Temp gauge 47 Merc.

Displayman

Displayman

Senior Member
I converted our 47 Merc. from 6volt to 12 volt recently. Stock flathead v8,
Had the amp gauge converted to voltmeter. During the conversion
of voltmeter gauges all were supposedly tested. All worked during test.
I installed in car with a 12v to 6 v relay for gauges. All gauges work
except temp gauge. Needle starts off in hot and never moves.
Drove car in 95 plus degrees and car boils over a little when parked.
Temp gauge never moves. I even tried attaching wire from thermostat to other side of gauge, still always parked in hot according to gauge.
How do you test for bad gauge? I replaced the wire between the 2 thermostats, and all wires in car are brand new Ron Francis wiring.
Bad thermostats? Bad gauge?
Looking for any suggestions.

Thanks,
Bob-Hampshire, Illinois
 
Jim,
I did everything in your print, and there is still no movement in the gauge.
Any other suggestions would be appreciated.
Thanks,
Bob - Hampshire, Illinois
 
Ground the wire from the temp gauge to the sender. If the gauge needle does not move towards cold, either your gauge is defective or you do not have 6 volts to the gauge.
 
Update, I grounded wire from sender, needle did not move.
Gauge has 6 volts used a hotwire test wire with light.
Must be bad gauge. I noticed all the gauges I have seen for sale, ALL
have the needle showing hot is that normal?

Thanks,
Bob- Hampshire, Illinois
 
One thing to try before you replace the dash gauge is to jumper the two wires together on the 2-pole sender and see if it works. Temp gauges always rest at the HOT position when the key is off and increaded current pulls it to COLD when key is turned on.

Jim
 
Displayman said:
Update, I grounded wire from sender, needle did not move.
Gauge has 6 volts used a hotwire test wire with light.
Must be bad gauge. I noticed all the gauges I have seen for sale, ALL
have the needle showing hot is that normal?

Thanks,
Bob- Hampshire, Illinois
Click to expand...

Yes the needle always starts at hot, when you start the car it moves over to cold. Sounds like your gauge is probably bad though.
 
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