MG B electrics
Discussion
Getting fed up trying to decipher wiring diagrams in the Haynes manual, so thought I'd ask here:
Had some routine bad electrical faults over the years - left indicator freezing on, both indicators failing to work when the headlights were on sort of thing, then the front headlights working but not the rear. I decided to have a proper look at things last week, which led to me replacing the fuse box holder (4 fuse one) as it's a 78 B. This sorted the rear light problem, but not the rest. I therefore decided to replace a couple of the old female connectors that fit onto the spade connector ends that looked pretty corroded. I've now got working indicators and headlights, but an erratic brakelight, erratic fuel and temp gauge and erratic wipers and wiper. They sometimes all work properly, they often fail to work together, especially when there's bumps or hard cornering involved. This suggests another bad connection somewhere...
Long and short of the query is, does anyone know if these defective connections are likely to go through the fuse box or are they part of a relay somewhere that I can't figure out from the wiring diagram?
Had some routine bad electrical faults over the years - left indicator freezing on, both indicators failing to work when the headlights were on sort of thing, then the front headlights working but not the rear. I decided to have a proper look at things last week, which led to me replacing the fuse box holder (4 fuse one) as it's a 78 B. This sorted the rear light problem, but not the rest. I therefore decided to replace a couple of the old female connectors that fit onto the spade connector ends that looked pretty corroded. I've now got working indicators and headlights, but an erratic brakelight, erratic fuel and temp gauge and erratic wipers and wiper. They sometimes all work properly, they often fail to work together, especially when there's bumps or hard cornering involved. This suggests another bad connection somewhere...
Long and short of the query is, does anyone know if these defective connections are likely to go through the fuse box or are they part of a relay somewhere that I can't figure out from the wiring diagram?
The Advance autowire coloured diagrams are pretty good and easier to read than the Haynes.
The later car diagram is most of the way this PDF link (bottom right of each pic shows what year/model)
http://www.advanceautowire.com/mgb.pdf
Plenty on the web about earthing points as well to check and clean.
The later car diagram is most of the way this PDF link (bottom right of each pic shows what year/model)
http://www.advanceautowire.com/mgb.pdf
Plenty on the web about earthing points as well to check and clean.
I got plagued with electrical though.ts on various 'B's that SWMBO has had over the years.
I found the best way ( or start point) was to change all fuse holders and switches and clean all grounding points and major connectors. Takes a little time and a few quid but makes for a far more reliable car!
I found the best way ( or start point) was to change all fuse holders and switches and clean all grounding points and major connectors. Takes a little time and a few quid but makes for a far more reliable car!
In addition to the above, buy this book, follow the the detailed wiring diags and especially the lighting cct upgrade to stop current seep https://www.amazon.co.uk/MGB-Electrical-Systems-Up...
If you are keeping the car long term then might be worth thinking about a complete wiring loom replacement. They only last so long - if you try to replace a connector and find the wiring attached to it is tarnished and hard then it's probably end of life.
It takes time, and you have to remove and replace trim and dashboard but it's not hard providing you attack it systematically.
It takes time, and you have to remove and replace trim and dashboard but it's not hard providing you attack it systematically.
awooga said:
erratic brakelight, erratic fuel and temp gauge and erratic wipers and wiper. They sometimes all work properly, they often fail to work together, especially when there's bumps or hard cornering involved. This suggests another bad connection somewhere..
All typical symptoms of an intermittent in the white wire ignition circuit, a very common problem area.Well finally sorted it - looks like a bad connection and faulty earth on one of the black wires coming up from the ignition side. Cost me a fair few headaches, but only about 60p for the connector! Cheers for all the advice. Next stage is replacing the rad and having the manifold skimmed.
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