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MG TD TF 1500 - Generator to Alternator

Once again I come seeking sage advice.

My '51 TD is a positive ground. It has a positive ground Pretonix (sp) ignition, and a modified Lucas fuel pump with an electronic control marked (positive ground". The voltage regulator has been transistorized.

My question is this. The generator is shot as confirmed by a local rebuilder. I have a replacement backordered through Moss. They say it will be shipped at the end of January.

I have found a source for a Delco 100 amp alternator with a tach drive ($350). I could cancel the back order and go with the alternator, but what about the other positive ground parts? ignition, and fuel pump. I realize that the voltage regulator would go away.

Am I better off just replacing the generator, or attempting the conversion? The alternator is through British Auto Electric in Anaheim, Ca.

Thank you for your help.

Bob
Bob McLeod TD 5618

The pertronix will have to be changed for a negative ground unit. Dave may be able to help you salvage the fuel pump.
L E D LaVerne

Bob - You might be able to switch the leads of the Pertronix and get away with it - it is probably worth trying it before purchasing a new one. I can reverse the polarity on the fuel pump. Cheers - Dave
DW DuBois

There is no way that you will ever need 100Amp on one of these cars. Affordable alternators are available in negative or positive earth versions with a tacho output and even in a dynamo case. 45 Amp is penty.
Dave H
Dave Hill

Sorry, but the Pertronix can't just have the cables swapped. If you insist on sticking with a positive ground system, why not get a positive ground alternator?
Bud
Bud Krueger

Bud that would be my choice if I could find a positive ground alternator with a tach drive. Any ideas where?

Bob
Bob McLeod TD 5618

Check the size of the Delco unit. I have fitted an alternator from a Renault Clio and found that many from other cars were too big to fit the TFs engine bay. I think there is more room with a TD. If I was to start again I would buy a tacho drive alternator from the Octagon Club. They are just over £100 and can be ordered with either positive or negative ground.

Jan T


J Targosz

I would advise continuing to use a generator. I have my doubts you will find an alternator to be reliable.
Be well, David
D. Sander

David Sanders, I think I'll take your advice. It is the easiest, most cost effective solution. Thanks everyone for your input.

Bob
Bob McLeod TD 5618

This may be a viable conversion item worth further investigation...

http://www.qualitypowerauto.com/item_135/Positive-Ground-12-Volt-Alternator.htm



T.A. Sirp

That does not appear to have a tacho drive ability?

I see the MG Octagon Club unit is 135punds, less VAT plus shipping, does incorporate the tacho drive and looks like a generator.

Peter
P G Gilvarry

I am using the same type as sold by MG Octagon and it is working very well so far. I have had it for about 12months.
Dave H
Dave Hill

That MG Octagon Club alternator (SEL045D Stealth Dynamator [45 amp Alternator] with Tacho Drive Positive Earth TD/TF/YB) appears to be a very prudent upgrade.

Today is the first time I've ever seen it or perused the Club website. If facing a need for generator replacement, I would definitely consider it as a choice alternative.






T.A. Sirp

There ia also a Negative Earth version, which is what I am using.
Dave H
Dave Hill

The generator has more than enough power for a stock T-Series, even with a couple accessories. It's also more reliable and cheaper to rebuild.
Steve Simmons


" would advise continuing to use a generator. I have my doubts you will find an alternator to be reliable.
Be well, David"


On what basis would an altinator be less reliable, please.

Jim B.
JA Benjamin

Some of the alternator conversions have a problem with overheating and burning out. The stock generator is able to handle the electrical load, and is both reliable and easy to maintain.
Be well,
David
D. Sander

David d is correct - most of the alternators that are made to look like generators have issues with heat soak and premature failure has been reported as a common issue. The reason is simple - alternators produce a lot of heat, and that's why they always have a lightweight alloy case with tons of slots for ventilation. When you try to put that same thing inside a thick, poorly ventilated tubular housing you get heat soak issues and subsequent electronic failure.
Kevin McLemore

We are somewhat going back to the Tesla vs. Edison argument of ac vs. dc. But, the big difference is that our cars won't run on ac. The automotive alternators could actually be very efficient, low maintenance, devices except for that pack of diodes that have to convert the ac to the 12 volts (or 6) of dc. That diode pack generates a lot of heat and is quite an expensive part of the automotive alternator. The multiple segments of the dynamo's commutator do that same conversion job with much more efficiency. Bud
Bud Krueger

Yes, its an absolutely fair question. Well engineered alternators should be more reliable than dynamos / generators, and indeed they are in modern cars. However when you put an alternator in a solid aluminium sleeve to make it look like a dynamo, it seems that some alternators can fail. Strangely, all of the failures that seem to have been mentioned to date, appear to be with the earlier and more expensive type, rather than the more recently available inexpensive type. Whether its just a matter of time, is not known. Indeed, some of those expensive alternators failed very quickly. All I can say as an MG Octagon Club member is that I haven't seen a single report of a failure with the later type yet, and they must have sold many of them. In my case I fitted a 7 blade MGB type fan to help with cooling in the engine compartment.
Dave H
Dave Hill

This thread was discussed between 06/01/2017 and 08/01/2017

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