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MG MGB Technical - Head lamp flicker

OK guys, i've search the archives for this but no help. I've noticed recently when i start my 73 at night and turn the headlights on they will flicker a couple of times when i rev the engine. Did this before and after alternator replacement. BTW the old alt.(6 months!) was a 43 amp Lucas that was only puttting out 20 amps. Did the Bosch conversion today, got a rebuilt Fiesta unit from Autozone, came with fan and pulley. Had to trim bracket for fan clearance and get 1" longer fan belt. Plugged right up and i love it so far. Also cleaned all my electrical connections a couple of weeks ago. Think i might have missed something? Also noticed fuel and temp gages sometimes stop then come back up. I think i need to clean the voltage stabiliser for those but am stumped by the headlight flicker. Just started doing it right before i cleaned everything. Have thought about replacing all the bullet connectors. Anyone know how many single and double ones i need to order? Or you gonna make me go out there and count them all? LOL. Thanks in advance.
James Skinner

It seems as though you've done everything I would've, myself.

Checked & cleaned all the connections at the fuse box ?

Have you checked & cleaned all the connections at the starter solenoid? The brown wire at the starter
solenoid uses a push-on spade connector and this often becomes dirty and coated with oil and
loosens it's grip and electrical integrity with age, heat, and engine shake.

Check all of the grounds (black)? Engine ground strap?

BTW - did you run a parallel wire from the Bosch alt to the starter solenoid? This isn't mandatory, and it
won't exactly solve your ongoing problems in and of itself - but running a #10 wire, in parallel with the
thick brown wire (that runs from the alt to the starter soleniod) helps alleviate any resistance (and heat
build-up in the original wire harness) that the extra amps might cause. There's an extra male spade
connector on the Bosch alt that makes this an easy task. You'll need another ring-tab connector at the
starter soleniod, though.
Daniel Wong

James,
When you wer cleaning connectios, did you include the engine to chassis ground strap (I believe it's on the transmission cross member on a '73) ??
Additionally, a marginal ground at either the battery or alternator will cause similar problems.

FWIW, Ed in 'ole Virginny
Ed Meadors III

Thanks guys. Yes i cleaned the fuse box and all the grounds, also wires at the starter. Guess i need to go over everything again. Maybe i left a wire loose somewhere? Will let you know if i find anything.
James Skinner

Are they flickering right off or just flickering between 12v (no charge) and 14v (charge)? Does the ignition warning light stay off (always assuming it works correctly)?
Paul Hunt

A buddy has a shirt that has a Lucas three position switch illustrated. The positions are "Off, Dim and Flicker".

Seriously, though, I had a similar problem with my B. My gearhead buddy and I both decided to add relays for the lights, and it seemed to solve the problem. The headlamps run full amperage through the switch, and that seemed to be the cause of the flickering. He's an electrical engineer, so it wasn't a complicated project for him.
Craig Cody

Oh...I almost forgot to mention this! There is a booklet called "Lucas Fault Diagnosis Manual". It is Moss part # 990-035, and sells for $6.75. Worth it's weight in gold for analyzing just about any problem you might have with the electrical system. It tells how to use a voltmeter for various tests to determine what your problem might be. It even includes the specs for aligning the headlamps, etc. Really a handy item.
Craig Cody

Think i've got it fixed. Retightened the new fan belt i put on yesterday and cleaned the voltage stabiliser too. The Bosch alt. is great so far. With lights, heater fan and wipers on it seems to handle the load with no problems. Ignition light goes out as soon as the car starts. I did notice my voltage stabiliser wasn't mounted very securely and is mounted on some factory tar like sealant. Scraped it away where it mounts and used a slightly larger screw to mount it. Think i'm going to add relays also just to be on the safe side. Really appreciate all the help guys.
James Skinner

This thread was discussed on 14/11/2001

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