Mechanics

SPEEDOMETER/TACHOMETER/GAS GAUGE NOT WORKING

1986 Volvo 740

Electrical problem
1986 Volvo 740 4 cyl Two Wheel Drive Automatic 207000 miles

I recently purchased this car that had been sitting in a field for four years. After I got the car home, I went through the normal things prior to starting the car using the key. The engine purrs and sounds great for having over 200K miles and been sitting for four years.

The problem that I have is that the speedo/tach/fuel all indicate in their de-energized positions. The only thing that moves/has moved was the tach. The tach orginally worked, but now does not. Is there something in common with all three or do I need to handle each one separately?

I have pulled the instrument cluster out and performed a visual as well as a physical check with a fluke. I have checked the plugs in the trunk for the fuel gauge as well as the speed plugs. Is there some resistance that I should expect at these connections or does it vary with fuel/speed? Can I use the fluke to give me a reading of speed (relative) if I connect to the sensor? I don't even know where to look for the tach.I would suppose the ignition coil, but there doesn't seems to be any other connections/loose wires, etc.

Any help would be greatly appreciated.
Thanks,
BullNuke
Avatar
Bullnuke
July 6, 2008.




Hi bullnuke,

After sitting for so long and with so many items not functioning at the same time, it is hard to accept that all these itema had failed.

I would suggest checking for electrical power supply and grounding faults.

The tachometer gets its signal from the ignition coil (-) side. It could be bad wire harness connectors that is causing the problem. Connect a wire direct from the ignition coil and test if it works the tachometer.

KHLow2008
Jul 21, 2008.


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