My passengers

[Kim de B]

Went to an MG club picnic last night, about 40 minutes south of home. On the way down, in a hard rain, noticed the generator light in my 66B glowing just barely and wipers and turn signals slow.

Uh oh.

When we got there, I asked some of the guys to help me check it out. Tried to start the car, but it wouldn't. Went to check the battery connections, and here's what I found:

Hitch hiker photos

This wasn't what was wrong with the car, but it sure was amusing... (This is my Ofoto site. Sorry, but you'll have to sign on to see the pictures. It's free, but annoying. Someday I'll get my own site, so I can post photos here that show up...)

Anyway, after I took care of this problem, one of my friends gave me a fresh battery, and we left before we needed headlights to get home.

With the new battery in, it started right up, but apparently was not getting a charge from the generator. (This is a 66B, positive ground.) We checked it with a voltmeter. Read 12v off fresh battery, but voltage dropped sharply when I switched the lights on, and didn't go up from 12v at all when revved.

Generator light started glowing softly again after about 10 minutes on the road, but we made it home OK at dusk with no lights.

I'm suspecting the voltage regulator. Connections all seem to be good, and I know the brushes in the generator are OK.

 

[JordanB]

Please excuse my naiveness on the positive ground subject,

but. I had this exact problem on an old chevy pick-up I had (excluding the mice). Turned out that I needed a new alternator. Ran great, and powered everything after the new install.

 

[Lurker]

I have no background at all with positive grounds, but that won't stop me from replying to your post.
If you put you volt meter across the battery, it should read something like 12 to 14 volts. Start the car and the volt meter should increase to something like 14.3 volts. Rev the engine and it should hold steady at 14.3.
If you don't get 14 volts with the engine running the problem is the alternator (generator). Before you change that out, check for a loose belt or bad, dirty electrical connections. Also make sure you have a good connection for the battery ground to the chassis.
If the voltage doesn't hold steady when you rev the engine, especially if the voltage climbs way above 14.3 volts, then you have a regulator problem.
Good luck, and have fun.

 

[aerog]

Lurker: Quite a few modern alternators have built-in regulators so the whole unit is sent off for repair (or replaced). Checking the voltage at the battery (essentially checking the output of the voltage regulator in other words) only narrows it down to either the generator or regulator. If you check the voltage at the input-posts on the regulator you'll be better able to determine whether the regulator or generator is at fault.

I suspect you're right Kim - it could well be (most likely is) the regulator and not the generator. I had a similar problem happen on my MGTD replica with the original 1969/70 Bosch Generator. I replaced the regulator with an "authentic" one that was a couple of diodes and a relay. After experiencing a toasted regulator (that was fun - flash - fire - flash - poof) I put a solid state one in, lasted for months... then during a parade it quit on me.

My new 50amp Bosch alternator with built-in regulator works a whole lot better now

 

[aeronca65t]

Most of these pos ground Brit cars have a voltage regulator that has a removable cover. The voltage regulator has "points" under the cover (several sets.....they look like distributor points) that can get burned with time.....you can try filing them down a bit but it's probably time to get a new regulator if they're that burned. If you can hold one of the point sets closed temporarily using a wooden dowel or similar(I forget which point set......I think this is called "full fielding", so it's probably the field points) and the car starts charging, this usually means the regulator needs replacing. The points shouldn't be held closed more than about 10-15 seconds.

[ 06-20-2002: Message edited by: aeronca65t ]</p>

 

[Kim de B]

Thanks, guys. Yep, I have a separate regulator. Haven't had a chance to check it out yet, but thanks for the suggestions. I'm going to have to take it in to my MG mechanic this weekend, because I just don't have time to figure it out myself.

Next Saturday morning, bright and early, we're driving it to Texas for the big NAMGBR show. Yee-haw! We're caravaning with a group from Long Island to meet up with another group in Indiana. Fourteen MGs in all making trip down to Dallas.

Hope we make it!