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MG MGA - Negative earth and alternator

I've been reading up on converting to -ve earth and fitting an alternator.

Prices for ready made kits vary from 110 up to 500 pounds depending on the type of alternator. The higher priced items are advertised as 'alternators in a generator body'.

Has anybody gone down this path and what were your experiences?

cheers

Brad C
B Cronk

You dont need to spend so much as that Brad, the only parts you need are the alternator and a new mounting bracket.

I have just seen brand new 17ACR and 18ACR Lucas alternators on ebay for £50 and also the special bracket you need to mount the alternator (as used on a mini A-series engine) also on ebay for £5.00.

They are really easy to fit especially if you follow Barneys instructions on the MGAGURU website. The wiring up is really simple, even I managed it.

You need to convert to negative earth at the battery but that is really the only thing you have to change.

If you need any help with the wiring, let me know and I can email you some info.

Colyn
Colyn Firth

Brad

I was going to say much the same as Colyn and then he posted before I started typing.

It's an easy conversion with the B-Series 1800 engine which has the bracket holes for both the longer generator and shorter alternator. The 1500 engine only has the generator bracket holes hence the need for an elongated bracket or some similar jury strut arrangement.

Colyn mentioned Barney's write-up, which I also used. Moss also have instructions in a PDF: http://www.mossmotors.com/graphics/products/PDF/130-078MGA.pdf

Steve
Steve Gyles

Brad,

just stay away from those expensive fake dynamos/alternators. They are scrap.

Siggi
Siggi

The rear bracket that you need for the alternator conversion is the same part that was used on the late Midgets which were alternator equipped. It is readily available. The Moss part number is 130-115.
Keith Lowman

I was having perpetual flat battery problems up to a year ago . I fitted an 18 ACR and bracket., reset to neg earth and ever since...first time,every time!
Neil Ferguson

Some generator issues are actually problems with the voltage regulator. Not the most reliable of devices. Fitting an electronic regulator seems to have fixed my charging problem and banished some other gremlins. The headlights no longer noticeably dim at idle. Going on three years now without any issues.

I went with the electronic conversion suggested on Barney's site, http://mgaguru.com/mgtech/electric/et232.htm . Find a non-working voltage regulator for the $80 conversion.

Keeps the appearance of original and is a easier fix than trying to sort out the wiring for an alternator. Of course it does not increase the output of the generator, only the alternator swap will do that trick.

John
jbackman

I followed Barney's instructions and did it with no problems, and used the Midget rear bracket as mentioned above. Except I used a Denso alternator, supposedly the "worlds smallest alternator". They are used in Toyota lift trucks and are universally available. I run the same alternator (55 amp) in my '74 Midget and '59 A. I bought both alternators at a local alternator repair shop. Apparently, most alternator shops keep these Denso alternators in stock. They are easily converted to one wire operation, if desired.

--Jack
JM Morris

Jack-
You gotta number for dat Denso? Or summat that would help in searches for it other than a "competent" alt shop, them bein' endangered or extincted.

FRM
FR Millmore

Woohoo! Just won me the bracket I need for the alternator conversion on ebay. A couple of pounds well spent.

Now for the alternator........
B Cronk

FRM: There are no numbers on the Denso alternators I have. I've spent a couple of hours on the internet looking at Denso alternators and have been overwhelmed with the choices and models. No luck. Further, the ones on the internet in my amp range are 50 or 60 amp models whereas I was told mine are 55 amps (and I saw the output on the shops testing rig when I bought them--55 amps).

When I walked in the door at the shop, I carried my Lucas alternator with me and told them I wanted something else that would replace what I had. The owner took one look at it and said "I've got just what you need. All the street rod boys are running it." Thus started my love affair with the Denso.

If anyone is wondering why I dumped the Lucas, it comes down to one thing: I got SICK of replacing alternators or the regulators in them. The problem is the spade connectors (in my opinion). If they ever get too hot, as apparently mine did, the female connectors lose their spring tension and no longer clamp with sufficient pressure to prevent high resistance--and heat. The larger female spade connector is not available locally so has to be ordered from MG specialists. The Denso solves that problem with a screw post.

Not all is absolutely perfect with the Denso. The hot post is on the bottom side of the alternator. When you loosen the alternator and allow it to drop down, the post may accidentally touch the motor mount (ask me how I know) with a shower of sparks. The post is about 1 inch long. That much length is not needed, so I cut about half of it off. No more interference. As a further precaution, I installed a right angle spark plug boot over the wires and post. No more accidents. It would be nice if the hot post were on the back of the alternator.

Nuts and bolts on the Denso are Metric. Minor irritation.

I had to cut about 1/2 off of the backside of the top front ear to get the pulleys to line up.

I did buy an aftermarket alternator bracket (per Barney) which had to be cut in half. About 10-15 bucks. Easy--soft steel, almost like pot metal.

Not all is perfect with the Midget bracket either. The right angle on the bracket is not 90 degrees. It's more like 86 or 87 (on the ones I got). Rather than risk trying to bend the ear slightly further (it's something like 1/4 inch steel) I ground the face of the ear to attempt to bring it to 90 degrees. Still plenty strong with a little material missing.

I'll try to get a picture up in the next few days. The Midget has been running for about 5 years with no problems and the A for about 3 years with no problems. I'm glad to have Lucas behind me.

--Jack

JM Morris

Jack-
Thanks. Have had the Midget bracket problem too - the repo guys don't have a clue. Vise, hammer. OE ones are perfect.
I screw rubber tubing over any "hot" studs. If you waylay a telephone repair guy, they have zillions of cool rubber covers with a big base that has a cutaway for the wire exit.
If you haven't done it, put a solid earth directly off the alt case - I've found all sorts of trouble due to alts not being earthed correctly. Rebuilts especially, and "restored" parts, often have layers of lacquer or paint isolating the regulators from earth.


FRM
FR Millmore

FRM--regarding the solid earth off the case--have done it. The Denso has a small metric screw on the topside, middle, of the alternator I assume just for that purpose. Anyway that's what I used it for.

--Jack
JM Morris

This thread was discussed between 10/02/2013 and 18/02/2013

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