Rallye Gauges Oil pressure sending unit

[oneof52]

Hello,

Need a little help. Recently I had my Rallye gauges rebuilt. Started the car, the oil pressure gauge pegged H and even after I removed the wire, stayed there.

After a while it dropped down below L and has not moved. Diagnosis shows that there is 4.96VC at the wire and while the car is running I see 41 Ohms from the tip of the sending unit.

My guess is that when the gauge pegged, it broke the pointer and dropped. Here is what I have installed;

Melling M63 oil pump, Standard Motor Oil Pressure Gauge Sending Unit.

Q1 - What should the sending unit resistance be while - Off/Idle/Just Started

Q2 - Any suggestions to replacing the sending unit if its not a correct one? Or something that is proven to work?

 

[Katfish]

There's always 5V on 1 side of the gauge, the sending unit provides a variable path to ground. Sounds like the wire to the sending unit might be shorted to ground.

Edit: Reread your post, 41 ohms sound right. All gauges, like fuel basically operate around 10-73 ohms.

 

[oneof52]

Not sure if wire is shorted to ground. I measure 4.96vdc at the wire . I think the needle is broken. The needle is well below L

 

[Challenger RTA]

Check the sending unit also. the sending unit need a little sealer on the treads. But it completes the circuit through the threads.

 

[MAC]

Gauge looks dead to me, replace it with another one

 

[oneof52]

So here is another piece I just received..... the person who installed the cluster told me he connect the 5 vdc output to the opposite post. Would that cause the needle to peg the other way? - It was a freshly rebuilt gauge

 

[Challenger RTA]

Back
check the insulators.

 

[Deathproofcuda]

Use a mutlimeter to check for continuity between the two posts coming out of the back of the gauge. If you have no continuity, then the wire inside the gauge is broken or fried and you will have to replace the internals of the gauge.

 

[oneof52]

Thank you , will do it tomorrow and reply

 

[Deathproofcuda]

So here is another piece I just received..... the person who installed the cluster told me he connect the 5 vdc output to the opposite post. Would that cause the needle to peg the other way? - It was a freshly rebuilt gauge

Maybe I'm wrong, but I don't think there is any difference which direction the current runs through these gauges.

 

[Deathproofcuda]

Go to this link and download Master Technicians Service Conference Reference Book 66-10 "Thermal Electric Gauges" for a great explanation of how these gauges and their sending units work.

Browse MTSC by Model Year – 1966 – MyMopar

 

[moparleo]

64-76 MOPAR RALLYE DASH OIL PRESSURE *GAUGE* SENDER - 340 360 383 426 Hemi 440 | eBay

 

[Katfish]

Standard Products PS59, $21 on Amazon

 

[Deathproofcuda]

64-76 MOPAR RALLYE DASH OIL PRESSURE *GAUGE* SENDER - 340 360 383 426 Hemi 440 | eBay

The mid-range ohms reading that the OP shows in post #3 suggests that his sending unit is probably functioning properly and is not the issue. At that resistance reading the gauge should be pointing to about mid-level.

 

[moparleo]

Just wanted to post what the proper sender looks like. I have seen guys trying to use the light type sender.

 

[Deathproofcuda]

Just wanted to post what the proper sender looks like. I have seen guys trying to use the light type sender.

 

[EW1BH27]

Just wanted to post what the proper sender looks like. I have seen guys trying to use the light type sender.

Same here...

 

[Deathproofcuda]

Thank you , will do it tomorrow and reply

@oneof52
Did you ever get this figured out?

 

[Challenger RTA]

Don't forget about the bulkhead connector.