I swapped a rebuilt motor with analog temperature gauge into a better body car that had a digital gauge. The digital gauge worked in the car before i swapped in the rebuilt motor. The gauge did not work since the sending unit on the rebuilt motor in the digital car was from an analog car. I put in a new digital sending unit from the dealer. Now the gauge shoots to the top of the scale(270 degrees), even when the car is cold. I know it is not overheating, but something is wrong. I thought maybe a ground was loose. I have nothing else that is acting crazy like a/c, blinkers, dash lights etc., the crazy stuff that happens when grounds are loose. My digital speedo doesn't work, but it didn't work with the old motor either. I was sure once the digital sending unit was put in, it would work perfectly. Any clues?

 

sounds like a faulty sender. Take it back to the dealer and tell them it's faulty and get a replacement and see if that fixes your problem.

 

ground the harness connector, does the gauge reading change? also leave it disconnected, does it change the reading? wiggle the wire and see if that helps. You probably just need to replace a few inches of wiring. It wouldnt hurt to check the sending unit with an ohmmeter if results with the wiring aren't definate.

 

Actually it sounds like you have a short to ground. if it is shooting all the way up it is showing no resistance and just showing volts suplyed. if it were going through the sensor when the car was cold meaning temp down the resistance would be up, and when the car is hot temp up the resistance is down. It should be a negative coefitiant temp switch. NTC(NCT)

 

I don't know how to ground the harness connector. When i cut off 4" of wire and replaced the connector, nothing changed. Of course it reads nothing when it is disconnected. I just came home and went out to the car and switched it on and it shows that it is overheating, but it has not been running since last night. I have the splice area where I spliced in the wire and connector, do i ground from the splice to the frame ? or if i do, will it blow a fuse? I know just enough about wiring to fry my wiring harness. Thanks.

 

I think the dealer sold you the wrong "digital sending unit." Do you have the old one still???

 

Well even if you don't get it to work at least your talking lady will...check your PM...

 

Yes, i have the old one and it looks just like the new one. First off he ordered one that it said was digital, but it was smaller than the one for my car. The digital sensor and gauge worked in the car before the motor swap. I pulled the digital sensor out of old motor,to show the dealer what the right one looked like. The analog sensor did not work, went to the top and now this one does the same. I may have to put the one from the digital car in to see if that has any effect on the gauge, but those things are a pain to put in. I still have some concerns because i can jiggle the wire and the gauge flashes on and off but the connector and wire are tight. Someone suggested that it may be the digital dash needs replacing, only the gas gauge works correctly.
And yes, Thxone I saw the PM, thanks, and welcome to Georgia, even though it is just over the line in flat land. You are about 200 miles away from Albany. Well, i hate to but i may have to take the car to the dealer if all else fails, but a friend of mine owns the dealership and he is the one that got me hooked on Z's. Thanks.

 

That would have been the first thing to do....

 

Ground between the gauge and the ground. But the fact that when you disconnect the wire from the sender causes the gauge to go back to zero tells me it's most likely the sender, as mentioned earlier. Take the one you bought back and get it replaced.