Transmission heat problem

[jurick]

1997 Ford Explorer, 3" body lift, TT, and shackles

Well I had a problem today and it scared the crap out of me. I was driving home after picking my brother up from school and as soon as I started my truck up and started moving my transmission gauge started raising rather quickly and it was displaying a high temp the whole way home and I mean up to and above 200 degrees and when I got home it shot up to 300 and some degrees.

Now when I installed the temp gauge I also installed a cooler which normally keeps the transmission around 120-150. My question is, is it possible for the transmission to heat up that fast because before it would take a good 20 minutes of driving to heat it up. I started it up later in the day when it was completely cold it jumped up to 160 degrees in about 1 mile of driving. I am hoping that it is just a bad ground to the gauge but I dont know.

Any suggestions would be greatly appreciated.

 

[BrooklynBay]

Where did you mount the sensor?

 

[jurick]

It is mounted on the send line of the transmission lines the one carrying the fluid to the cooler but I have had this thing for at least 6 months and it has never showed a reading over 160 degrees and that was because I was towing a trailer. I am thinking that it has to be something with the gauge because it is electronically controlled and I dont think that transmission fluid temperature can raise that fast, or maybe it can. I don't know.

 

[BrooklynBay]

Does your sensor have one signal wire while the screw in base is the ground? It might have a bad ground connection.

 

[jurick]

Yea it has one signal wire and then the base is the ground. Hopefully it is a ground problem I think it might be up by the gauge though where I have a bad ground because I just recently tapped into the ground that feeds the gauge to feed another ground off of it for an illuminated switch so it may be bad continuity in there. At least that is what I hope it is and not my transmission.

 

[BrooklynBay]

Connect a jumper wire going to a good ground with an alligator clip (similar to a jumper cable), and test the ground when you see the gauge suddenly climb. It should drop down to a normal level when you touch it with the jumper if it's a bad ground connection. The jumper cable will provide the necessary ground at this point.

 

[Four0Sport]

sharing grounds is bad. its like sharing STDs. well not really, but still you get the idea.

 

[jurick]

Well thats what I kind of figured the problem was. It started after I installed that one switch for my emergency strobes that I put in. All of the switches that I have are illuminated and the electronically controlled gauges go though the same ground. The ground jumps off of the 12v accessory outlet. I know I shouldn't have it like this but it was a quick fix when I lost a ground last time and kept on forgetting to fix it.

 

[jurick]

Well I did some wiring today and installed a new ground just for the guage and the thing seemed to work fine but then I was going to go out and when I got halfway there it shot up to 220 degrees. So I went back to my house and got my tester out to try and figure out what the problem is.

After doing a lot of testing I have figurered out that I think that I might need a new gauge(even though this one is 8 months old). I believe that it is reading double the temperature it should be. I tested the voltage to it and that was fine the ground was also good, then I started testing the signal wire cable and this thing would jump from one voltage to another. At one point it was reading 9-10volts and then at another point it was reading 4-5volts and this happened several times within a minute and all I did was move the gauge.

So before I go buy a new gauge is there anything else I should check.

 

[BrooklynBay]

Are you describing the voltage swing coming off of the sensor? If so, then it might have a defective sensor.

 

[jurick]

Yes that is exactly what I am decribing but what has me confused is that if I move the gauge the voltage changes and if I tap the gauge while driving down the road it will sometimes jump up and then back. So my question is, is there anyway that the gauge could be causing the problem or does it have to be the sensor.

 

[BrooklynBay]

Tapping the gauge might mean that there is a bad connection, but there shouldn't be such a steep voltage swing. What brand is this sensor/gauge kit? It sounds like both might be bad.

 

[jurick]

Thats what I thought originally to that something was loose but all connections are fine. The gauge and sensor kit are the B&M kit from summit racing. It has been working since I got it but now it will either tell the real temp or double it. I was originally thinking that it could be the wire from the sensor to the gauge but if that wire was broken it wouldnt cause the voltage to be exactly doubled. I am just confused because this started after I installed my emergency strobes but I never touched any of the wiring for the gauge except when I installed the switch. All connections are fine though.