Hello all: I am changing from the radiator probe type thermo control to a three prong vw ground activated thermo switch. I am currently using this wiring:



Is it possible to run the ground from both relays through the ground terminal on the switch, and low speed, terminal 2, would go to ground, completing the circuit? Is that kosher?

 

But what are you trying to accomplish by doing that?

 

My radiator probe caused the radiator to leak. So I am trying to find a trigger that will be dependable. Hence the VW Audi thermal switch in the radiator line.

Is there/would there be a problem wiring it that way? Doing it that way mean not having to rewire the entire system. The VW switch is ground activated. Or would it be better to run the fan grounds through the switch?

Thanks for the reply. After doing a bit more research on various online articles of 'how to', I have found that triggering the ground is a fairly common way to wire it, and actually the recommended method. Cheers.

 

Run the relay grounds through the switch , not the fans. The fans likely pull too much current and will fry the switch. That is why there is relays on them in the first place. I want to see pictures of this setup when you are done. I want to go electric with fans automatically turning off and on.

 

I am still using the diagram I posted. The changes will be the keyed 12v will go straight to the relays since I'm deleting the insert type adjustable control. The probe put a hole in radiator! The other change is I'll be using high/low VW/Audi thermo switch in the top radiator hose, and the relays will ground through that switch. You can also drill/tap your thermostat housing and install the switch there. It is M22 x 1.5 threads.

I have dual fans and wire them independently so if one fails I still have cooling. I also have a back up/spare switch, one in the radiator hose, one in the thermo housing. I use the fan out of a Ford Contour/Mystique, with the 16 valve engine. It moves 3500 cfm. I took the relays from a Taurus.

If you search the forum under Contour fan, you'll find the thread. I would convert to the 3g alternator from a Taurus first.