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MG TD TF 1500 - Generator Battery Relationship

I've just suffered the second generator failure in four years and am a bit perplexed. The car (TF) had been laid up for about 9 months, battery disconnected, while we house renovated and had no spare time at all. About 6 weeks ago after a brief charge of about an hour, the engine fired up pretty quickly although it ran a bit unevenly due mainly to the fuel deterioration over time. A refuel and new plugs fixed that. I did a few short runs of about 25km and occasionally the generator light would be illuminated until revs got to about 2500-3000. Then, this symptom disappeared and all seemed well. Last weekend we went on a fairly long run of about 170km and again, judging from the ammeter, all looked good until about 20 mins from home the generator light came on, and stayed on.

Checking when at home the voltage on the battery was about 12.4 and specific gravity only fair, but the engine cranked very freely on the starter. I did a complete charge including what the charger calls a 'recondition' phase. After a pause at the end the voltage was 12.65 and specific gravity was improved but still in the borderline 'fair' to 'good' range. One cell previously had got a bit short of fluid and the top of the plates were exposed (a bit)but its SG was not greatly different from the others.
On starting after recharge(a very easy start) there was no change to the behaviour of the gen light - it was permanently on. I tried an old voltage regulator (coil type)with no change to the result. I then checked the field coil resistance and it came to 3ohm - so it seems I have a short there.

The generator is about 4 years old as is the battery, and I was hoping it would be the last generator I'd have to worry about, but one things springs to mind - can a slightly decrepit battery (which I will certainly replace)lead to internal generator problems or is it just happenstance that the generator died when the battery had the flu?

Also any ideas on where I go from here would be great, as I don't want to have sell any more of my wife's jewellery to fund yet another expensive generator replacement. I can only just read a multimeter, so any complicated engineering is beyond me but I'm willing to give anything a try. I just don't want to have this experience again (she said).
John Hoey

John,
IMHO, it sounds like the generator needs to be replaced,,, but just saying that it is 4 years old doesn't relly say anything about its condition,, If it has a lot of miles on it, replace it,,, If it only has a fwe thousand miles on it, it might be that the belt was too tight, OR way too loose.. remove the belt and spin the genny,, see it if makes and rubbing or grinding noise,,
take it to an auto electric place anfd they can check it out,,

SPW
STEVE WINCZE

I used this Lucas "Generator and Control Box Tests" publication to track down the problem with the generator in my TF. The generator tests only require a simple volt meter. The four simple generator tests pointed me toward a problem with the armature. Yep - one of the "fingers" of the commutator was broken. The regulator tests in the Lucas publication require an analog volt meter.
http://mgaguru.com/mgtech/books/pdf/Lucas_Generator_and_Control_Box_Tests.pdf

In addition to the WSM, here are two Lucas Overseas Technical Correspondence Course publications that may also help diagnose and fix the problem.
>> Section 4 - Generators
http://www.fromtheframeup.com/uploads/Lucas04_Generators.pdf
>> Section 5 - Generator Output Control
http://www.fromtheframeup.com/uploads/Lucas05_Generator_Output_Control.pdf

Yes, the voltage regulator must be adjusted to match the generator.

The regulator on my '54 Chevy truck caused the generator to over charge and melted the solder in the armature. Here is a photo of the trail of solder that was slung off onto the inside of the Chevrolet generator case.

Lonnie
TF7211


LM Cook

Lonnie: Great research, info and materials.
Chris Couper

I've replaced both the ginny (aftermarket look-aloke from LBC that is performing well into its second year) and the control box from M. A cheap Auto-Parts-R-Us underdash voltmeter indicates the ginny output to be between 16 and 18 volts. Which relay (closest to the battery or farthest away from the battery) do I adjust to cause the cut-out to happen earlier so that the voltage output will be lower?

BTW - 1953 TD LHD

Thanks.

Jud
J K Chapin

I think Jud it depends which regulator you have installed.
( 9 post or 5 post )

There is a good write up in the links above that will help you I think.

Rod


R D Jones

5 post. I just re-read Rick Astley's book and decided it ain't broke so I'm not going to muck with it and change that condition.

Jud
J K Chapin


Some times the generator brushes wear down and instead of the springs continuing to push them against the commutator, the get hung up in the guides.

There should be a cover that you can remove on the generator and check to see if this is so.

I had that happen to me years ago. At that time I just WALKED to the nearest and got some new brushes.
The generator is still running.

Jim B.
JA Benjamin

Many thanks to everyone who has contributed to this. It looks reasonably certain that I'll be off to see a Lucas generator man as soon as I can discover one. The previous auto electrician 4 years ago was a nice guy but from a different generation (no pun intended)so I'll devour and do what I can from these excellent posts, and then if necessary - see the man when I can find him. I won't keep you up to date regularly with the gruesome details but will (eventually) close it off with some kind of resolution.

Thanks again, and in the meantime I have some excellent data with which to progress. It's amazing to see how powerful the internet is - real Lucas manuals! Thanks Lonnie.
John H
John Hoey

John, FYI see http://www.ttalk.info/Holcombe.htm for a bit of generator info. Bud
Bud Krueger

Thanks Bud, very intersting. I haven't had time to start the diagnostic process yet but should get some this week. The generator was new about 4 years ago, has about 2500 miles on it now and, externally, is a Lucas look alike. Internals, those I can see at present, look very similar if not identical. There's about 3/4 inch play in the fan belt, seems OK, but I did notice the field terminal has a bit of play in it. You can wobble it a few mm - is this normal? Just seems a bit odd to me. Anyway, when I go through the well documented testing process I should have a better handle on the size of the problem. I haven't had a chance yet to listen for scraping either so it is very early days.
John
John Hoey

John,

A quick test to see if the problem is the Generator or the Regulator is as follows:
1. On the back of the generator, disconnect both the large (Yellow) wire from the “D” terminal and the smaller (Yellow/Green) wire from the “F” terminal
2. Using a short jumper wire, temporally connect the “D” and “F” terminals together.
3. If Negative ground, connect the red lead of your multi-meter to your temporary jumper and the Black lead to a good ground.
4. If Positive ground, connect the Black lead of your multi-meter to your temporary jumper and the Red lead to a good ground.
5. Start the engine and let it idle, If the generator is in working order, you should see rising voltage as you raise the engine RPM (15-20V!). If so, the generator is good and your problem is the Regulator.
6. If you do not see rising voltage as you raise the RPM, your problem is the Genny!

Good Luck! Terry

A Peddicord

Increase engine speed slowly and carefully. Do not let voltage exceed 20v lest Ginny damage will happen.

Jud
J K Chapin

Thanks everybody, I had some spare time today so I did the checks that I thought would be quickest:

Disconnected gen leads connected voltmeter to D terminal and earth started engine, got about 2 volts fairly constant up to 2000 rpm

Connected D and F together, gradually increased revs and saw voltage increase to about 15v at about 2200rpm, then backed off as I didn't know how well the meter was calibrated and didn't want to do damage

A bit puzzled now, went back to measure resistance at Field Coil Terminal and found it was all over the place. The terminal moves around quite a bit. I first used a very cheap digital multimeter, so swapped for a much bigger and (maybe) slightly better analog, also swapped to alligator clips in case my finger pressure was clouding readings. Very gentle pressure on the clip sent the needle swinging. In certain positions I could get the ideal reading of 6ohm, in others the bad one of 3 ohm, and plenty of others above and below these depending on alignment of terminal with pressure. It was still variable with the alligator clip connection. So it seems there's more to follow up at this point - ie methinks (in ignorance, but by inspection) the terminal should be fairly well secured and not flopping around. So that's where I'll be looking.

thanks again for all the great advice given so far from all. Very much appreciated.

The regulator is one from the great bloke (the late) Bob Jeffers and has been working very well, and when I replaced Bob's with the old coil regulator as a test there was no difference in charging capability. When this is all over I might open another thread and see if the old coil reg can be identified as it doesn't match any drawings I've seen even though it is in the 'Lucas' black box, 5 terminals etc. I have some pics.
John Hoey

John, I had a problem with my system when I got my regulator from Bob Jeffers. He had me do that 3 ohm vs. 6 ohm test. I read 3 ohms. He said that the one of the generator through bolts was shorting against one of the coils. Sure enough, he was right. A bit of jiggling and a piece of shrink tubing over the bolt made all well again. Except that I had blown Bob's circuit board. He very graciously sent me a replacement. The field terminal is a two nut device (no joking). It needs to be secured before attaching any wires. Bud
Bud Krueger

Thanks Bud, that's quite similar in some respects to my situation. Bob was just so helpful to me when I had a few problems of my own making that I hold him in great respect as a fellow. It was only when I started this particular quest that I discovered he was sadly no longer with us.

The only question (at present) is - what is the 'through bolt' ?

That's a great description of the field terminal, by the way.

John
John Hoey

They are the two bolts (or screws) that go though the case from one end to the other to hold the generator together.


Bud Krueger

Thanks again Bud. Looks like it's now timely to remove the car from the generator! I'll try and fix the field terminal first and shrink tube the bolts after that. There will now be a long pause.....John
John Hoey

Not so long a pause! Got more time today and removed generator. I tried to photograph the field coil terminal connection to the yoke but they are not so clear. Suffice to say it looks terrible and it's a bit hard (for me) to describe the type of union. It looks like soft metal hammered, but don't take that as read. Suffice to say that if I can move this connection 5 to 8mm along the length of the pin going into the yoke and get wildly fluctuating multimeter readings then it seem logically the place to start work . Photo to follow.
John Hoey

Photo attached


John Hoey

Well there's the problem; your genny is suffering from Land Rovers!
OK John, tell us about the Landie, you know I have a soft spot for models.

Cheers,
Matthew.
M Magilton

Hi Matthew

It's a big generator, isn't it.
When I was a kid I fell in love with Willys Jeeps. When I got my license and, (a bit later) - a job, I bought a car. All my friends were buying high performance chick magnet luxury vehicles like second hand Morris Majors, Ford Prefects, and the like, but (in 1964) I bought a 1958 SWB Land Rover Hardtop as I couldn't find a suitable Jeep. This was the era when 4 wheel driving was virtually unheard of. I had just about the most fun you can have in that sort of vehicle. Taking ladies to formal events when they were dressed in ankle length skin tight dresses let you get quite close and personal hoisting them up the big step. The passenger's metal floor was heated by the exhaust, only a few mm from it, so often they just put their feet in the dash tray. Too many other stories to bore people with here - like the time a friend drove it up Mount Buffalo in low ratio with the hand brake on.

Top speed of 50mph meant it took quite a while to get anywhere, and I then moved to Sydney where the interesting off road drives were many miles away. Sydney suburban driving was much more demanding than Melbourne so I sold it.

Anyway, fortyish years later, I realised that the smart blokes who'd done so well in 1964 were driving TFs and As, so I belatedly bought the TF. Not much has changed - except now it's my feet that get hot in summer.

Good to hear from you

John
John Hoey

This thread was discussed between 18/04/2014 and 30/04/2014

MG TD TF 1500 index

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