M37 fuel gauge wiring

[OutpostM37]

I have a 1963 M37 that I purchased two months back. I also have manuals TM9-8030 and TM9-1840A, engine and clutch.
The vehicle had the standard lighting 3 position switch replaced with a pull type for the lights. Many of the wires are cut under the dash.
I have installed a new gas tank with a M37 correct sending unit. I have removed the SW fuel gauge part number 8376374 505-J which I believe to be the original.
There is no wiring diagram in either of my manuals.
Does anyone have a wiring diagram that can be shared or know the connections on the back of the fuel gauge? +24v to ? case is grounded and the sending unit to ?
I have wires marked 33, 28,27 loose under the dash.
Thanks in advance.

 

[OutpostM37]

Found a PDF for the M37 wiring and needed connections.

 

[Storm 51]

Wire 27 goes from the ignition switch to the fuel gauge in the dash. The spider harness behind the dash is all wire # 27 and is the power for all the dash gauges. Wire # 28 goes from the fuel gauge to the fuel level sending unit on the fuel tank. Wire # 33 goes from the temperature gauge in the dash to the temperature sending unit on the engine.

Hope this helps. I'll try to find the page number in the manual that has the wiring diagram when I get home tonight.

Good Luck!

 

[OutpostM37]

Thank you for your help. Very appreciated!

Wire 27 goes from the ignition switch to the fuel gauge in the dash. The spider harness behind the dash is all wire # 27 and is the power for all the dash gauges. Wire # 28 goes from the fuel gauge to the fuel level sending unit on the fuel tank. Wire # 33 goes from the temperature gauge in the dash to the temperature sending unit on the engine.

Hope this helps. I'll try to find the page number in the manual that has the wiring diagram when I get home tonight.

Good Luck!

 

[Storm 51]

You're welcome!

I hope it helped.

 

[maccus]

The wiring diagram is on page 258 of manual TM 9-8030.

 

[just me]

Make sure the sender is grounded. It won't work with a marginal ground. I ran an extra ground wire to the frame rail from the sender because relying on the the tank straps wasn't good enough.

 

[mdainsd]

You didn't say if your truck got converted to 12V along the way.

In addition to a good ground at the tank sending unit (I run a separate bare braided jumper from the sending unit to the frame, using internal star lock washers), The instrument panel must have a really good ground, otherwise all sorts of gauge weirdness can happen. BTW I added the same braided ground jumper from one of the gauge cases to the body behind the instrument panel.

 

[OutpostM37]

mdainsd:
I have a new braided ground strap from the sending unit to the frame (clean sanded area on frame) as seen in the pic. I will take your advice and add a ground to the gauge case & to the dash. My vehicle is standard 24v powered.

 

[KevinGaus]

Can I get in on this? I’m in the same boat. I have a 28, 27, 33, and a ,0
one must be the low air buzzer. And 3 wires are cut and have no tags.

 

[TruckGuy]

OutpostM37:
What fuel tank are you using? You have it adapted for a original sending unit?

 

[Bill Nutting]

I tried to replace my fuel gauge in my 1953 M37. I bought a new sending unit ( works good), and a new gauge. The new gauge doesn’t work. I reinstalled the old gauge and it works like it did before it died ( old sending unit quit). When the tank is full, it reads 3/4. I was hoping the gauge would read full on a full tank. Here is the question. My old gauge has the Douglas connectors. The new gauge uses the newer rubber connectors ( not sure what they are called). On the new gauge one connector has ribs and one doesn’t. Which one is supposed to connect to 24 volts and which one connects to the sending unit? Second question, does it burn out the gauge if you connect them backwards? When I read the old gauge with an ohm meter it read about 270 ohms. The new meter reads open. I don’t know if I wrecked it or it was bad out of the box. If I burned it up, I don’t want to ask for a refund. If connecting them backwards doesn’t hurt them, I will ask for a replacement.