OK; Before I get flamed for being a hacker,... I already know !!

I was having trouble with a cooling fan that would not operate properly. The car is an 87 Carb car with factory electric fan. The engine swapped into it was from an 87 TPI with a single electric fan,..../ meaning that it did not have a head mounted fan switch from the factory. When the engine was swapped the plug in the pass side head wasn't "easy" to remove so it was left in place and the fan sensor was mounted in the intake port.

The Cooling fan would operate when the switch's plug was manually grounded or when the HVAC controller was moved to an AC setting; but would not operate by the switch alone. I replaced the switch with another ( used ) one and the fan still didn't work,... then I replaced the switch with a new one and the fan still didn't work. Seems as if the intake coolant wasn't as hot as the head coolant. I didn't know if the 2 used sensors that were used were good or not - but the new switch was new and I felt it was reasonable to assume that it was OK.

SO; the HAVC controller was OK, the fan was OK, the fan relay was OK and the wiring was OK, but I had no way to check the switches, so I got creative




The voltmeter was used simply to be sure that my hack wiring was OK. I used a couple jumper wires, a test light, and a plumbers torch to test the switch. The switch was grounded with a jumper wire. The test light was wired to a hot wire on the positive side and the ground was jumped from the PIN on the fan switch. I then used the torch to heat the sensor ( slowly heated by waving the flame back/forth over the sensor. )

The 2 used switched I had tried in the intake were checked first and they both failed. The plastic plug end melted and fell off the switch before the light ever turned on. I still wasn't sure this test would work and didn't want to ruin my new "low temp" fan switch - so I found a third used sensor in my tool box and tried that, the 3rd used switch is what is shown in the pic above. After heating the switch for a little while -----> the test light turned ON !! ( SEE PIC ) I removed the heat long enough for the light to turn off and then heated it again and took the pic the second time it came on.

Since I was working on the 87's exhaust system I pulled the pass manifold to gain better access to the pass side head switch port and was able to remove the plug and install the 3rd used sensor. Once the entire exhaust was replaced and the engine was re-assembled I let the car run and get hot and @ about 240 degrees,........ the fan actually worked as it should !!

So; it might be a 'hack', but at least I know that it IS possible to test the switch with a torch, a test light and a spare wire or 2 !