gas gauge problem
 

I'm having a problem with a 1962 Bonneville gas gauge. It will not go quite all the way to empty. I just bought the car so I don't know much about it. I don't know at what point the car actually runs out of gas. I do know that when the tank is empty the gauge reads about an 1/8 inch over full. The previous owner replaced the tank sending unit with a reproduction. Not knowing this I bought another one and since I had it I replaced it again. No difference. I have since tried 3 different used dash units. All read the same. I can see them all possibly being bad but it seems they would not all be bad the same. I check to see if the gauge was getting full voltage (yes). I checked the resistance in the wire going to the tank (ok). I ran a new ground from the tank unit to a nice clean spot in trunk (no difference). I ran a ground to the instrument cluster (no different). I can buy a NOS dash gauge but it is a lot of money and I hate to buy it only to find it didn't fix the problem. When I disconnect the sending unit from the dash the gauge goes to full. When I ground the wire the gauge goes to 1/8 above empty. Can anyone help?

CORRECTION TO ABOVE
 

Correction: It is supposed to say THE GAUGE READS AN 1/8 OVER EMPTY when the tank is EMPTY. Sorry

If you want I can probably repair your dash gauge. You are right on the sender wire, full body ground at that wire should cause the gauge to go to E.


You would have to take your gauge out of the cluster and send it to me.

Check the back of the metal dash housing first, the little silver access panel at the rear of the fuel gauge should be grounded.

One wire is 12 volts + (key on) and the other wire runs from the back of the gauge thru the body wire harness (via several plug-ins) all the way rearward & underneath the car to the tank sender. And then there is a black ground wire from the sender attached to the underside of the trunk floor via a sheet metal screw-bolt and a star washer.

I checked the brown wire all the way to the rear with an ohmmeter and there is less than 1 ohm resistance. I also replaced the ground wire and moved it from the rusty trunk floor to the upper side of the trunk. Do you think the problem is in all 3 of the dash gauges? If so how much do you charge?

Clear The Air
 

Did you use a new/seperate ground wire, directly to the back of the gauge, when you tried to force empty? That would be directly to the sender terminal on the gauge.

Dirty or tarnished terminals can skew readings on 30 ohm gauges. They're a lot more sensitive to resistance than later 90 ohm gauges.

Clay

There is a inherent defect in those older zero to 31 ohms (range span) gauges. The design of those type gauges dates to the mid-1950s. And I second the info in post #5, the older gauges are very temperamental to even a slight ohms change, say in a corroded or tarnished rear cover plate. The rear steel plate on the back is the ground pathway from the 2 coils inside to our car's body ground. Very often that plate gets a "film," tarnish or corrosion on it that interferes with the ground pathway.

After about 15 or 18 years of use those old zero to 31 ohms gauges seem to loose their torque. That; or like yours they go out of calibration.

It's difficult to quote a price for repair unless I have the gauge in front of me. I need to see it and inspect it in-person. It might be $75 it could be $95., It all depends on what it needs.

The other thing is, those old gauges are very, VERY fragile. Once removed from the protected area in the dash cluster they have almost NO support to the dial plate or the moving pointer. So those are difficult to pack & ship without getting bent and/or damaged. (The pointer on that gauge is made from a thin piece of aluminum just a shade thicker than a sheet of paper.)

You say you have 3 used fuel gauges there and none of them are testing as good? Are you sure you are testing them properly?


In 1965 for the Pontiac A body cars they completely re-designed the gauges & those are much more reliable.

FYI: The new and improved gauges have an ohms range span from zero to 90 ohms.

I have had some luck in fixing the older (0-31) ohm gauges, sometimes I can't get one of those to work but I have extra parts here. Plus I am doing this on a workbench not underneath the dash. I built a resistance test box dedicated to the gauges I work on. And I keep a fully charged optima yellow top 12 volt DC battery underneath the bench with fused + and "-" leads running up top.

I have tested the dash gauges by:
1) leaving the gauge in the dash and grounding the BROWN wire at the rear of the car.
2)leaving the gauge in the dash, plugging in just the YELLOW wire at the gauge and grounding the other terminal of the gauge.
3) removing the gauge, applying 12volts to one terminal, grounding both the other terminal and the ground strip at the base of the gauge itself that looks like solder or lead.
All 3 gauges still did not go quite all the way to EMPTY. What gets me is the fact they all read the same.
If I were to send you the gauge what would the turnaround time be?

It seems the sender in the tank might just need the arm bent some to accommodate the correct level if you have issues with more than one gauge. I had the with a 55 Chevy as well as a Fiat Spider.

Time for repair could be anywhere from one to 3 days here, plus time in shipping.

Please PM me your info and I will get it to you. How do I pay you? I have PayPal if you do. Any hints on packing? Thanks.

Best way to pack and ship an fragile gauge or gauge part.
 

Paypal is fine with me. Here is a new tachometer meter that I had made for a 1970-2 Trans Am.

They put these in a brand new plastic container with a heavy-duty thread-on lid.

The meter is bolted into the lid from underneath using at least 2 if not 3, #6-32 machine screws with flat washers. (They punched some holes in the lid first) & so the very fragile parts of the meter are suspended in a layer of air.

My thanks to Peter. I would recommend his services to anyone. Thanks.