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More questions on my 986, gauges not working


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My new to me 986 is having problems with some of the gauges not functioning.  The fuel and coolant temp are not working.  Both are on the same side of the dash cluster.  I'm guessing that it is likely a grounding problem but don't know for sure.  Any suggestions on where to start would be appreciated.  The volts and oil pressure seem to be working.

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Have you checked the wires going up along the engine for the coolant temp?  maybe got hot and melted or broke off.  The fuel gauges can be problematic with age and not read, need to find wires by tank and ground them out and watch for gauge reaction

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Test each gauges sender separately and see if there's movement very simple to do

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GO back to the right rear top corner of the main tank and ground the sender wire stud (centered under the cover).  The gauge should either display full or half full, depending on if you have the auxiliary tank.  (At least this is to my best memory - please somebody correct this if I'm wrong).    Ground the aux tank sender too if in doubt.

The way that circuit works is keyed 12V to the gauge, wire to the tank sender, which provides a varying resistance to ground.   Grounding the sender pin sends the gauge full over.    SO you can only really have a few problems

  • No 12V to the gauge
  • Wire broken or poor connection to the tank sender
  • bad tank sender
  • A bad gauge (very rare)

Its almost always a bad connection or bad sender.

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5 hours ago, Jeff-C-IL said:

GO back to the right rear top corner of the main tank and ground the sender wire stud (centered under the cover).  The gauge should either display full or half full, depending on if you have the auxiliary tank.  (At least this is to my best memory - please somebody correct this if I'm wrong).    Ground the aux tank sender too if in doubt.

The way that circuit works is keyed 12V to the gauge, wire to the tank sender, which provides a varying resistance to ground.   Grounding the sender pin sends the gauge full over.    SO you can only really have a few problems

  • No 12V to the gauge
  • Wire broken or poor connection to the tank sender
  • bad tank sender
  • A bad gauge (very rare)

Its almost always a bad connection or bad sender.

Thank you.  I wasn't sure how to troubleshoot this.  I was looking at a wiring diagram and it appeared to me that both these gauges received power in parallel from the same source.  I was initially thinking a grounding problem but could be power.  I'll do some poking around with my multimeter tonight.

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