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Discussion Starter #1
My 65 fastback has just started doing this. When started, the needles on the gas and temp gage read correctly but when I stop or take a corner, the needles go all the way to the full or hot temp. Any idea on why this would happen?

Thanks
 

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How about the oil pressure gauge? If they all go high its likely your constant voltage regulator is no longer very constant but is going bad.
 

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Ivy- if none of the gauges work can you eliminate the constant voltage regulator and maybe look for a ground problem?
 

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Likely the regulator as Ivy suggested. I'm assuming you have the standard '65 instrumentation (no oil pressure gauge).
 

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Joe,

Yes, I missed that it was a '65 so unless its a GT it would not have an oil pressure gauge.

vsop,

A ground problem is always possible but there are two potential ground problems. The individual gauges get their ground at the senders so if it were a problem there the needles would drift lower instead of higher. A ground problem at the CVR could cause it to quit cycling and if that is the case then the needles for all the gauges would drift high.

Since it affects more than one gauge it would seem to be a CVR problem whether that be a ground or just general failure.
 

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If it's the instrument panel voltage regulator get a solid state unit from somewhere like CJ Pony parts they run around $55.00 The cheapo units apparently can die within minutes of installation.
 

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"but when I stop or take a corner"


If either of the wires going from the regulator to the sending units go to ground, it will make that gauge read high. I would look under the dash at the wiring harness and see if it may be rubbing on something that has worn through the insulation. Look for anything that may be rubbing on any linkage, or can be moving when you turn. I'm guessing after the wiring goes through the firewall, they would separate to different routing so I would start under the dash first.
 

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It could still be the regulator, even though it seems effected by the car's motion. Remember that the original units are electro-mechanical, so they actually contain a moving contact that could be influenced by applied G-forces. Unlikely, maybe, but definitely possible. I would also verify that the regulator body has a good chassis ground. There are only three wires, 12v in and two 5v out, so there is no external ground wire.
 

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Always disconnect the battery ground cable when removing or installing the instrument cluster. If I remember right there is one screw on the instrument cluster that grounds the instrument cluster to the dash, this I may be wrong on, if you are troubleshooting the instrument cluster with it exposed you will have to put a temporary ground on it to the dash. I would check the grounds, like the one on the back of the passenger side cylinder head to firewall, the ground on the instrument cluster to dash and the constant voltage regulator (instruments), you could run a ground wire from the instrument cluster to the dash. And the last thing I can think of, is there might be like a small particle floating around in the constant voltage regulator (which means it is bad also) that is rolling around when driving. Good Luck.
 

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Discussion Starter #10
I have a separate after market oil pressure gaurg and it is fine. I only have an oil light on this car as it is a September 64 build date.
 

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Discussion Starter #11
thanks for the info Joe - It may be the CVR - as the gas and thermostat are the gauges that float to the full and hot side. Although it immediately goes right back to the normal reading. Since I do not drive the car that much, I do not think that anything is a grounding issue and I have checked under and do not see anything unusual. I will do some more of "watching" of te gauges as it seems very random right now. Thanks to all of you with your feedback. I really appreciate it and can always know to come back to this forum for some great input.
 

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Discussion Starter #12
One more item that may help - I have also checked the gauges reading when I turn the key of the car just into the start position. The gauges read correctly.
 
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