Oil pressure gauge

[Lbs]

I have a 73 cuda with a rallye dash and I recently bought a new oil pressure gauge for it as the old one was no good. The sending unit is also new as is the wiring harness. I have also put in a new solid state voltage limiter on the cluster. The problem I have come up with is the new gauge just pegs high when you turn the ignition on even if you don't turn the motor over. When you run the motor it stays pegged when it's warmed up and never comes down till you turn the key off. Any ideas would be greatly appreciated.



Thanks, Mike

[anlauto]

No expert here for sure, but could the post of the gauge be grounding on the housing ?

[Lbs]

I am pretty sure I have a good ground. I grounded the dash cluster and the switch cluster to each other and then ran a separate wire up to the battery. All the other gauges seem to work fine. Thanks for the input though, I'm sure somebody must have run into this problem before.

[CudamanTom]

I am pretty sure I have a good ground. I grounded the dash cluster and the switch cluster to each other and then ran a separate wire up to the battery. All the other gauges seem to work fine. Thanks for the input though, I'm sure somebody must have run into this problem before.

I could be wrong but I think Alan was asking if you have shorted the post for the electrical contact to the ground/housing of the gauge. Causing a direct short thereby pegging the gauge as soon as the key is turned on.

[anlauto]

The two posts on the gauge are NOT supposed to ground against the housing, that's why there's a cardboard washer type thing, also if the gauge is slightly off position, the post will contact the housing which it's NOT suppose to do either.

If the gauge is in contact with the housing maybe it would peg on full 

[Lbs]

Ahhhhhhh!!!!!  That is something I haven't checked. I will check for that in the morning and let you know what I find.

Thanks

[anlauto]

I'm just guessing, but it's worth a look 

[purple1]

Are you sure you have a sending unit for the gauge? The one for a light will peg the gauge and never work right.

[734406pk]

I have a 73 cuda with a rallye dash and I recently bought a new oil pressure gauge for it as the old one was no good. The sending unit is also new as is the wiring harness. I have also put in a new solid state voltage limiter on the cluster. The problem I have come up with is the new gauge just pegs high when you turn the ignition on even if you don't turn the motor over. When you run the motor it stays pegged when it's warmed up and never comes down till you turn the key off. Any ideas would be greatly appreciated.



Thanks, Mike

Mike- either your sender terminal or wire is shorted to ground or you have a bad gauge. First check that you have the insulating washers installed on the studs. Then disconnect the sender wire from the gauge. Turn on the key switch. If the gauge still pins full scale w/o the wire connected, your issue is in the gauge and or panel. If it stays on zero, reconnect the sender wire. If you get a full scale reading, the issue is in the sender/wire circuit. Disconnect the wire at the sender and recheck. If still full scales the gauge, you have a short in the sender wire. If it stays on zero with the sender disconnected, the sender is shorted. If nothing works to bring down the full scale reading, it's a defective gauge. Also driving the car with a potential short/full scale reading can damage a new gauge. They have a thermo electric element inside that will burn out. Post back if you have any questions.

[Lbs]

Thank you everybody for the  help. One of the posts was grounding against the case. I don't know if this is normal but the gauge still goes up to 1/4 when you turn key on but don't start the motor and when you start it, it runs at about 3/4 which seems correct.

Thanks again, Mike

[734406pk]

Thank you everybody for the  help. One of the posts was grounding against the case. I don't know if this is normal but the gauge still goes up to 1/4 when you turn key on but don't start the motor and when you start it, it runs at about 3/4 which seems correct.

Thanks again, Mike

Try disconnecting the oil pressure sender and turning the keyswitch on. Does the OPG still go up to 1/4 scale?

[Lbs]

I unplugged it from the sending unit and turned key on and the gauge didn't move. Leaving the key on, I attached it back to the sending unit and the gauge crept up to almost the 1/4 reading. Does it still seem like something is shorting out?       Thanks

[734406pk]

I unplugged it from the sending unit and turned key on and the gauge didn't move. Leaving the key on, I attached it back to the sending unit and the gauge crept up to almost the 1/4 reading. Does it still seem like something is shorting out?       Thanks

This sender is no good. It is out of range for some reason. With the engine shut off and key on, there isn't any oil pressure. Yet the sender is reading 1/4 scale. I would try a new sender. It should read 0 psi with the key on engine off. The good news is your new oil pressure gauge isn't burnt out !

[Lbs]

I will chase that down next. Thank you, and everybody else for your help on this.