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tach and fuel gauge problems

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Sinker Avatar
Sinker Jerry Lane
Milton, FL, USA   USA
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1967 MG MGB GT Special "Betty White"
I hope someone has had this problem and can help me sort it out.
We were on our way to show in Betty a couple of weeks ago and lost the fuel gauge and tach when we turned on the turn signal. I got them working again to day by jiggling some wires and replacing a connector. Everything was fine until i turned on the interior fan, same problem but this time no brake lights. We are off to another show Saturday and i would like to get this fixed before then.
Anyone have any ideas?

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lewisrn Avatar
lewisrn Gold Member Bob L
Danville, IN, USA   USA
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1980 MG MGB "The "B"
Hi Jerry. Obviously you have wiring/ground issues. Find the appropriate easy to read, color coded wiring diagram at the following link and use it to track down your problem:

http://www.advanceautowire.com/mgb.pdf

There are always people here to answer questions while you are troubleshooting.



“Ideological certainty easily degenerates into an insistence upon ignorance". Daniel Patrick Moynihan

In any debate, the side which strays from civil discussion is usually the side that lacks confidence in its debate position or in the merit of their arguments. Making personal attacks on the opponents instead of staying on the subject is also a sign of weakness.

Anyone who feels compelled to respond in kind to any perceived slight is often suffering from narcissism.

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rntanner Roger N. Tanner (Disabled)
Oxnard, CA, USA   USA
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1970 MG MGB
1977 MG MGB
Bring up this webpage:

http://www.advanceautowire.com/mgb.pdf

Sheets 2 and 3 cover your year model.

The tachometer works off of pulses on the Ignition Coil. Top-Center of both sheets.

The "GAUGE VOLTAGE STABILIZER" is the mostly likely "bad component."

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=123897

. . . and modern "solid-state" versions are available:

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=for+sale+MGB+gauge+voltage+stabilizer+for+1967&tbm=shop

$15.11 US dollars.



Roger N. Tanner
Professional Engineer, Retired

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Sinker Avatar
Sinker Jerry Lane
Milton, FL, USA   USA
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1967 MG MGB GT Special "Betty White"
Any idea where the stabilizer is located?

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Sinker Jerry Lane
Milton, FL, USA   USA
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1967 MG MGB GT Special "Betty White"
IMG_1954.JPG (487KB)
i found this under the dash.

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kuz1 Avatar
kuz1 Keith Kuzma
Prattville, AL, USA   USA
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the voltage stabilizer has nothing to do with the tach , so no it isnt the "most likely" culprit

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Ex-Calif Gold Member Dan D
Dayton, OH, USA   USA
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1968 MG MGB GT "Bart - Yellow And Naughty"
1977 MG MGB "Red Betty"
2006 Suzuki Grand Vitara "Suzi Q"
2012 Jeep Liberty "Tommy The Tank"
On the '67 the tach and the fuel gauge are powered by Green circuits.

The tach supply tees off the spades at the voltage stabilizer on the "B" side of the VS. The VS is also (obviously) powered by the same green t joint here..

Depending on the nuance of your 67 there are either 3 green wires on the VS or 4 (67 with no hazard flashers).

FYI the other items powered off this tee joint are heater fan and turn signals (for 67 with no hazard flashers)

Most probably cause - especially if jiggling fixes it, is a loose/dirty spade at the VS "B" terminal.



The goal - Reliable summer driver interspersed with mechanical tinkering...
Motto - "Driving fifty in the twisties..."
On Mods - It's your damn car - Do what you want. Haters gonna hate...
On SUVs - Drive your B like a soccer mom is texting her friends about how she wants to kill you...
Red Betty - http://www.mgexp.com/registry/GHN5UH418165
Bart - http://www.mgexp.com/registry/GHD4U146898G

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Sinker Avatar
Sinker Jerry Lane
Milton, FL, USA   USA
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1967 MG MGB GT Special "Betty White"
That could be the problem Dan. When things do work and the turn signal is activated, fan switched on or brake applied the tach and fuel gauge goes down.
Now if I can only find vs.

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Ex-Calif Avatar
Ex-Calif Gold Member Dan D
Dayton, OH, USA   USA
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1968 MG MGB GT "Bart - Yellow And Naughty"
1977 MG MGB "Red Betty"
2006 Suzuki Grand Vitara "Suzi Q"
2012 Jeep Liberty "Tommy The Tank"
On the 68 the VS tucked tight against the back of the dash on the left side. Sort of inline with the fuel gauge & heater control

The brake being applied adds a new twist. I now presume you have no hazard flashers and you have the 2 fuse fuse box.

You will also need to check at the top fuse position (the greens) remove clean and tighten here.

If the reverse lights are squirelly as well the fuse box connection is becoming more likely.

Clean and tighten up both - you can tighten spade gently with a pair of pliers.

Here's a shot of my 68 when I was cleaning up 48 years of PO bodge jobs behind the console.

In reply to # 3383115 by Sinker That could be the problem Dan. When things do work and the turn signal is activated, fan switched on or brake applied the tach and fuel gauge goes down.
Now if I can only find vs.



The goal - Reliable summer driver interspersed with mechanical tinkering...
Motto - "Driving fifty in the twisties..."
On Mods - It's your damn car - Do what you want. Haters gonna hate...
On SUVs - Drive your B like a soccer mom is texting her friends about how she wants to kill you...
Red Betty - http://www.mgexp.com/registry/GHN5UH418165
Bart - http://www.mgexp.com/registry/GHD4U146898G



Edited 1 time(s). Last edit at 2016-10-28 11:06 AM by Ex-Calif.


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2015-11-02 20.20.41.jpg

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Simon Austin Avatar
Surrey, BC, Canada   CAN
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Jerry,

Have a look at the fuse on the white wire/green wire circuit. On your car, you only have two fuses so will be easy to find.

Even if the fuse looks good, swap it for another. If that doesn't fix your issue, the fuse box contacts might need a thorough inspection and cleaning.

I'll bet you'll find you've got issues with other components on the green wire circuit.

The VS is located under the dash above your left knee. There's a good photo somewhere on here showing its location. If I can't find it, I'll take one off my car.

If the supply to the VS is interrupted (as mentioned above), you'll experience the issues you describe.



"Speed costs........how fast you want to spend?"

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Sinker Avatar
Sinker Jerry Lane
Milton, FL, USA   USA
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1967 MG MGB GT Special "Betty White"
After all this trouble I found a loose spade connector on the fuse block. It would seem everything is back to normal.
Thank you everyone for the help and suggestions.

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Simon Austin Avatar
Surrey, BC, Canada   CAN
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Nice work, Jerry. thumbs up



"Speed costs........how fast you want to spend?"

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