Ok..I have a B&M Hitech Trans cooler with the fan on it... I have a autometer trans temp sender unit in the hott line coming from the cooler/heater tube below the turbo... I have seen temps at 200 degrees and my fan will not kick on... I have a little LED light mounted next to my guage that is supposed to come on when the fan is on... So, I pulled of the plug that goes to the thermocouple on the cooler, hooked up a jumper wire between the two and the fan works great, the LED comes on just like it should... So, I called B&M told them the deal we came to the conclusion the thermal switch must be bad... Put the new one in and same thing....

So.... I am starting to think about the guage being off or something... Anybody have any ideas??

Here is a few pics of the setup

 

i have the same prob one day while wheeling it came on at 175 and never let it get aboue 175. but today i saw 220 while wheeling and no fan ***.

 

I have a similar one on the drag truck. I don't think mine comes on until it is over 200*. What did they say was the set point for when it would come on? My gauge uses the sensor in my cooler. That may make a difference on the temps we are seeing too?
Is the thermocouple reading post cooler temps? Maybe it is cool enough after the cooler not to come on and you are seeing the temps high before the cooler? IDK, throwing things out there.

 

well the thermal couple is at the back of the cooler on the inlet side. My trans temp sender is about 6" before the inlet. I am gonna try and use a infared heat gun to see if I can get any kinda reading. I'm kinda baffled. Never had a problem with the same setup on my wheeling truck in three yrs.

 

It almost sounds like the gauge is off or something. How often do your temps get up to 200? With the weather being cooler now i hardly ever see it that hot. Normally 150-170. Even when i plow i will not see temps above 200 expect when pushing up a steep hill. I know you said that your 47rh was slipping a little is it that bad it would make it be that hot?

 

Well, I have the raditor fully blocked and on a warm day 40+ stop and go I can get the temp guage around 200.. I have to sit for a bit with the brake on and a little go peddle to get it warm... I've done it on purpose just to see if i can get it to kick on..