MGB Electrical fault - Fuse blowing

[sugarflux]

Hi there
Anyone able to help please? I've recently acquired a 1978 MGB GT Coupe.

The rear-passenger-side light isn't working and i've tracked the problem down to a blown fuse. However, every time i replace the fuse it works for a few minutes and then blows again.

(Also the rear-passenger-side number-plate light won't work even with the fuse replaced so may need re-wiring. I don't know know if this could be related to the above?)

They are 35amp glass fuses. The fuse box fits four and the other three are all fine.

I'm a beginner to car repair and am using the opportunity to attempt to learn but i'm a little stumped!

Please help!
Thanks

 

[breezer]

as the fuse blows its fairly safe to say there is a problem.

The fact the fuse doesnt go imeadiatly suggests its not a dead short, so i would there for assume a chaffed wire, as for where that i cant tell you.

I could however suggest that if there has been any welding done on the bodywork/ chasis to look there first

 

[sugarflux]

Thanks breezer

I'll take a look and see if i can find anything like this

 

[breezer]

sorry, i forgot to mention, it may also be wear and tear, more tear than ware.

It may be a gromet (no wallice) has worn out / fallen down and the cable is free to rub and tear

 

[empip]

You need a manual .. with wiring diagram etc.
Check under carpets etc... maybe behind headlining .. try tracing wiring back from the light unit ...

I have:
'76 MGB GT, ~30mpg
'80 Mini 850cc, consistantly 40mpg
'87 Opel Manta (slightly modified, ok a fair bit) consistently 32mpg
'98 Escort (her car) average 35mpg

Here ..
//www.diynot.com/forums/viewtopic.php?t=34979&postdays=0&postorder=asc&highlight=mgb&start=15

There must be a 'Bee' owners club on line similar to 'Masam' (Midget and sprite club)? If so try them they'll know all there is to know, no doubt.
Be lucky.. You may need to bee in a Leylandi machine.. ''''''''

 

[keyplayer]

Change the number plate bulb first of all - there is a good chance that it has blown but a bit of the filament has shorted within the bulb. Not uncommon.