Electric fan temp. probe location

So I have a screw in 1/4"NPT temp probe for my electric fan. I can either put a Tee in the head where the heater hose connects (not exactly in the water path unless the heater water valve is open), a Tee where the water temp gauge fits (thought this would pull the Water temp gauge probe out of the direct water path) or I can put it in the block petcock valve location.

Any thoughts? I have an expensive stainless fitting for the heater connection and hate to replace it. For the rare occasions I would open the block petcock

Edited by Mark W. - 20 May 2017 at 10:10pm

When we started seeing electric fans on Chevrolets in the '90s, the sensor for the fan was in the radiator, and I saw them there on other vehicles as well. Seems to me, when the coolant in the engine needs to be cooled the thermostat opens and sends the hot coolant to the radiator, trading it for cooler coolant from the radiator. When the coolant in the radiator is hot, that's when you want the fan to run. If the sensor is in the engine, when the hot coolant is replaced by cooler coolant from the radiator, the fan will stop, and not cool the hot coolant in the radiator. 

My 3B actually runs a real 225 V6 radiator now and the converted I4 unit did work, sort of..
I have a 13" electric fan mounted in front of the radiator with an on off switch on the dash. The fan also has a variable switch so you can control when it will come on. I found no place to put the sensor inside of the motor as it is sort of too long and it works fine Zip tied to the top of the fins on the radiator and then just adjust it to where you need it to come on. There was no way I was going to cut into a hose to stick it in and then deal with a leak.

Thanks for the advise guys. Bruce I think your idea is the best one going. In the past the sensor probes I have dealt with have all been contact style. Where I attached them to the radiator just touching the bottom of the Top tank. I guess I will add the hassle of getting a proper aluminum bung welded to the back of the Top tank as close to the bottom as possible.

As to the switch comments if you check out my Project thread on Chug I built a switch that will control the Fan from the dash. It has three settings ON automatic controlled by the sensor ON manually and then OFF (for water crossings etc).

Yea he uses a DPDT toggle switch I have chosen to use all Polack push pull switches with stock looking knobs. So I had to make a switch that would do what I wanted (the same functionally as his just different cosmetics and operation.




I reversed the operation of a OFF/ON/ON two position push pull switch so it operates as ON (in this position automatically based on the temp probe) ON (manually no matter what the Probe says) and all the way out is OFF (for water crossings etc.)

 If it were in the block, you would have to set it 15 to 20 degrees over the operating temperature  of the engine so that it wasn't coming on all the time.  If it were in the block and you set it at the engine operating temp....it would run whether the radiator was actually warm or not.

Yes I used the threads for the original knob.