using stock temp sensor for other fluids? how does this thing work?

a while back I got an extra stock temp sensor ('88 4.0) and plumbed it into my tranny cooler line. I then wired the original and new sensor to a switch, then continuing on to the stock guage. my reasoning was that with just the stock guage I could read engine and tranny temps just by flipping a switch.

anyway, I got it all hooked up, and the engine temp still shows normal, but the guage sits pegged at zero when I change to the sensor at the tranny cooler. Is there a reason a stock sensor wouldn't work in ATF? or does the sensor have to be grounded a certain way? how does the stock sensor work?

thanks
brett

The temperature sensor is a variable resistance unit, which presents a lower resistance with higher temperatures. It is also self-grounding, so if there isn't a good ground to its mounting location, you must provide one - a ground "tail" from the fitting to a convenient chassis ground should serve.

It is also important that the sensor is mounted so that it has free-flow over the measuring tip, rather then being stuck in a "pocket" - this is critical to getting an accurate reading. Using a pipe "T" fitting is acceptable, provided the hoses are connected across the "run" and the sensor is inserted into the "branch."

If you want an Excel sheet of specified measurements, hit me with an email and I'll send you a copy lifted from the 1990 FSM - I believe it's the standard GM sensor curve, so it should be compatible with most temperature gages. The IAT uses the same curve, so you can use an auxiliary IAT sensor to monitor ambient, "ram air," or whatever other gaseous temperature you like with the same gage and more switching.

Just for your reference, assume that any sensor you try to use with a single wire connexion grounds through the case and will need a solid electrical ground at its mounting point - so PROVIDE ONE! :lecture:

Just remember - pressure sensors can be mounted anywhere, but a temperature sensor MUST have live flow across the tip or you will NOT get accurate readings!

5-90

i have my gage out because im having trouble with it.i never moves even if i pull the wire off the back of the sender at the rear of my eng.(91 chero)i want to test it out of the jeep.there seems to be three connections at the back of it(the 3 screws)how can i check this gage out of the jeep?also what type of readings should i have on the printed circuit sheet that go to the back of the gage?im suspecting i have a bad ground because i had to run a seperate ground wire to the back of the cluster to get my gas gage to work.any advice is very much appreciated

ttt please help 5-90