witch-180.html
Last edited by BlackWS666; Nov 12, 2019 at 10:04 AM.










