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MG MG Y Type - Regulator Problems! Help!

Hello all. I am taking UMG 662 to Goodwood tomorrow for the GRRC car display. Earlier this week I noticed that, after some rather sporty driving on the Brooklands Double 12, the ammeter was showing a greatly increased charge (at high revs nearly off the scale). The fan belt was not too tight and the dynamo seemed fine so I suspected a fault in the regulator. I got a new one from NTG and fitted it this afternoon but it was defective (Chinese rubbish) so I transferred the regulator from UHK 111. That is showing the same problem - i.e. over charging. It had been working fine on UHK so I am beginning to wonder whether the ammeter is faulty - but what could go wrong with that to show such a high charge? Alternatively could it be the dynamo? Need to set off tomorrow at 9am so all help gratefully received! Thanks, Marc
Marc Hanson

Does the charge rate drop back if you switch on the headlights ?.

You can adjust the regulator charge rate yourself - no special tools required and it's all spelt out in the workshop manual.

Does the ammeter return to 0 when you switch off ?.

Get out the manual & have a go.

Tony

PS - I am not an auto electrician, so my advice is only from experience.
A L SLATTERY

Thanks Tony. Find it hard to believe its the regulator at fault - one maybe but not two. Yes charge falls back slightly when lights et al on and ammeter returns to zero when off. If its the dynamo delivering too much charge will slackening off the fan belt help? Marc
Marc Hanson

The generator will always deliver too much charge - it's the job of the regulator to control the charge based on the load.

They are a pair & the regulator needs to be adjusted to suit the generator that is delivering the charge.

The generator in UHK111 may be charging less, or it has a different size pulley on the generator. Race prepped saloon cars often had larger pulleys to slow the generators at race revs, so as not to "over speed" the armature/bearings.

Check out the manual - you can do it !.

Tony
A L SLATTERY

I think its odd that the ammeter suddenly started showing a high charge on UMG. It was not a gradual build up of the problem. That says to me something has become defective. The most obvious culprit was the regulator. UHKs regulator was fine but when swapped into UMG produces the same overcharging result. So it appears to me that either the ammeter is faulty (but not sure how that could be)or something else has happened that has led to overcharging that the regulator cannot deal with. So not sure adjusting the regulator is the answer.
Marc Hanson

ps At idle the ammeter is showing in between 0 and the first negative mark which it never used to do)but the red noncharge light is not coming on (it does when ignition is on and engine not running) and when on charge at 2000 revs is showing at the mark in between 0 and 30 but wildly fluctuating all over the place. So I guess it could be the ammeter?

pps my workshop manual has nothing on adjusting the regulator. It just says send it back to Lucas!
Marc Hanson

All you need to know you will find on the IMGYTR Website -> Technical Centre -> Technical Data -> Generator charging Control.

Here is the link:- http://www.mg-cars.org.uk/imgytr/pdf/lucascourse5.pdf

I understand you don't have time for the learning curve, but unless you can find an old skool auto sparky you are going to have to fix it yourself.

Good Luck

Tony
A L SLATTERY

looks like ammeter issue rather than regulator - which is a relief..
Marc Hanson

I'm a bit late to help Marc but I just wonder if there is a short circuit on the dynamo between the field and armature ie perhaps there is a loose connection on the studs and the connecters are touching, or if the car still has the original wiring an insulation fault. Something seems to be giving the dynamo full output. Try switching the wind screen wipers on and then start the engine, if its high dynamo output they will certainly greatly speed up. Bryan
B Mellem

Good tip Bryan. They didn't sped up at all. Wish I had thought about that before spending hours swapping round regulators!
Marc Hanson

Its handy to get a cheap multimeter The volts across the battery during charging is about 13.5 volts if the regulator is overcharging this could rise to over 15 volts which will cook the battery. Bryan
B Mellem

By the way I purchased a replacement regulator and found the charge rates way out, I settled for a rough and ready method of setting by switching on the head lights then setting the revs to 2000 [approx. 30 mph speed] and adjusting the regulator to just a needles width + side on the ammeter, clearly you need a working ammeter and a battery in good condition.
B Mellem

This thread was discussed between 05/08/2017 and 10/08/2017

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