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fuse problem

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M

MGB_80

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well the MG keeps blown fuses...the one that keeps blown is the fuse for the brake lights, coolant temp, and fuel gauge...check for shorts in the wires but haven't found anything...can take the car out for around 30 mins before the fuse blows any ideas on how to fix it
 
Unplug all the green wires going to the fuse box.
Plug the wire for the brake lights to the fuse box and go for a drive and see if the fuse blows. If yes, you have isolated the part of the circuit that is causing the problem. If not, plug in another green wire and see if it causes the fuse to blow.
Once you have isolated the branch of the circuit, unplug parts of it to isolate the problem.
 
Hello MGB80,

it is likely to be a chafed wire where it passes through the body somewhere. If those are the only components on the fuse, a short in the temperature or fuel gauge sensor wires would not blow the fuse, just make the instrument read high.
So it is either the brake lights circuit (most likely) or the feed from the fuse to the instruments (via the voltage regulator)
Once you have isolated which circuit is the cause, as Kimberly suggests, then look for likely spots where the cable may be damaged or trapped.

Alec
 
MG80 - Following Kimberly's troubleshooting suggestion, if the fuse blows when applying the brakes, look at the wires going into the lamp socket of the brake light on each side of the car. I had a similiar experience in our MGB while on a trip and finally traced it to the wire going into the socket for the right brake light. It seems that the perfect place to stash my camera case in a very full trunk was the right hand fender well, just ahead of the tail light/brake light asembly and the camera case was bending the wire for the brake light hard against the edge of the socket - sufficiently hard to cut through the insulation and cause a short.

If you find that this is the problem, contact me, because when we got home, I proceded to make up protective covers to go over the light sockets to prevent the problem. I have pictures of my covers and information on making them out of PVC pipe.
Cheers,
 
David_DuBois said:
MG80 - Following Kimberly's troubleshooting suggestion, if the fuse blows when applying the brakes, look at the wires going into the lamp socket of the brake light on each side of the car. I had a similiar experience in our MGB while on a trip and finally traced it to the wire going into the socket for the right brake light. It seems that the perfect place to stash my camera case in a very full trunk was the right hand fender well, just ahead of the tail light/brake light asembly and the camera case was bending the wire for the brake light hard against the edge of the socket - sufficiently hard to cut through the insulation and cause a short.

If you find that this is the problem, contact me, because when we got home, I proceded to make up protective covers to go over the light sockets to prevent the problem. I have pictures of my covers and information on making them out of PVC pipe.
Cheers,
Click to expand...

My problem was a wire pinched in the top for the pedal box. Being methodical, it took me less than an hour to locate and fix.
 
ok turns out it is not a green wire...pulled the wires that run to the fuse unit relay (relay near front of car to right of fuse box) first was a brown/white wire then narrowed it down to a brown wire that runs to the starter solenoid...IIRC the wire runs from the solenoid to the relay to the fuse box...when i plug this wire into the fuse box it blows...looked at the starter and adjusted the wires incase they were grounding out...fuse still blows...could i have narrowed it down to the relay?
 
The relay and the white/brown wire is not fused and therefore cannot cause the fuse to blow. Unplug all the green wires to the fuse box and see if the fuse still blows. Plug one green wire into the fuse box and try all the lights and accessories and see if the fuse blows. Repeat with the rest of the green wires.
When I had the short in my car, the fuse would not blow until I closed the brake light switch.
 
Yes, for testing purposes the car has to be on to energize the white/brown wire. Unplug all the green wires before turning the car on.
 
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