Mechanics

IS THIS A BAD THERMOSTAT OR ENGINE TEMPERATURE GAUGE PROBLEM?

1990 Nissan 300ZX • 147,000 miles

I have a 300ZX with 147,000 miles. When turning on the air conditioning, the engine temperature gauge rises to the top. When I turn off the air, the temp drops back to normal. Is this a bad thermostat or engine temperature gauge problem?
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Weverett
June 22, 2012.



Suspect cooloing fan or radiator effeciency reduced to calcium buildup in core

Docfixit
Jun 22, 2012.
If the gauge shoots up immediately and cooling fans works, it would be an inaccurate reading due to a bad ground circuit connection, behind the headlights.

KHLow2008
Jun 23, 2012.
Most likely this would be caused by a bad ground connection.

Tiny
Timhillmer
Jul 15, 2012.
Thanks for help. Replaced clogged radiator, power washed the air conditioner condenser. I could not believe the road crud that washed out. While I was there I replaced the hoses and thermostat. To my surprise, the thermostat had been removed. There wasn't one. I bought this Z used. Previous owner must have had overheating issues as well. Not sure what fixed the problem ( maybe all of the above) but temp gauge is level no matter if air is on or not and it is 110 degrees out.

Tiny
Weverett
Jul 16, 2012.