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Problem After Hooking Up Battery Terminal Wrong

It was my own fault, and I should have taken the time to find a light to illuminate the dark garage where I had my 1979 MGB in storage.

What happend was for a minute, I hooked up the battery to the terminals the opposite way (positive on negative, negative on positive. I discovered my error and installed them correctly, and never attempted a start with the terminals hooked up the wrong way.

Right now, the MGB runs just fine, except that my ignition light is always on when the battery as soon as the battery is hooked up. As soon as the engine starts, the ignition light goes out.

In hooking up the battery wrong, did I fry out some relays in the alternator, and will a new one correct this problem?

Any advice is appreciated. Thanks in advance!

Bob Krzewinski Ypsilanti, Michigan

Reply to
Wolverbob
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You will have fried the regulator as well. Possibly also the zenner diode. Unless you know what you are doing with alternator electrics, get a new or exchange one. The alternator is not charging now so don't go any further than the battery will last. If you are not bothered about originality, now would be a good time to upgrade the alternator to a later model or one with higher output.

John

Reply to
John Manders

I'd expect parts of the alternator and the tachometer to be fried as these are the only electronic bits...

In message , Wolverbob writes

Reply to
Martin Akehurst

More than likely just a diode or two blown in the alternator, but they are probably in a pack and will need replacing as a pack. Take the alternator to an auto-electrician for a check.

That's what's supposed to happen, and indicates that the alternator is charging the battery.

No big deal, I wouldn't have thought.

Peter C.

Reply to
cornelp

The problem is that the ignition light is on as soon as the battery is connected. I assume that's before the ignition is on. On the ACR range fitted to the later MGB's, there are 2 permanent live feeds to the alternator. One is for voltage sensing and the other is the main alternator output. There is a feed to the warning light. This is unlikely to be from the ignition switch. The most likely scenario is that the voltage regulator has failed short circuit between the sense and warning light connections allowing a back feed. This is trying to supply the cars ignition load through the warning light and it lights up. The 9 alternator diodes are all on a common heat sink and cannot be changed independently. To buy a new diode pack, a regulator, a set of brushes (and new bearings while you're at it) is quite a cost and work. The job isn't too easy if you're not good with a soldering iron and electrics either. Sounds like a new alternator.

John

Reply to
John Manders

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