Is this a bad thermostat or engine temperature gauge problem?

WEVERETT

MEMBER
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?

Friday, June 22nd, 2012 AT 4:42 PM

4 Replies

DOCFIXIT

MECHANIC
18,828 POSTS

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

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Friday, June 22nd, 2012 AT 4:47 PM

KHLOW2008

MECHANIC
41,815 POSTS

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.

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Saturday, June 23rd, 2012 AT 3:07 PM

TIMHILLMER

MEMBER
7 POSTS

Most likely this would be caused by a bad ground connection.

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Sunday, July 15th, 2012 AT 9:28 PM

WEVERETT

MEMBER
2 POSTS

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.

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Monday, July 16th, 2012 AT 10:10 PM