Topic: WATER TEMP GAUGE
in Forum: C3 Cooling and Heating Systems
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Canada
Joined: 3/9/2008
Posts: 164
Vette(s): 70 VETTE 350/300HP, AUTOMATIC, ALL STOCK EXCEPT FOR MILD CAM,LAGUNA GREY, 3:55 POSI GEARS
WHEN THE CAR IS IDLING IT PRETTY MUCH DOES NOT MOVE, WHEN DRIVING THE NEEDLE JUMPS SEEMS TO STOP AND THE STARTS JUMPING, COULD IT BE LOOSE AT THE CONNECTION OF SENDING UNIT.
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Could be a loose wire, or a bad sending unit. If the other gauges are stable, the connections in the dash are probably okay, look under the hood. The temp sensor is on the right side between the rear two spark plugs. There is one wire connection, and the sensor grounds through the block.
The wire is in fact a ground circuit. The gauge will move to one side with the wire unhooked, and the opposite way when it is grounded. Putting a test light or resistor between the wire and ground, the guage should read steady. The reading will vary depending on the resistance used.
Former Member
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Canada
Joined: 3/9/2008
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Vette(s): 70 VETTE 350/300HP, AUTOMATIC, ALL STOCK EXCEPT FOR MILD CAM,LAGUNA GREY, 3:55 POSI GEARS
I CHECKED THE WIRES AND SEEM FINE, I JUST GOT MY SYSTEM FLUSHED AND THATS WHEN IT STARTED HAPPENING. IS IT DIFFICULT TO REPLACE THE SENDING UNIT, DO I NEED TO DRAIN THE SYSTEM.
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The system will drain itself when you remove the sender! 
Sorry, I couldn't let that one go!
You'll need to drain the radiator, at the very least to remove the sender, and not make a big mess.
If you un-plug the sender, does the gauge still act goofy, or does it stay in one spot?
Another thing it could be is the system is not full of coolant, and there are air pockets in it. The sensor won't read correctly unless it is in contact with the coolant, so if the coolant level is low, it could cause the gauge to fluctuate like that. I only mention this because you say it just started after a flush....
Sorry, I couldn't let that one go!
You'll need to drain the radiator, at the very least to remove the sender, and not make a big mess.
If you un-plug the sender, does the gauge still act goofy, or does it stay in one spot?
Another thing it could be is the system is not full of coolant, and there are air pockets in it. The sensor won't read correctly unless it is in contact with the coolant, so if the coolant level is low, it could cause the gauge to fluctuate like that. I only mention this because you say it just started after a flush....
Joel Adams
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Joel is right (as usual). If they didn't block fill from under the thermostat, then there could well be an air bubble. Happened to me and we had to pull the neck and t-stat and fill from there.
I'd highly recommend waiting until it is cool to try it (don't ask).
I'd highly recommend waiting until it is cool to try it (don't ask).
Former Member
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Canada
Joined: 3/9/2008
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Vette(s): 70 VETTE 350/300HP, AUTOMATIC, ALL STOCK EXCEPT FOR MILD CAM,LAGUNA GREY, 3:55 POSI GEARS
Checked wire at sending unit, removed and put back on, started car seems to work fine. Thanks for the help.
in Forum: C3 Cooling and Heating Systems
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