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1952 M-38 24 volt. Recent acquisition. Installed new matching oil pressure gauge and sending unit from Peter DB. Previous owner had installed some ugly gauges that I wanted to replace.
Seems like it should be straightforward. Sending unit-to-correct wire- to-Oil pressure gauge. I read about the grounding issue with gauges/dashboard, so I made a small harness, similar to the #27 spider one, grounding it to all four gauges, then to a ground on my firewall. When I turn the ignition to the on position, the needle swings over to the max (60) reading on the OPG.
I would have thought that the gauge would not read anything unless the engine was running. I have not started the engine yet, just turned it over a couple of times, because I am waiting to feel certain that all gauges, especially the OPG are operating correctly.
As I write this, I am wondering if 1-I should not have grounded the gauge, or 2-, if my grounding "spider-harness" is connected to the ground on another one of the gauges, and connecting to something other than a ground.
Thanks

Where on the gage did you connect this added ground wire?

Check your wire from the sending unit to the gauge.

I was getting no reading when connected normally, put a mechanical gauge in as a safety to make sure I got pressure, and the regular 24v oil pressure gauge now pegs when the ignition is turned on.

Not saying this is the absolute problem, but same symptom I have with sender disconnected.

I am waiting for funds to change both sender and gauge to 120 lb which is what the book calls for for the M-38A1. I currently have 60 lb...

Thanks, Wes, for your quick reply. Sorry for my lengthy delay. I just got back from a no-internet location.

The issue seems to be the connection between the oil pressure sending unit and the wire connected to it. It is fixed, at least for now.

This aftermarket oil pressure sending unit has a very (almost too) short pin.
So far it seems to me that one of the downsides of most of the aftermarket gages , seem to be a little wider then they should be.

Because of this, I have decided not to strap on my scuba tank and drive around submerged.

As always, thanks for your help and dedication.

Best,
A