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MG TD TF 1500 - Generator/Regulator/Cut-Out Issue

Gentlemen -
I am chasing down a problem and am in need of the collective wisdom of the group. I am attempting to resolve a charging issue on a TD and I am baffled by the behavior that I am seeing in the charging circuit.

After polorizing the generator, I crank the TD and see that the ignition warning light will go completely out after reving the engine slightly - the Ammeter will show a charge. The needle (which seems very sensitive and flicks quite noticeably with every fuel pump click) will show a charge of about 13-15 amps at low to normal speeds. Note that I have charged the battery before running the car. The segmented belt is tight enough to do the job - but not too tight.

On test drives, the ignition light will remain out until I slow down to an idle speed at a stop sign or traffic light. Then, the light will slowly come back on - in a dim state. If the engine is allowed to remain at low idle, the light will then come on full, bright red and will remain on bright red - regardless of engine speed. No charging will take place following what I am thinking is a collapse of the charging field.

If I return home and reflash (repolorize) the generator, the light will once again behave as above - indicating charging initially and then not charging at the low idle speed - followed by the full red glow of the warning lamp.

Is this a generator problem (had it checked and was told all was OK - putting out over 17 amps)? Or is this a control box problem on the cut-out side? Or is the problem in the actual regulator side of the control box?

I have several control boxes and one has been modified by Mr. Jeffers - all display the same symptom - which makes me think I have a problem in the field coils of the generator - or with the armature - problems which show up after a 20 minute service in charging. PLease note that the dim operation of the warning light will also take place following initial start up - if the engine is not kept at a speed slightly above idle.

I am totally baffled and am hoping you all might have some good advice - I will admit to being at a loss - I am only able to work on this car in short 2 hour sessions and I imagine my approach has been somewhat erratic and I admit that I have not moved through options in a methodical manner.

Any thoughts would be appreciated - thanks in advance.

Jeff Delk
Jeff Delk

The generator cannot put out decent voltage at idle, so the battery is able to light the warning light indicating a state of discharge. That's normal no matter if at startup or full warmed up.
"the light will then come on full, bright red and will remain on bright red - regardless of engine speed" is troubling. "I have several control boxes and one has been modified by Mr. Jeffers - all display the same symptom" would suggest it isn't a regulator problem.
I'd recommend tapping a voltmeter in and watching the real behavior to verify your warning light is telling you the truth at all times. I installed one in the instrument cluster and it is rather interesting to observe, especially with headlights on trapped in stop and go traffic! It would be the first time the warning circuit was compromised, by an intermittent short, but that isn't a common scenario.
What you describe could be brushes worn down to zilch. The field coils and armature would completely fail, and not display the intermittent behavior.
JIM NORTHRUP SR

Put the voltmeter on the large bolt terminal of the generator. Compare the readings on first start-up and at the stop lights. I think you will find that something about the generator is not giving the output it should at the stoplight and after.

Note Mr. Jeffers was my father.
Cheers,
Bob
Bob Jeffers

Thanks for the quick replies. And Bob, I will address you properly as "Bob" moving forward! The generator brushes seem fine to me - plenty of material. What strikes me as odd is the seemingly proper function of the generator - and the dramatic cut on of the light - which can then be made to go out by simple polarization.

Jeff Delk

Jeff

Here is a link to a doco regarding everything Lucas

http://www.atcc.org.nz/tcc/LucasFault.pdf

You may find it useful to fault find your problem.


Graeme
G Evans

Hi Jeff,
also try
www.healey6.com/bulletin
Ray TF 2884
Ray Lee

This thread was discussed between 07/04/2013 and 08/04/2013

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