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Hay folks,
New member and looking forward to a little help on my on going project. I have a M37 1951 rig and realy like it. Runs great, starts easy, and sounds strong with no smoke. Here is the deal, all the old wiring was shot and most had been removed, I can't aford a new harness right now (wife shock) so I have been adding the nessasary stuff as I get things going. Now I am trying to get the gauges going and have been sucessful with the Amp meter, and temp guage. When I tried the oil gauge the needle hardly moved about 10 lbs on the 120lb meter, I know this is not correct oil pressure. The engine sounds to good for this to be true. I only had one bakalight conector and one 96ohm resistor to try the guages with. Some nut had just ripped the old ones off and all were broke but the one. Anyway here is my question, does the oil guage need the 96ohm resistor like the Temp or does it get a fuse? Looking in Vintage parts I see a 120 gauge that they talk about a fuse with. HELP
Confused,
Tim

tstephenson wrote:Hay folks,
New member and looking forward to a little help on my on going project. I have a M37 1951 rig and realy like it. Runs great, starts easy, and sounds strong with no smoke. Here is the deal, all the old wiring was shot and most had been removed, I can't aford a new harness right now (wife shock) so I have been adding the nessasary stuff as I get things going. Now I am trying to get the gauges going and have been sucessful with the Amp meter, and temp guage. When I tried the oil gauge the needle hardly moved about 10 lbs on the 120lb meter, I know this is not correct oil pressure. The engine sounds to good for this to be true. I only had one bakalight conector and one 96ohm resistor to try the guages with. Some nut had just ripped the old ones off and all were broke but the one. Anyway here is my question, does the oil guage need the 96ohm resistor like the Temp or does it get a fuse? Looking in Vintage parts I see a 120 gauge that they talk about a fuse with. HELP
Confused,
Tim

You have the incorrect gauge. It should be a 60lb max. The 120lb is used on the larger diesel powered trucks. Each has its own compatible sending unit. You can use the 120 gauge with the correct sending unit & get an accurate read out. Most likely what you have going on is someone has installed a 120 gauge & left the 60 sending unit in place thus the incorrect read out. What I would do is obtain a 60PSI gauge & see if that doesn't take care of the issue. Military standard gauges operating in the standard 24 volt system do not require resistors or fuses, only the gauge & proper sending unit.

does anyone know how to tell what sending unit I have, is there a test with a volt/ohm meter I could do? on the sending unit? I think it is very possible the guages were not original in this truck, the panel had gray primer on it found no where else on the truck.

Hey, I just looked at a m37 with gas 230 engine on e-bay and in one of the pictures you can see a 120lb oil guage, what is the deal? Still confused, is anyone else or am I alone out here in the mud

Don't believe everything you see on eBay. About the only thing eBay is good for is to gage "fair market value" or what someone will pay for it though I don't always agree with that either. People may say something is correct. When I spot something that doesn't look right or I know is wrong, I figure they just didn't know better (didn't do their research) or they are just trying to sell it and don't care.

My truck has the original oil press gauge and it is 60lb. I can't get to my sender right now to look at it for markings but I would say that since we know your gauge isn't the right one, I'd replace the gauge anyway; they are relatively inexpensive, easier to get at and replace than the sending unit. Sounds like that might be your problem and the sender is still original.

tstephenson wrote:Hey, I just looked at a m37 with gas 230 engine on e-bay and in one of the pictures you can see a 120lb oil guage, what is the deal? Still confused, is anyone else or am I alone out here in the mud

The 120 gauges are easier to come by these days since the military no longer uses the 60 in current vehicles. That's why you see some that have been replaced using the 120. It works great if you change out the gauge & sender, otherwise you get a false reading. I would also replace the gauge first with a correct one, might cure your problem.

thanks guys, I will try the 60lb deal and see if it works out. I will post the results when I am able to make the swap