MGB & GT Forum

Hi All
I have finally finished the restoration of my B, but now have a weird electrical problem.
I know, a weird problem on a B? Wipers, fan blower and fuel gauge not working. Third fuse
blows about half the time. All exterior lights work. All connections seem to be ok.
Any suggestions will be much appreciated.
Thanks
Nick

All 3 on the same circuit. I would remove one at a time (disconnect) from power to find the culprit.
However, fuel gauge may not be working because float (sender) is not floating. Connect wire at sender to ground and see if gauge works with ignition on.

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"It is a mistake to try to look too far ahead. The chain of destiny can only be grasped one link at a time."
Sir Winston Churchill
---------------------------------------------------------------
"It all starts in your mind's eye, then it goes to your heart
and finally to your very soul."
G.S.George PHD

Thanks Robert. Sounds like the plan. I'll do that first
thing in the morning.

There are a few different wiring diagrams for the 76 - you are in green circuit from hell and you could have multiple problems.

If the temp guage is working then fuel gauge is probably a stand alone issue and maybe failed sender - temp and fuel are supplied by same votage stabilizer circuit.

All green circuits share the same fuse - any one item could be the issue. You have a "high resistance" circuit or you have a shart or an intermittent short.

How many green wires come off the fuse block? If two you are likely on diagram page 22 if three you could be on diagram 18.

The first step is to repeat teh fault - That is make the fuse blow by an action of yours. This would be operate each green circuit device one at a time and see if you can make the fuse blow.

If it doesnt I would leave something running (hazards for example) and then shake the wire looms to see if I could isolate an intermittmetnt short as noted by fuse blowing.

If all that failed you basically have a tough job ahead isolating each circuit.


I am hoping you say that it blows the fuse when you turn on the wipers or something. That would indicate high resistance in the wiper circuit.

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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

Thanks for the info Dan. I have 2 green wires from the 3rd fuse. Sometimes
the fuse blows immediately when the ignition is turned on. When it does not blow
the wipers and fan still do not work. The ignition switch is new. Could it possible be
the ignition relay? Looking at the diagram now.

I would unplug as many green circuits as possible - wiper washer, heater blower, induction heater, hazards - look at the diagram and figure out what you can access.

Then run it with those circuits disabled. If the fuse blows it's still one of the connected or (dreads) it's a wire short - very hard to find but a physical inspection may turn it up.

If the fuse doesn't blow you have a list of suspects and you can plug them in one at a time...

Oh - If I was a betting man I would bet on fan switch being bad. I replaced both hazard and fan switch on mine - hazards didn't work and fan didn't work - both cured with new switches. Do the hazards and turns work?

The second most likely culprint is the wiper motor. A failed motor will fail fuses but it would do it when you tried the wipers, not randomly as you say.

---

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 2015-07-29 06:49 PM by Ex-Calif.

Thanks Dan. I will try to do this tomorrow and post the results. I hope.
Green circuit from hell is correct.
Keeping my fingers crossed.
thanks again

Thanks for all the help everyone. I located the problem as instructed. It was a frayed wire
in the wiper circuit. Information was very helpful....thanks again Dan and Robert.
It works now

---

"It is a mistake to try to look too far ahead. The chain of destiny can only be grasped one link at a time."
Sir Winston Churchill
---------------------------------------------------------------
"It all starts in your mind's eye, then it goes to your heart
and finally to your very soul."
G.S.George PHD

Yay! Virtual confetti and balloons!

Glad it was an easy find!

---

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