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Electrical issue, with dancing fuel gauge!

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bugedd

bugedd

Jedi Knight
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So I take my car out for a drive today, nice cool morning cruise, and I noticed my fuel gauge is dancing and spiking all over the place. It was recently rebuilt by Palo Alto Speedo, so I assume its fine. At the same time I notice the ignition light is staying on. Now if I recall, that light is on when the ignition is turned on, then supposed to turn off when the car starts. It would make sense then that something is going on, maybe with the regulation of electricity, to make the fuel gauge spike. Also, I think the fuel gauge did it with the motor off, key on.
Any thoughts on what might be the issue?
Thanks in advance
 
Your profile doesn't way which year car this is. However, your description of a dancing fuel gauge implies that this is an early 1960s car before the voltage stabilizer and later-type gauges were fitted.

The early gauges basically work using controlled (and somewhat opposing) magnetic fields inside the gauge. While these gauges are not particularly voltage sensitive, the gauge itself must have a very, very good ground and the sending unit must be in good shape if the gauge is to be at all "stable". They are also very sensitive to "sloshing" gas.

I assume that your car is still outfitted with a generator and control box. I would focus your attention first on the charging system and then work on the fuel gauge which is probably an unrelated issue.
 
Sorry, its is a 60 Bugeye.
The sending unit is, from what the previous owner told me, new. After the gauge was rebuilt, it worked fine, fluxuating a bit from the fuel sloshing. But the spiking and erratic behavior is new and seemed to happen when the generator light decided to stay on.
 
Ihat really sounds like your sending unit has a bit of corrosion on the windings, a very common problem. When the car is used regularly the wiper is constantly moving and wiping the rust off of the coils but when a car sits for a long time the rust starts to build up and gives you that jumping needle problem.
The only solutions to the problem are:
1/ drive the car more to keep the contacts self-cleaning
2/ replace the sender and be very sure that the cover is properly sealed to keep moisture out of the sender.

#1 is far easier and more fun. As you drive the car it will jump less and less as the wipers clean the windings.

The red light on indicates that the generator is not working properly- make sure that both wires are connected to the generator and that neither wire is broken under the rubber covering (has happened). If everything is fine there then check that all of the wires are connected at the voltage regulator- if they are all connected then disconnect the battery and one-by-one loosen the screws on the voltage regulator 1/2 turn and re-tighten them (ONE-BY-ONE). This may cure the problem.
BillM
 
Is it a full tank when it does this? You could have a little bit of play in the sender and at a slam full tank this play kind of allows the sender to twist a bit to the side and move the wiper off the resistor coil. This would only happen at a full up tank and would go away after a little fuel is burned off. Some of those new senders are not good quality.
 
No, its at half tank now. I will check to make sure the ground is good and tight on the gauge, then maybe have my voltmeter on the hot to see if there is some voltage spikes.
As for the regulator, I need to learn what all that does. Time to study the wiring diagram :smile: But how would I check to see if the generator is crapping out?
As for the red light for the ignition, that raised a question. Can those little red and blue jewels for the lights be had anywhere? Mine are long gone, and I would like to have that finishing touch on the gauges.
 
Got to find someone who is parting out a Spridget. I found the solution to making the Blue Bluer and the Red Redder was some blue and red vinyl plastic binder page covers. Took a hole punch and punched out several blue and red dots and pushed them into the bezel. Color restored.
 
Never would have thought of that, nice idea!
 
If you were Souix, you would be called, "Dances with fuel gauge".
 
LOL! I have been called worse!
I just took the car out for a spin, fueled up, and the gauge is working normal now. So must be something strange with the sending unit.

Now, as for the ignition light always on. I checked all screws at the regulator, and they all are snug. I was trying to read the wiring schematic, and it didn't help. I take it that if the light is always on, the generator isn't charging enough. Is that a correct assumption?
 
With a generator/regulator setup it could be either or both causing the problem. The generator could be failing to put out enough voltage, and/or the circuits in the regulator could be failing to "cut" the generator in. Test both.
 
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