Thermostat problem?

[eeeric16]

Hey guys i noticed recently that my temp. gauge in the stock dash cluster is not working. It stays all the way on C even after long drives. When i pop the hood the engine is very warm and I'm not sure if my radiator fans are kicking on or not. I tested my sensor's sending unit by hooking a jump wire to the frame, when i turned the key forward the gauge did not change from what i understand from my Haynes manual, this means the sending unit does not need to be replaced. Does that mean the sensor is bad? Does places like NAPA have direct replacements? And also is there a possibility i could have a bad thermostat? Will the rad fans still kick in if its only the gauge not working? Sorry to ask so many questions in one thread but I'm worried about overheating my engine on a long drive i have planned this weekend. I appreciate anyone taking the time to help me out. Thanks

 

[GSXrestomod]

It doesn't sound like a thermostat problem. Id look into a way to test the guage itself, sounds to me like that's where the problem is. Get it warm and pop the hood while it sits and idles, watch to see if the fan kicks on.

 

[luv2rallye]

On a 1g the passenger side fan is controlled only by the thermo sensor/switch at the bottom of the radiator. The drivers side fan is controlled by the AC control unit. The dash temp gauge has it's own 2 wire sensor that has nothing to do with the fans (and is not the same one the ECU uses which is 1 wire).

 

[Jaxness]

If you have another 1g friend, swap out gauge clusters (make sure his temp gauge works) and see if it reads then.

 

[eeeric16]

okay, thats perfect answers - i'm putting a aluminum rad in this weekend so when i drain the coollant i'll put that sensor out and test it if that's not the problem it must just be the gauge

 

[9!'clipseDOHC]

On a 1g the passenger side fan is controlled only by the thermo sensor/switch at the bottom of the radiator. The drivers side fan is controlled by the AC control unit. The dash temp gauge has it's own 2 wire sensor that has nothing to do with the fans (and is not the same one the ECU uses which is 1 wire).

That is actually backwards.

On a 1g the sensor for the dash gauge, the engine coolant temperature gauge unit, uses a single Yellow/Green wire.

The engine coolant temperature sensor, used by the ECU, has 2 wires, one Yellow/Green (which goes to ECU Pin #20) and the other Green/Black (which goes to ECU pin #24, sensor ground). It doesn't matter which wire goes on which prong.

Neither sensor (both of which are mounted on the thermostat housing) has anything to do with the fans as the ECU has no control over the fans on 1gs. The fans are controlled exactly as luv2rallye described. So to clarify, the gauge not working has nothing to do with the fans.

Here's a diagram Brian (19eclipse90) made which should help visually with #4 being the temp sensor for the gauge and #5 being the sensor for the ECU:

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Hope this helps.

 

[luv2rallye]

Oops, your right. I had it backwards in my head - another 1am goof. Thanks for the correction (glad someone is checking me).

You can test the dash gauge by just grounding it's 1 wire sensor. With key on it should read max.

 

[fourgsixthree33]

Just get a new sensor (number 4 in the diagram). They are pretty cheap and should be replaced anyway. Also make sure none of the wires are broke or anything. This happens alot too because of corrosion.