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MG MGB Technical - No electrics

My 1965 MGB has been checked over the winter period but at last check no turnover. I put the batteries on charge but now have no power output at all.

Checked fuses etc but seem ok. Tried top jump start but absolutely nothing - no ignition light etc

Can anyone advise please
Trevor Pearce

Trevor. No electrics at all indicate that either both batteries are dead, that there is no connection between the two batteries, or that there is a bad connection at the earth and/or the line going to the starter solenoid.

Use a test light and test the various connections to see where the bad one(s) is/are. If you can find a bad connection, clean and tighten the connection, then keep going forwards until you have both a good ground, at the battery, and good power at the starter solenoid (check it under load, using a volt meter, if you can recruit an assistant, or make up a jumper lead that will allow you to take a voltage reading while trying to start the engine).

Let us know what you have checked out and what your finding are. Sounds like some corroded connections have developed over the winter and are the root cause of your problem.

Les
Les Bengtson

This happened to mine, while undergoing an MOT at Halfords and had the mechanics there completely stumped!

In my case it was a bad connection at the solenoid, I removed the battery cable and browns from the solenoid stud, cleaned them up, reassembled with copper grease and it has been fine since.

Yours should be easer to diagnose with the solenoid on the inner wing (I presume). Turn the headlight switch on, and if they come on the batteries and their conenctions are OK, so jump straight to 4. below

1. If not check for 12v between a good earthing point on the body and the edge of the battery cable lug. If you see 12v the battery and its connections are OK, if not then with the headlight switch on you need to go back to the batteries and test across both, then each to work out which one of the connections is bad. Also measure direct on the posts of each battery to make sure that each is showing 6v.

2. If you have 12v on the battery cable lug at the solenoid and the body in the first test check the stud the battery cable is bolted to, and then the conenctor on the brown wire at the solenoid. You should have 12v on both, if not on the first remove the battery cable and clean it, if not the second remove the brown wire and clean or replace the spade or connector.

3. If you have 12v on all those points on the solenoid check the linked 'B' spades on the control box and the connectors on the three browns that should be there. At this point the brown splits off one way to the fusebox to power the horns and lights, and the other way to the ignition switch. If you have no lights or ignition, you have at least two problems.

4. If you have lights but no ignition just check for 12v on the brown at the ignition switch while you turn the switch first to the ignition position and then to the start. If you lose 12v at any point there is a bad connection or broken wire leading back to the control box. If 12v doesn't appear on the white (ignition) or white/red (start) when the key is turned then the switch is faulty.
Paul Hunt

Check the connections on the battery posts are tight even if they look ok.
Richard Atkinson

Better yet, take the connections off the battery posts and clean the corrosion out of them.
Matt Kulka

Apologies, I forgot you mentioned a jump start did nothing to help. Corrosion on the battery clamps wouldn't keep a jumpstart from helping.
Matt Kulka

If you happen to have battery cables where the battery connector is molded over the cable give each cable a good pull. I have seen the wire corrode inside the terminal and it is invisable from the outside.
John H

This thread was discussed between 09/04/2009 and 14/04/2009

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