Is this a bad thermostat or engine temperature gauge problem?

1990 NISSAN 300ZX
147,000 MILES
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WEVERETT
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  • 2 POSTS
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?
Jun 22, 2012 at 4:42 PM
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DOCFIXIT
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Suspect cooloing fan or radiator effeciency reduced to calcium buildup in core
Jun 22, 2012 at 4:47 PM
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KHLOW2008
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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.
Jun 23, 2012 at 3:07 PM
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TIMHILLMER
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most likely this would be caused by a bad ground connection.
Jul 15, 2012 at 9:28 PM
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WEVERETT
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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.
Jul 16, 2012 at 10:10 PM