Gas Guage Not Working--Voltage Stabilizer?

[BASS]

My gas guage suddenly stopped working (needle all the way to the E position)..I checked the voltage stabilizer (and the three wires that connect to it) that is mounted on the dash behind the glovebox, and it all seems ok (not corroded, and tight connections)..Can it be that this thing can still be bad internally??


Also, what is that blue thing thats mounted above the stabilizer in which a wire comes out of this blue thing and connects to the stabilizer?

 

[mightymidget]

I have just gone through this and have not completed the repair. If anyone feels I am giving wrong advice please straighten us out

1. To check the fuel gauge: Remove gauge the from dash and make sure housing is grounded

2. You have two wires going to gauge. a green wire that is striped and probably a black wire. (I am not sure about colors since I rewired my dash using my own colors)

3. Check the green wire on the back of gas gauge with a test light. The ignition switch should be on. Your test light should light up. do not remove this wire. if you have no power here go back to Voltage stab.

4. Make up a 24" jumper wire with a female wire fitting on one end and a alligator clip on the other. Test and find a good ground near the dash

5. With the power to the gas gauge (verified by test light earlier)Remove the other wire--probably black, then attach the jumper/test wire where that wire was hooked to back of gas gauge (opposite from power) and then clip the alligator clip to windsheild strut. or to the good ground you found earlier.

6. If gauge is in working condition the needle will slowly move from E to F as you ground the jumper wire from the back of the gauge

Ok if this works then move to the gas tank. You have a bad ground at tank /sending unit, or sending unit is not working.

 

[mightymidget]

In regards to your VS (voltage Stabilizer) I did a little trouble shooting with it also

At first I was getting the same voltage reading going in and out of the VS, seems you have three wires, mine were two green stripped wires, with different color stripes, your third wire probably goes to another instrument.

I knew that was wrong. the VS should have battery voltage going in and alternating voltage coming out. So I gently took the VS apart and cleaned the VS points and made sure the internal VS ground was clean and attached.

Then I cleanned off the mounting ear. I bench tested it and it did fine. so I reinstalled it. The VS MUST be grounded to body of car by the mounting ear and attaching screw.

The VS is very simply made but very fragil, so be careful taking it apart

 

[dklawson]

All that I can add to the information above is that if you determine the problem is the voltage stabilizer, Moss now sells solid-state replacements for a very reasonable price. Consider it if you need to replace the stabilizer.

If you are more adventurous, I have a PDF on troubleshooting the gauges, repairing the Smiths stabilizer, and making your own voltage stabilizer. You can see the document using the link below.
https://home.mindspring.com/~purlawson/files/SmithsVoltageStabilizer.pdf

 

[BASS]

Ok, the VS can actually swivel around, so it looks like there may possibly be a missing (bottom) mounting tab thats supposed to go into the sheetmetal? Im going to remove it later on today and inspect this more....

 

[dklawson]

The stabilizer needs a good clean mounting surface as the metal can is the earth connection. If the stabilizer and mounting area are rusty, that can be one problem. There is also an earth wire pinched between the stabilizer's metal can and the its circuit board. If that area is rusty, the stabilizer will need additional help to restore that connection.

If the points inside the stabilizer are oxidized and/or burnt, the circuit will appear "open" with no output voltage on the stabilizer's "I" terminal. If the points are OK and the stabilizer has lost its ground, it will pass full system voltage and the gauges will work but read too high.

 

[BASS]

Ok, I removed the VS and it appears ok, but I didnt open it..I think I will just buy a new one ($17) from MOSS..

Also, what is that blue circular thing (which has its own mounting tab) that attaches to the VS? Does the new VS come with that blue thing?

 

[dklawson]

I am not familiar with a blue circular part mounted near the stabilizer. Perhaps it is a capacitor used as a noise suppressor. How is it attached to the voltage stabilizer?

 

[BASS]

Ok, its a blue circular thing that is attached to a tab that mounts to the same mounting tab as the VS. It has a black wire coming out of it, and the other end goes to one of the B terminals on the VS itself..

It says "Dubilier" on it, along with "British Patents". Its also marked type SV, in addition to 150 V.DC.WKG.

 

[Darwin]

It is indeed a capacitor made by Dubilier. What it is doing there is anybody's guess. Probably used tosmoothe the on/off action of the stabilizer, but I would think that would negate the VS's fuction.
Wait a minute... I see that it is attached to the B post. That would help stabilize the input voltage from the battery and overcome spikes as the alternator/generator engages and disengages.

 

[dklawson]

That sounds right to me. I've never seen one installed on the stabilizer before. Perhaps a previous owner was trying to filter every electrical device on your car to improve how its radio sounded.

 

[BASS]

Ok guys, after 6 months of hibernation, I got around to installing a new voltage stabilizer, and the gas gauge now works!! In addition, my temp gauge now works also (I was about to install a new temp sender sensor thinking that was the problem...)..

Now for my next project, installing a new cd radio..

 

[dklawson]

I have radios in my British cars. They are great at stoplights, useless at all other times.

I'm glad you got the gauges working again.

 

[bugedd]

Can someone tell me where the voltage stabilizer is? My fuel gauge has been acting crazy, maybe that is the issue.

 

[BASS]

Not sure about other cars, but for my 79 its in the glovebox compartment (open the door, and its mounted on the top near the latch)..You need a stubby screwdriver to remove it (one screw)..

 

[dklawson]

Bugedd, if the fuel gauge you are asking about is in the '60 Bugeye, you won't have the voltage stabilizer.

The early gauge systems on BMC cars (before the mid-1960s) did not have them. That gauge system is very different. If the gauge is working at all, start by investigating ALL the ground connections. That includes the gauge case itself. It is not necessary to ground the late style gauges... except for illumination. It IS necessary for the early gauges to have a good case ground connection.

You will find almost all you need to know about the early gauge system on Barney Gaylord's MGA Guru web site. See the link below.

https://mgaguru.com/mgtech/electric/fg_01.htm

 

[Sarastro]

Yeah, the Bugeye uses a digital fuel gauge--it's either full or empty; no in-between.

Sorry.

Seriously, if you want to make the solid-state regulator in the document Doug has written, you can get an LM317T from Electronix Express for 35 cents (https://www.elexp.com/ics_309k.htm; second item in the list). Probably a bit less than Moss charges for the same thing.

EE also has the LM337T for positive ground, but it's much more expensive (75 cents).

 

[dklawson]

Thanks Steve. However, I think Moss has done a very good job of reducing the cost of their solid-state voltage stabilizer. It is MUCH less expensive than a NOS Smiths part and I'm sure it will be more stable and reliable.

For the last two negative ground applications I worked on, I used a high-current version of the 7810 chip with nothing more than wires (and heat shrink) attached to the chip leads. That's very inexpensive and quick.

The voltage stabilizer picture in the link below is from my friend Wes. A DIY voltage stabilizer doesn't get much simpler than that.
https://www.adocars.com/elf-ado/elf/elfimages/v-reg.jpg