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MG MGB Technical - Bosch Alt. Problem

This question is to Bob Munch or anyone else that has done the conversion to the 55 amp Bosch Alternator.

I just changed over about a week ago from the original Lucas alt. as with halogen headlights and taillights as well as a high performance stereo, I was having a little trouble with the low output on the Lucas.

I did the conversion and everything was peachy til yesterday. Cranked it up in the morning and the little red light lit up on the dash ('69 roadster) and sure enough, the alt wasn't charging. The car started and ran but was running off the battery. Checked all my plugs, double #10 wire to the solinoid, brown/yellow to the third plug and sm. brown wire to the + terminal. Here's my question, Bob mentions that the sm. brown wire is redundant and that it could either be hooked up to the + or left unplugged. I decided to go ahead and plug it in. Bob if you're listening would that hurt the alt. in anyway? or is it just my dumb luck in getting a bad alt?

Took it back to the store and they say it'll be til' Tuesday before they can get a replacement for me. And yes, they checked it out, thought the guy at the parts counter said if I didn't plug up to the + plug the machine said that the alt. was charging. Just to check it out I reinstalled it (since I still have it) without the sm. brown wire plugged to the + and it still doesn't charge.

Oh well, looks like I'm waiting til tuesday.

Luis
Luis

Luis,

I went through two Bosch alternators before i finally gave up and switched to a Delco. The bosch units I purchased and returned and returned were poorly rebuilt

rn
RN Lipow

Thats probably the case as it looked great but failed a few weeks later. As its also a popular upgrade it may just be that the last Bosch alts out there are just garbage. Seems like they are getting harder to find.

I'll try another and if it goes again I may take it to a local rebuilder I trust.


Maybe I should go to the junkyard, get one cheap and have it rebuilt?

Luis
Luis

During my conversion I had to try and try again to get my local rebuilder to set things right.

He was friendly and accomodating, but it took a lot of insistence to get him to test the Bosch alt he
sold me fully and thoroughly and at revs from 600-1500+ rpm. Turned out the alt wasn't charging
below 1200 rpm. After finding the fault, he corrected everything and all has been fine since.

In retrospect...

My local Trak Auto and Pep Boys do not stock the Bosch alt on their shelves - but they can special
order them and have one in 2 days. Although the initial cost of their alternators are about $10 more
than what I paid for my unit - their rebuilders (contract) seem to be more thorough and use a higher
percentage of new parts during the remanufacturing process and their warranty policies are more
robust.

If your alt does not have the external (square shaped) capacitor plugged on the back of it - then the
thinner brown wire gets plugged into the small + terminal, in it's place.

If the square-shaped capacitor is there and plugged into the + terminal, then the thin brown wire is
not needed and should be taped back.

If you contact me directly, I can send you a diagram of this.


Daniel Wong

Send me a copy of your drawing too, Dan. I would also like to know more about this square shaped capacitor. If one end is connected to the square + terminal, then is there another end to be terminated (usually true with a capacitor) and where is that termination fixed? Ground?? Think I will check with a Bosch dealer on that item too.

I did not have to install the small brown wire on my 68 to get it to charge correctly. And this was done on two MGs - a B and an A.

I could say that many people have had trouble with the rebuilt bosch units, and that would be true. However, I could also have to say that I have been told of any number of other brands of rebuilt alternators that have been poorly done as well. I had one electrical parts house guy tell me that the GM, tho usually dependable, was also simply the cheapest to rebuild and replace when they failed for the rebuilders. The GM Delco guys can weigh in on that one.

I think, as I have said before, that it pays to check around for quality rebuilder as there are many who apparently don't care what they turn loose on the public. Keep your receipts, and get one with a warranty regardless. Consistency in performance and reputation is worth something - probably trust. JMO
Bob Muenchausen

Bosch alternators as used on the Ford Fiesta are available from these folks. They are wonderful to deal with.

http://autoexpress.safeshopper.com/

.
Charles Edwards

What is the purpose of the capacitor, radio suppression? If so, will the standard Lucas blue suppression capacitors work in its place?

Cheers,
Paul Kile
Paul Kile

I'll take a look at the new one when it comes in Tuesday, :(

I think this time I'll tape back the brown wire and see how it functions.

Hopefully this one will be rebuilt a little better.
Thanks Bob and Dan. I keep all my reciepts so I can cry later when I total up what the resto costs are. I also keep them away from my wife. What she don't know won't hurt me.

Luis
Luis

Thanks to both Charles Edwards and Danny Wong for your info. Danny's "drawing" is excellent and clearly shows what to do. And we can always use a good source of Bosch (and other) alternators.
Bob Muenchausen

Bob M. and Daniel Wong,
Will you be uploading Daniel's diagram to your website? I have one of those Bosch Ford Fiesta alternators ready to be installed on my MG 1100, which is still undergoing restoration. I would like to resolve the capacitor issue before firing it up.

Thanks,
Paul Kile
Paul Kile

I am just about to install a Bosch in my 73B. I went to Bob Muenchausen's AOL page and, gasp!, there is nothing there! Bob, have you taken your information page out? Help!
Gary Elmenthaler

I might have been working on it, Gary. I just added Danny's excellent graphic of the wiring and the back of the unit to that site (big thank you, Danny!!! :-) ). For anyone else who is interested, pls. go to http://hometown.aol.com/idbritcars/boschAlt.html for the Bosch conversion page mentioned above. Thanks one and all for your interest in this conversion. There are links to other interesting MG electrical sites there and for the AC Delco Alt. conversion site too.
Bob Muenchausen

http://autoexpress.safeshopper.com/

Damn! $44.95 for a Bosche alt for a 1980 Fiesta? Thats a super good price!
gerry masterman

No offense, but now the question will be, is it a super good alternator. Anyone who has bought theirs from these folks should be a worthy testimonial - was that you, Charles? ;-) Thanks for the link!!!

Paul:
An empirical answer to this question on the wiring of the alternator.

What Dan shows is correct IF you have and intend to use the noise suppressor shown in his diagram. However, if you are NOT going to use the noise suppressor, it is equally correct to not NEED to hook up the small brown wire to the smaller + terminal.

I have been running my Bosch unit without the suppressor or the small brown wire connected to that + terminal for over two years now with no problems with charging or current output. I am still on the same battery I had when I installed this conversion, and it works as faithfully as the alternator. I have also installed this conversion on my old MGA, again in the same manner with no problems, and the email correspondence I have received from grateful owners with a positive experience after having wired the Bosch unit up WITHOUT connecting the small brown wire has outweighed those with problems of any sort about 10 to 1.

Problems, BTW, seem to end up most often being a problem with indifferent rebuilding by some rebuilders, a lemon alternator, or, unfortunately, the penchant some folks have for not asking questions or studying up on what they are doing before moving ahead. That said, I think it is obvious to most practicioners that an understanding of what they must do beforehand was key to their success.

That is a good question, Paul, and you are not the first to ask it. It is a good thing to post this info on this BBS for those, like yourself, who care and wonder what is correct. Nobody likes to see their $45 - $95 alternator go up in smoke, nor their wiring harness. Ask me, I had a Lucas Generator present me with that little gift once upon a time.
Bob Muenchausen

Bob, Thanks again for the response on whether I did the conversion right.It works fine.
Paul

Bob, I've been using a Bosch on my '77 B since 1988. I've replaced the regulator with one from NAPA in 1992, but the Bosch has been reliable. I removed it from a Fiesta that I had rebuilt and turned into a rally car. The body metal in the Fiesta was quite thin and it began to dissolve into a brown powder, so I had to sell it. Late last year I purchased a Bosch from Autoexpress via the internet and received it in just a few days. The alternator was clean, complete with pulley and seemed ready to go. I didn't notice that the alternator was the mirror image of the one I needed until a week later. Autoexpress was very quick to send me pictures of the various Bosch units they had. I selected the one I needed and they sent it prepaid via UPS and had UPS pick up the incorrect unit. Mistakes are inevitable. It's how you correct them that leaves an impression. My impression of them is quite good.
Charles Edwards

Bob,

I think you're right. I've just installed the new alt. and so far so good. I left out the sm. brown wire this time.

I love having the ability to run my headlights, radio, brake lights and turning signals all at one time.

I purchased the alt originally at a local Discount Auto Parts store and they did honor the warrenty. It cost $79.95 + tax (6.5%). Luckily kept the receipt and box.

The alt had to be special ordered so took a couple of days. It seems there may not be too many of these things laying around.

If it goes out again, I'll take it to a professional rebuilder I'm aquainted with locally. He rebuilt my old Lucas which lasted 10 years (and was still working when I sold the car) for about $25.

Thanks again for the assistance.

Luis
Luis

Thanks, Charles and Luis! You are certainly right that how a problem is handled makes a big difference and leaves a lasting impression. Just look at some of the supplier Trashings on this BBS for proof of that. It is good to have real experiences to help us judge the places to seek out first.

And thanks too for the feedback on your problem, Luis. As Dan has said, it is most helpful to all of us to know what finally did work for any of the problems we try to help folks with. Often, it is that feedback that clarifies the original situation or makes us all aware of some unanticipated cure or problem which can help us all assist those who come here looking for the best knowledge and best methods of finding and performing cures. I have a suspicion that even the pros who visit this site learn something new to their experience. We certainly benefit from their expanded experiences too.
Bob Muenchausen

As a suggestion for the smaller brown that is not to be connected, use a "spare wire cap". I work for Hi-Line Inc. and we sell maintenance supplies to the aviation and avionics industry. These are used in avionics when one radio is removed and another put in its place , possibly with an extra wire. They just cap it off for use the next time. These crimp on just like any other terminal. These should be available from any electrical shop.
Gary Elmenthaler

This thread was discussed between 20/04/2002 and 24/04/2002

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