water temperature gauge problem

[funkysandman]

My gauge says the engine is always cold. I replaced the sender and no change, and if I short out the connector the sensor, the gauge needle goes all the way to hot. The fuel gauge is working. This is an 85 CJ with a AMC 258 i6 / 4.2l . I used to have a 4 cylinder (temp gauge worked) and swapped in the AMC 258 i6 / 4.2l . The temp gauge has never worked since. Any ideas on how to fix this?

 

[funkysandman]

ok, I think it's just the wrong sending unit. I took the resistance when the engine was warm and it was about 360 ohms (should be 10 times less). My AMC 258 i6 / 4.2l is from an 89 YJ - the sensor for an 85 YJ has a slightly different product number, so they must work with different gauges. I will try to get the new sensor and post back my findings. btw, I couldn't use the sensor from the I4 because it didn't fit.

 

[BusaDave9]

Are you sure the engine really is getting up to temp? Does your heater blow hot air? You may not want to warm up in the summer but it could tell if your coolant is circulating. If not it could be a bad thermostat.
You are probably on the right track with the sending unit but I just wanted to throw that out there.

 

[funkysandman]

The engine overheated the other day - I was truly low on coolant- the gauge showed nothing... it never moves. Thanks for the input - I believe the t-stat is working - no coolant was circulating at startup...

Are you sure the engine really is getting up to temp? Does your heater blow hot air? You may not want to warm up in the summer but it could tell if your coolant is circulating. If not it could be a bad thermostat.
You are probably on the right track with the sending unit but I just wanted to throw that out there.

 

[mtnwhlr]

I would try getting a sending unit for a '85 and don't use any kind of tread sealent on it when you put it in.

 

[funkysandman]

this is exactly what I'm doing...thanks

I would try getting a sending unit for a '85 and don't use any kind of tread sealent on it when you put it in.

 

[funkysandman]

ok, i installed the sending unit for that year.
The gauge needle moves, but it just reaches the start of the green area and never goes higher...I'm sure it supposed to be a little bit more into the green

 

[BusaDave9]

No, I think that's good.