Was going to run an electric fan instead of the stocker, mounted it all up got it all wired, problem is the thermostat switch that came with it is the type that just pushes between the cooling fins on the radiator. If I hold my heat gun on the "probe" it will come on...but with just the truck running it does not come on and the truck will over heat. What do you recommend ? Is there a different way to mount the probe so it gets an accurate reading of temp?

Get one that actually screws into a water passage.

That way it will be reading the temp of the coolant and be more accurate.


This is the way I plan on doing the 72 charger when we finally get it on the street.

I had one of the rubber expansion type ones on my Buick GS, that go where an expansion plug is, but now that I'm looking I see some on ebay that look like they might screw into the intake... anybody use this kind? Just trying to not make a huge mess with anti freeze now that I just filled this beast up.

Thse are what I'm looking at doing.


Pick your poison

Depends on what your themostat opens at.

I don't know what fan you are running but I use the Ford Taurus 2 speed fan with the Dakota Digital fan controller in my 72 Challenger with a 512. The Dakota digital unit uses the existing gauge type temp sensor and fan on and fan off temps are adjustable for both speeds. Thay are a little spendy but they caome with the relays and are well worth it.

I used an adjustable fan thermostat that I got from Summit (Hayden Automotive 3653, for 23 bucks), and then wired that into a relay so that the high current for the fan is not running through the thermostat.

The problem you may be having is that the probe is not picking up the correct temp from the radiator, so it never actually gets the probe to 185 degrees and the fan never turns on. Mine also has the radiator probe, but since it's adjustable, I was able to tune it so that it turns on when I want it to. That way it doesn't matter what temp the probe is actually getting to, I've got it set so that the fan comes on when my engine gets to a certain temp. The radiator may only be heating the probe up to 150 degrees when the engine temp hits 195, but since I can adjust the thermostat, I just adjust it so that it turns the fan on at that point.

I originally wanted to use a probe that would screw into a coolant passage, but I could only find one spot to do this on my intake, and the temp gauge for my instrument panel is already screwed in there, so I went with the radiator probe and adjustable thermostat instead. So far it has worked flawlessly.