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electrical problems

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healeyboz

healeyboz

Jedi Knight
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So apparently I have some sort of electrical issue. Nisonger got my gauge back today and said that it is an issue on my end. I fried the gauge. He said that it has to be a ground issue or an issue with the repop sending unit. I can't see how it could possibly be an issue with the sending unit. Either it works or it doesn't! How could a sending unit fry a gauge? It worked just fine and when I started the motor to let her run for a bit, the gauge went to full and then to empty. I imagine that when it went to empty it was fried. I went out tonight take some readings and when I turned off the ignition, the motor lurched. What in the world???!!! Looks like I need to start chasing wires. Am I getting a spike in the fuel gauge that is causing it to burn up? The only thing I can think of for the lurching issue is a bad solenoid. Dunno....
 
Hey here is a couple links that might help:

Fuel gauge function
https://mgaguru.com/mgtech/electric/fg_01.htm

Fuel gauge calibration
https://mgaguru.com/mgtech/electric/fg_06.htm

Fuel gauge troubleshooting
https://mgaguru.com/mgtech/electric/fg104.htm

Fuel gauge wiring notes
https://mgaguru.com/mgtech/electric/circ_f1b.htm

I just recently went though the gas gauge on my Midget not working, turned out to be the sending unit coil wire on the inside of the housing was broken. A little solder and a quick reassembly and she works perfectly.

Quick check on the sending unit, use a multimeter and check for continuity between the Spade connection and the body. If no continuity the sending unit could have a broken wire, like mine.

Hope this helps you.
Ɛan
 
Are you sure you didn't interchange the B and T terminals? (See the MGA Guru pages in Dan's posting.) This could conceivably blow the coil that normally is in parallel with the sender.

You should be able to measure 12V on one wire that connects to the gauge, and measure something like 0 to 100 ohms resistance to ground, and no voltage, on the other. The Sprite sending unit and gauges do not have the same resistances as the MGA. I forget what they are, but they're not wildly different; you should see something in the 0 to 100 ohm (or so) range. If you measure the sending unit and get an open circuit, something is definitely wrong with the unit or the wiring to it.
 
We measured the sending unit and see that it is working okay. Could it be a wire that has bypassed the regulator somehow that is causing the gauge to spike?
 
Just out of curiosoty have you checked the voltage at the gauge itself? If it is erratic it could be the voltage regulator.
Just a thought
Ɛan
 
A ground issue? Empty is ground. There would be no difference with being on empty which the sender reads 0 ohms to ground (it essentially is ground) and having a sender wire lead that got shorted to ground. Either way should not burn up the gauge. 70 ohms to ground is full, 0 ohms to ground is empty. I don't see how you could "fry a gauge" that was in good working order unless you hooked up a higher voltage than 12 to it.
 
I agree 100% Kim. What are possible culprits for this to happen? Doesn't the issue have to be in the gauge itself or at least the wiring at the gauge? The gauge is off when the ignition is off. Just trying to think what I could possibly have crossed.

Any ideas as to why the starter was bumped when I turned off the ignition?
 
The starter thing sounds like an iggy switch issue.

Just a thought: Could you have a mis-match between gauge and voltage? What I mean is, ISTR Bugeyes don't have a regulator, so if you have a gauge from a later car needing 10V regulated and it gets 12v system voltage, that may cause the internal coil(s) of the gauge to fry?
 
BE guage is PN 2A9089.
 
That is the part number from the orginal factory Bugeye parts list. As everything else has the number on it I assume the guage does as well. Hmmm.
 
Top center of guage dial says FG2530/31 on all three I have.
 
A bugeye fuel gauge is marked on the dial FG2530/31.
A Mk-II fuel gauge is FG2530/64 or /63 it will work with a bugeye sending unit.

A bugeye or Mk-II fuel gauge will only work with a bugeye sending unit. Later sending units work the opposite (OHMs wise) than the bugeye sending unit.

If the "B" & "T" terminal wires are reversed it will cause the fuel gauge to read full when the ignition is turned on and will not read anything but full.
 
Okay,
It is the correct gauge.
He said that it has to be either one of three things. The sending unit is not working smoothly and spiking through a ground. He said that he would be willing to bet that this is the issue. He has seen it too many times to not be this.... or maybe and he said maybe it could be the ground to the back of the gauge. Or it could be the b terminal wire spiking current. His suggestion was to find an original be sending unit and test it or have it rebuilt by them. run an isolated wire from the sending unit to the gauge and eliminate the wiring harness. Ground the sending unit with a wire. Check the ground to the back of the gauge. And make sure that the b wire is not surging...

What in the world???????????????
 
if the b and t terminals are reversed it will burn up the gauge. It doesn't matter what ground it is. The gauge has to be hooked up the same way with both neg ground an pos ground.
 
Okay,
So I got home today and hooked the volt meter up to the ground and B wire that goes to the gauge. It reads 12v when ignition is on. 12v at idle and 14.3 volts when I rev up the engine. I turned on the rear lights and they get brighter when I rev up the engine as well. I am thinking that I either have something crossed or the voltage regulator is bad. New regulator by the way.
 
Barry, I mis-spoke earlier. What I ~meant~ to say is Bugeyes don't use a voltage STABILIZER, IIRC. A device fitted to later (Mk-III and up, i think) cars to keep instrument supply voltage around 10V. Since that gauge is the right one, my question is answered. Sorry for any confusion.
 
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