1986 Volkswagen Jetta Temperature Gauge and Overheat Warnin

Tiny
STEPHSKI
  • MEMBER
  • 1986 VOLKSWAGEN JETTA
  • 4 CYL
  • 2WD
  • MANUAL
  • 230,000 MILES
Over the past year, my temperature gauge and overheat warning light have been indicating overheat problems with my car (it's not my daily driver). So far, we have replaced the thermostat, the water pump, the radiator, the sensor that the gauge plugs into in the block, and an electrical relay switch. We are still having the same problem. After running a while, when I check the block temperature (with an "aim-at" remote sensor), the external temp is about 190 degrees. The car has also been checked for head gasket issues, and we're told there's no problem there. HELP--any thoughts you have would be greatly appreciated!
Thursday, April 2nd, 2009 AT 7:54 PM

7 Replies

Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
Is the over temp light on all the time when the engine is running?
Is it intermitent?
Does it matter if the engine is cold or at running temp?
Please advise.
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Friday, April 3rd, 2009 AT 1:57 AM
Tiny
STEPHSKI
  • MEMBER
  • 5 POSTS
The light is completely unpredictable; sometimes on from the word "go"; sometimes after a few minutes of running; sometimes (although rarely) not at all. So, no, it doesn't matter what the temp the engine is. Thanks.
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Friday, April 3rd, 2009 AT 4:08 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
Try unplugging the gauge temp sensor and leaving it unplugged for a day or two while driving it normally. I'm confident it's not an overheating problem. It apears the gauge and light are just lying to you. Baaaad light, bAAAAAAd light. If the light still goes on and off with the sender "disconnected, something in the wiring, and very possibly in the instrument panel, is grounding the circuit. Let me know.
One more thing, IF, after a day or of driving with the temp sender unplugged and the light DOESN'T come on, try grounding the temp sendor connector. Then the light should come on. Again, let me know.
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Friday, April 3rd, 2009 AT 7:17 PM
Tiny
STEPHSKI
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  • 5 POSTS
I'll give it a shot and let you know. I'm at my wit's end! (Love the humor by the way--TX!)
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Friday, April 3rd, 2009 AT 7:38 PM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
Just happened to be in the area and was wondering how your temp gauge problem came out.
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Monday, April 13th, 2009 AT 8:56 PM
Tiny
STEPHSKI
  • MEMBER
  • 5 POSTS
Your checking on my status with this issue. To be honest though, I haven't even tried to do what you suggested. I've just chosen to ignore the flashing light when it happens.

It was a real pleasure using this service and getting your assistance.

Thanks again!
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Sunday, May 10th, 2009 AT 9:20 AM
Tiny
STEPHSKI
  • MEMBER
  • 5 POSTS
I thought you might find this of interest. I checked the oil this weekend in my Jetta, and it was about a 1/2 quart low. I filled it up, and guess what, the overheat warning light has not come back on since--four days and lots of starts later.

Some things are just not meant to be explained.

Thanks again for your help!
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Tuesday, May 12th, 2009 AT 7:50 PM

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