MGB Register Forum

Hi,
I am a new member to the forum even though I have been a member of the MG Car Club for many years. I have a 1981 MGB roadster that I have had from new. Apart from doing the usual repairs and maintenance, it had a major mechanical overhaul in 2007. I have recently noticed a potential problem with the ignition light. The car starts as normal and the ignition warning light comes on brightly on starting as it should and then goes out - well, nearly goes out. When the engine is running I can see that the ignition light has a very faint glow. The alternator was replaced in 2007 (only some 1500 miles ago). What is the problem and what should I do about it? Any advice would be most welcome.
Allan Reynolds (Shropshire)

Hi Allan, most likely an alternator fault (of course) although car electrics are not my strongest point.

See this link to the US MG Experience website: http://www.mgexp.com/phorum/read.php?1, ... sg-3523793

Here is one quote from the thread referred to:

Your "ignition" lamp (which is really an alternator lamp) should be off when the key is off, on when the key is in the ignition position but the engine not running, go off when the engine is started and hits about 1100 or 1200 RPM and remain 100% completely off at all RPM above 800. If the lamp is on or even glowing dimly you have an alternator fault. The most likely cause is the rectifier pack in the alternator. First check the connector and connections to make certain that they are clean and not corroded.

Hope this helps

Ian F

Many thanks, Ian. I'll look into that.
Allan

Hi Allan,
good luck with it - alternators (in my opinion) are just about the most sensitive item on a vehicle - easily damaged by disconnected wiring, poor connections and any electrical welding (MIG etc). Also a little difficult to check for the average home mechanic. Good news is that MGB alternators are relatively inexpensive compared to anything for a modern car, so replacement might be the simplest answer for you after checking all the wiring?

Ian F

Hi Allan,
I would also check that you have good earth connections. Particularly the battery to the body and the earth from the body to the gearbox - which on a late car is at the back of the gearbox. I had a problem a few years ago with a poor earth on my 1979 GT ( for a different totally reason) and fixed an earth strap between the engine and body in similar position to the original design.

Geoff

Quite a lot has been written about problems revolving around the ignition light glowing here:
http://mgbforum.mgb-register.org/viewto ... ?f=4&t=385
You may find some useful info within this to help locate your problem.

I am also a new member to the forum and I wonder if a member has already seen the lens of the warning lamp of the ignition light becoming dark and no longer allowing the light of the bulb located behind the dial to be seen? I also test with a small flashlight and have the same problem.
Francois