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Gas gauge works outside the dash. The two studs are unprotected going through the mounting plate. What keeps them from shorting on the plate? I realize they are all eventually connected, but not by the mounting plate. What am I missing? Thanks, Roger

Sounds like you are missing the fiber washer that insulate the post's. Nylon walkers could also be used.

Roger.
If you look between the 2 poles (on the side that butts up against the mounting plate), there is a copper plate/bridge that connects both poles. Once the gauge is attached to the mounting plate, this bridge should fit firmly against the mounting plate. The 2 poles should have a piece of insulating material that keeps the poles from contacting each other. (I don't remember if the poles were insulated from the mounting plate.)
This copper plate/bridge needs to make good contact with the fuel gauge mounting plate so it grounds. (I was told this by the technician that rebuilds these gauges from the company that sent me this reconditioned 40 fuel gauge.) My gauge would not work because I painted my mounting plates (restored my instrument cluster with new decals and paint) and therefore the copper plate (between the poles) did not ground properly. I removed the paint and that did the trick. I also made sure the instrument cluster made a good ground to the dash. Paint was my biggest problem.
I did bench test with ohm/volt meter and circuit testing light. Be careful when you mess with the gauges. It's about the most uncomfortable and cramped area to work in, even with the seat removed!

When I tested my gauge, my fuel sending unit was out of the tank. I grounded the sending unit and attached the fuel gauge to sending unit wire. I also hooked my ohm meter. With the ignition switch on, I raised the float lever to the empty position, ohms should read around 0, gauge should read empty. Now I moved float lever to full position, ohms should read around 30, fuel gauge full. This was my method of bench testing fuel gauge and sending unit.

My gauge works very well now. I'm thinking the main problem was the paint, but it could've been something else? I hope others chime in to help. I'm just a piano tuner rebuilding a 40 Chevy!

Good luck.
Curt

Yeah, I noticed the brass plate on back. Checked resistance between each post and the plate. Different readings. Tells me current through the two coils goes to ground through the plate. But there is no insulation between either post and the holes through the sheet metal mounting plate. Therefore when nutted down, both posts and the brass plate are all in contact with the mounting plate. To make it even more curious, the holes in the plate are no larger than the posts. No room for insulators. It's all original too. Makes no sense.

I sent my fuel gauge (core) to www.bowtiebits.com
They sent me a refurbished one within about 2 weeks. When I installed the rebuilt one, it did the same thing as my original gauge. It would move below empty when I raised the float level to the full tank position. Bad ground, or probably no ground. I called to speak with the technician and he said to make sure it grounded to the plate. Of course, as stated in the previous post, I had lots of pretty paint to remove!
Bowtiebits.com was helpful and the cost was $65.00 plus shipping.

Maybe someone could post some photos of how the gauge/posts go together with the mounting plate.

Curt

Roger
I took a good photo of how my gauge is attached to the mounting plate. It shows the gray paper insulator positioned between the poles. If you'd like, I can send the photo to you via email. Just send me a private message (pm) with your email address and I'll get the photo to you ASAP. I don't know how to post the photo here.

Curt

Hi Curt,

Here are some pictures for you. Notice the red tag on the short fat terminal. It says that "if the hot wire contacts this terminal it may burn out tank unit."

Good luck, Mike

what keeps the two terminals from shorting when they pass through the mounting holes? Both threads are in contact with the same metal plate in the holes. No?

Mike.
Thanks for posting the photos. Hopefully that will help answer Rogers question about what insulates the poles as they go through the mounting plate. As far as I know, the only insulating material is the gray piece you see that goes on between the mounting plate and the washers. This insulator goes up vertically to keep the 2 poles from shorting against each other. I'm not sure if it matters whether or not the 2 poles make good contact with the plate. They just should not contact each other.

I hope someone with automotive electrical expertise chimes in.

Curt

I guess the best way to explain my question is to say the two separate terminals are not separate if their threads make contact inside the holes through the plate. The paper plate under the nuts has no effect on this situation. I'm mystified.

I know. It is strange. I don't think the circuitry of this works the way we think it should work. The gauge is simply measuring the resistance of the fuel sending unit. I don't think (maybe I'm wrong here?) there's a lot of voltage going through the gauge anyway. (Look at how small the wire is on the coils).

I had a very frustrating time getting my gauge to work as well.
I checked everything from the fuel sending unit, the float position, ohms readings, good ground connections, and even sent my old gauge out for a replacement. The culprit was found to be a bad ground on the back side of the gauge where it mounts to the mounting plate. If you have rust, oil, paint, tape or whatever, that can cause problems. I even removed paint where the fuel gauge mounting plate makes contact with the instrument
cluster housing. Check for loose wiring on your ignition switch and other places. Are you getting power to your gauge? Do you have a good and accurate schematic diagram?
If you don't, I've got a good one I can send you.

When I installed my new gauge, I just pushed the 2 poles through the mounting plate,
Placed the gray insulating shield on next, washers, nuts, electrical connections, washers, then the last nuts. I installed the gauge assembly back to the instrument cluster. Then I installed the instrument cluster assembly back to the dash-making sure all was well grounded. Turned on the ignition switch and finally got it working.

It was a royal pain but I finally was successful. I'm sure you will be too.
Also, there is a good technical topic on this here: https://www.fillingstation.com/articles/fuelgaugetesting.htm

Curt

Hi Rodger,

I hope you can better understand the insulation process by looking closely at two more pictures.





The two threaded brass looking bolts are mounted in a 1/16" pad of insulation. You can see in the last picture of my previous post that the insulation material is a shade of burgundy. Because of how the bolts are sandwiched into the insulation and the brass colored plating on both sides of the insulation both bolts are indeed insulated from touching each other.

Good luck, Mike

P.S. Hopefully, someone with electronic experience will add to this explain?