Suspect Temp Gauge of not working but need to test

Tiny
JJ69FURY
  • MEMBER
  • 1969 PLYMOUTH FURY
  • 90,000 MILES
69 Plymouth Fury Convertible with non stock 383 2 barrel. Temp Gauge reads high but not sure gauge is working. Need to know how many ohms should cause the gauge to read in the Middle and how many should cause it to read high? Anyone know? Have done ALL the regular stuff to treat overheating (thermostat replaced, temp sensor replaced, new hoses, new radiator, new radiator cap) Testing for head gasket and water pump. Only two things left I can think of except if the actual gauge is bad.

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Friday, May 10th, 2013 AT 10:33 AM

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Tiny
HMAC300
  • EXPERT
I don't remember the ohms for that but an easy way to test is turn the key on and ground out sending unit cable to engine block. If the gauge moves to hot then it may be the sending unit even though it was replaced. On those the gauge ran above the middle on the line or does it go all the way to H? If the engine has been modified your radiator may not be large enough for one thing eve though it was replaced. Also you can put a water pump off of an a/c car on it as they had different impellers. And use the radiator cool down stuff it works. One other thing is to check to see if lower hose is sucking together when it's revved because some of those had a reinforcing wire in the hose to stop that kind of stuff or get a hose that isn't fitted as those have that.
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Friday, May 10th, 2013 AT 12:20 PM
Tiny
JJ69FURY
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Hi hmac300
Did the test with the key turned and grounding the sending unit cable to the engine block and the gauge went to C not H. I am getting pretty certain it is either the sending unit or the gauge because we wired an old themometer to the top radiator hose and put one in the radiator top and they do not get above 180 degrees. The gauge however is buried at H.
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Friday, May 10th, 2013 AT 12:42 PM
Tiny
JJ69FURY
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Any idea how I might find out what the OHMs are supposed to be for the temp gauge? I am worried that I would need to replace the entire instrument bundle to fix.
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Friday, May 10th, 2013 AT 12:43 PM
Tiny
HMAC300
  • EXPERT
Your gauge is bad or make sure the sending unit has blinking light with a test light if that has a blinking light then i'd say it's a gauge but I don't remember if those have a circuit board or not. If it is direct wired try switching your wires in the back as they may be backwards. It is definitely not the sending unit. Are these factory gauges or a aftermarket, if they are then i'd say wiring is backwards. I dont' remember and I've been doing this for 50 yrs if there are wires going to gauge try switching them and see if it works then. I don't remember if it had a flimsy circuit thing or not.
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Friday, May 10th, 2013 AT 12:56 PM

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