62 Sprite Fuel Gauge always on Full -

[livinginthepast]

How do I determine whether it's the sending unit, ground/short or guage? Any tricks? Anything I'm missing?

Thanks!

BillW

 

[dklawson]

On the early gauges (before the voltage stabilizer was added) it is imperative that the gauge itself have a good ground connection. <span style="text-decoration: line-through">If the gauge looses its ground it will read full. </span>Start by running a dedicated ground wire for the gauge to see if that restores normal operation.
EDIT: The gauge will not work if it is missing its ground.

The next thing that will make the early gauge read full is if the green/black wire is disconnected (at the sending unit or at the gauge) OR if the sending unit has lost its earth connection.

Several years ago I wrote a letter to a guy in the U.K. who was working with the early gauges. I saved that letter in PDF format for reference. There may be some information in the PDF that will help you troubleshoot this problem:
https://home.mindspring.com/~purlawson/files/OldFuelGauge.pdf
You may also want to Google for "MGA Guru" and visit Barney Gaylord's web site. He has a section devoted to troubleshooting, testing, and calibrating the early gauges.

 

[Bayless]

mostly except if the gauge ground is missing or bad, I think the gauge will read empty. Probably the green/black or the sender itself. You can also check by grounding the "T" post on the gauge. That should make it read empty. If so then ground the green/black at the sender which should also read empty. If so then the sender is suspect.

 

[jvandyke]

My '63 will read full when the tank gets near empty. I don't know why but it otherwise seems fine. I view it as a low gas warning, when it's pegged at F and I know it ain't.

 

[dklawson]

mostly except if the gauge ground is missing or bad, I think the gauge will read empty.

I believe you are correct and I will edit my previous post accordingly. Thanks for catching that!

 

[dklawson]

My '63 will read full when the tank gets near empty. I don't know why but it otherwise seems fine. I view it as a low gas warning, when it's pegged at F and I know it ain't.

The gauge suddenly going to "full" when the tank is really near empty is an indication that the resistance windings in the sending unit have a break in them. The gauge will read normally until the wiper on the sending arm passes by the break. At that point the sender has effectively stopped working (by loosing its ground path). It's just like you unplugged the green/black wire.

 

[jvandyke]

My '63 will read full when the tank gets near empty. I don't know why but it otherwise seems fine. I view it as a low gas warning, when it's pegged at F and I know it ain't.

The gauge suddenly going to "full" when the tank is really near empty is an indication that the resistance windings in the sending unit have a break in them. The gauge will read normally until the wiper on the sending arm passes by the break. At that point the sender has effectively stopped working (by loosing its ground path). It's just like you unplugged the green/black wire.

Well I'm glad it happens right near E where it doesn't bother me.

 

[regularman]

Either you lost the connection at the sender going to the gauge or a ground at the sender. Either of these would cause the gauge to peg full. Any resistance above 70ohms to ground will make it peg full.

 

[HAN8L1965]

Some of you guys have all the luck, how do you get a gas tank that is always full???

Mark

 

[livinginthepast]

Thank you everyone.

This car sold and the fuel gauge when south the night before the truck came to pick up the car.

The buyers are new to LBCs and I felt terrible about an issue surfacing on the the night before the car was shipped. I passed on all of the advice and told them about this forum should they need any assistance. Luckily, it sounds like an easy fix.

Thanks again all!

BillW