g741.org

Hi All,

I'm the proud new owner of a '62 M37! Hoping you can point me in the right direction of a mis functioning oil pressure gauge. It is a 24v system. When I start the truck the gauge doesn't read and is all the way to left. If I tap it a bunch of times with the end of a screwdriver it pegs all the way to right. It is a 60 psi gauge. Once pegged to the max, it stays like that until I turn off the truck. I've read some the troubleshooting guides, but not having much luck. Does the symptoms I describe lead you to think it's a particular problem? The truck runs and drives fine. From the perspective of me looking at the front of the gauge panel, I see the left side connection (closest to the steering wheel is a male/female tube type connection. It was taped and when I took off the tape, it slides apart very easy. I don't see a way to crimp it. How do you better secure these? The right side connection has a 4in piece of modern wire from the original wiring to the back of the gauge. Your guidance is much appreciated!

if the "tube" connection is a splice between the wire ends, you can cut the wires into it, and splice in a new butt connection. I am assuming you have a military electrical gage not a mechanical after market one. Try posting a pic of what the back of your gage looks like. The wiring on these old trucks over time cracks and frays, and starts to short out. These trucks have circuit breakers, not fuses. The military wire is 14 gage rubber clad, and ages poorly. I have gradually learned to read a wiring diagram, and now everything on my truck works, even my black out lights. I suspect your truck has had someone "jury rig" electrical things.

These trucks use a partial flow oil filter system, and act about 40 psi and less don't send oil to the filter. Most have a pressure bypass at oil pressure above about 55 psi. Hot oil pressure with 10-40 tends to be around 35 to 40 or so psi on most of our trucks. Use oil with plenty of "zinc" too.

Your truck probably has waterproof rubber Packard connectors, the older trucks, mine a '52, has a mix of the previous metal Douglas connectors. You can buy both, or use modern splices, as the military connectors use a special round crimp tool, although you can solder them too.

To post a pic, I use a free account at PostImage.com, then highlight the link for "hot link for forums', on my MAC then command C, then go back to your post, click URL above, click command V, and it will appear on your preview. there may be other ways to post pics here, too.

If you replace the sender or gage, they have to match, a 60 psi sensor to a 60 psi gage. You are going go need a set of reprints of the TM's for your truck, you can get them from the vendors here. Pretty much everything is available from them.

When I got my own '52", just a bit weathered and needing an engine rebuild, I read just about every forum post gong back years on this forum, and gradually learned a lot. And welcome to a great forum and we are hear to help you as much as we can. Hal Copple

Thanks for the reply. Here is the gauge and backside. The terminal close to the steering wheel slides on and off easily. Is the metal bell housing supposed to slide down and hold it in place? The connection on the right is not tight where the new wire meets the old. It was taped, but when tape is removed it slides apart. What does having no gauge reading until I tap it, then maxing out the gauge after point to a from a diagnostic perspective? Images below. Thanks!

I found a general gauge troubleshooting guide and followed the instructions, leading me to believe the gauge is bad. With ignition on, the needle doesn't move when I connect a wire to where the sending wire would normally come in and take it and and off ground. I bought a new one on ebay so hopefully that is it. What I can't tell is if the gauge was grounding itself correctly. When I tested if it was getting voltage and tapped the gauge bracket to get ground, I always didn't get a connection. I found if I tapped the bracket of another gauge it was more reliable?

Someone has jury rigged your connections, with poor contacts. Could be a source of short and spark in time. If you are going to do a lot of military rewiring of your truck, it might be just best to invest in the right crimper, and a set of metal Douglas or rubber Packard disconnects. The same crimper works on both. You can get the connectors from the vendors or Ebay, but are not cheap. I can try to post a pic of how to use the small parts to properly do both. I bought my circular crimper on Ebay, it has circular teeth that crimp around the metal and wires. When I redid some of my connectors, the metal Douglas ones sometimes pulled the wires out from corrosion. Some diaelectric grease will make them easier, esp the rubber Packard ones, to install and disconnect when necessary.

I will try to find where I bought my crimper, it was new and works just fine. HC, aka NAM VET

Congrats,
Is there a spider harness in there?
I've got a pair of the McCallister crimper' that I am never going to use, I paid too much for them, not sure what they are going for now? I think I also have a spider harness?