89 Econoline Temp & Gas Guage spiking to FULL & HOT

[46fd04]

I have a 1989 Econoline E350 Motorhome with a 460 c.i. motor.

This year, I thought I had an overheating problem, due to the temp guage suddenly going to HOT, then coming back down to 1/2 at intermittent intervals.

I replaced the thermostat, pulled the rad and had it flushed, cleaned & inspected. Put it all back together, and it still does it, intermittently.

Using an infrared digital thermometer, the temp is 200'F at the thermostat housing, 185-195 at the top of the rad, 155 at the lower rad hose, all good from what I've read.

Turns out, now that with the fuel tank is 1/3 full, I see the fuel guage also spiking to FULL when the temp guage spikes to HOT. When I knock on the instrument panel, the guages return to normal.

I read somewhere it might be a grounding issue.

Where do I start?

What part is having the grounding problem, resulting in both guage spiking simultaneously?

Thank you,
Gord from Toronto, Canada.

[CHERYLHUFFMAN]

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[chucksterville]

it is a grounding issue.
pull the dash cluster apart,(trim and blah-blah)
take a Q-tip and some alcohol and clean the plug connections on the gage cluster.
make sure the plugs seat back in good.
pretty simple fix.
same thing happened on my 97 t-bird.
(don't turn the odometer back with a knife-point just because your in there, that would be illigal