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MG MGA - Generator problem

A few months back I had an 1800 engine and a 5 speed tranny installed in my MGA. When I was driving it in for the 500 mile valve check and oil change, the car died. Unfortunately, I was going over Mt. Hood in Oregon, in a pouring rain and still about 70 miles from my destination. (bummer) The problem turned out to be that the generator crapped out.

Now the shop tells me that they cannot make the generator work correctly with the car. They want to convert to an alternator and have the tach rebuilt to be electronic. (I hope I have that right) I'm not a mechanic AT ALL and I am totally baffled as to what the issue might be. It was working with a generator and now it won't?

Has anyone out there had a similar problem? I know I'm not giving a lot of information but I don't have a lot. All I know is that the car was running and performing beautifully with the generator. The tach and speedometer were spot on. I drove it over the 500 mile mark with no issues whatsoever and I don't want to pay to have the tach converted.

Any ideas as to what might be looked at would be appreciated. I have it at a very reputable shop that I've gone to for many years. But they're mostly an older American muscle shop. (took my '64 GTO there for many years) Maybe there's something they're overlooking that they're just not familiar with. ??

Thanks,
Pat
Pat10

Test the generator first. Jumper wire the F and D terminals together, and connect a volt meter from "D" to ground. Run engine and check voltage. Voltage should increase with engine speed, and should make 16 volts by 2500 rpm. Do not run it past 20 volts. If it can make 16 volts, the generator is okay. If not, you can buy a replacement generator, or you can have the old one rebuilt.

When you can verify the generator is working, then you MUST check function of the control box. If a $40 control box fails it can wipe out a $100 generator.

Connect voltmeter from generator "D" terminal to ground, run engine,and monitor voltage. Voltage should increase with engine speed. When it reaches about 15 volts, the voltage should stop rising and stay around 15 volts with increasing engine speed.

If it does not make increasing voltage,then the regulator is duff. If it does make increasing voltage but it stops short of 15 volts, then the regulator relay may be adjusted to the correct range. If it goes radically beyond 16 volts, then the regulator relay is probably toast, and you need to replace the control box.

Installing an alternator is a matter of personal choice, not a requirement. Tachometer has nothing to do with the generator or alternator. If the mechanical tachometer has failed it can be repaired.
Barney Gaylord

"Tachometer has nothing to do with the generator or alternator."

It does with a 1800 MGB engine that doesn't have the tach drive capabilities on the rear end of the camshaft. It would appear that Pat may well be using a generator out of the T series cars that have the ability to drive a mechanical tach.

Pat - I would suggest that you take the generator to an auto electric shop in your area and have the generator looked at. The early MG generators are not that sophisticated and are quite easily fixed. Do the tests that Barney suggests and then take it from there. Cheers - Dave
D W DuBois

You can have the best of both worlds and fit the new Accuspark alternator that is in a dynamo-like casing. It is much cheaper than the Dynaspark alternative, and seems to be a well made piece as I have one on the bench at the moment.

http://www.accuspark.co.uk/dynamator.htm
dominic clancy

Perhaps I'm missing something, but I would question the competency of the shop you're using if they can't repair a generator. It's one of the easiest components on the car to service. Assuming the armature is good, and they almost always are, it's a 20 minute rebuild on the bench with $15 worth of parts.
Steve S

Had a generator rebuilt a few months ago with new bearings and bushes etc. Cost was Cdn$100.
Any good auto electrical shop should be able to do this.
Tach drive is by a cable from the engine if an early B motor, or electrical from the coil if later B engine.
Peter.
P. Tilbury

My generator rebuild was also a relatively simple replacement of bushings and brushes, but when you open one up, there's always a good chance that the commutator will need to be turned on a lathe, and the insulators undercut. From the point of view of a repair shop, it's bad form to have the cost of a job come in at some multiple of the initial estimate due to the addition of machine time. Given the low cost of a new generator these days and the cost of labor, rebuilding doesn't make a whole lot of sense compared to just replacing with a new unit, at least in a commercial shop environment.

Upselling him to an alternator conversion is maybe a little excessive, but it's undoubtedly the most trouble free option from the standpoint of continued maintenance.

I suspect that Dave is correct, and some DPO used one of the generators with a tach drive as a workaround for keeping the mechanical tach with the MGB engine. If that's the case, either the existing generator will have to be rebuilt, or conversion to an electric tach will need to take place.

-Del
D Rawlins

I'm a bit bummed. Let me start from the beginning for those that don't want to read the whole thread.

I had an 1800 engine and a 5 speed conversion kit installed in my '58 coupe. Everything was wonderful. Love it! When I was taking it back to the shop for the 500 mile oil change and valve adjustment (150 mile drive) the car just quit running after about 70 miles. The problem turned out to be the generator.

After 2 1/2 weeks in the shop, a rebuild on the generator (made noise afterward) and an install of 2nd used rebuilt generator, I ended up getting the car back with an alternator installed and a non-working tach. Explanations from the shop just kind of went over my head. (intended, I think) They said they still are planning on getting it right but I don't want to take it back again.

I'd like to get my tachometer working but I'll take care of it myself (as far as removing, re-installing) if someone can tell me what needs to be done. I am assuming this is something that one of the experts out here can tell me without having to see the car. And I'm hoping it is something that a handy person (me) with no real mechanical experience (or special tools) can handle.

The 5 speed was the unit from Moss Motors if that helps at all. I don't know or think the engine type makes a difference. ? If it does, I can get that and any other information that might be needed.

Thanks!
Pat
Pat10

We don't have enough information about the car to offer much help. Is your current tach mechanical or electric? If mechanical, is it hooked up at all, was it hooked up to a drive on the engine, or the back of the generator? Is the 1800 engine a 5 main unit, or is it a 3 main unit that actually does have a tach drive?

If the tach has been changed to electric, what kind of tach is it?

It doesn't really matter at this point, but I would be interested in knowing if the first generator that "failed" was the one that was with your car before the engine swap, or if it came from someplace else.

Is the alternator that is currently installed working properly?
D Rawlins

5 speed would have nothing to do with the generator/tach problem. Find yourself another shop..... period.

Generators are an easy fix for auto electric places, and should not make noise after.

tach is another issue. It is either mechanical (runs off a cable like a speedo cable) or its electrical.

You need to find a knowledgeable shop, and ask a lot of questions here. Photo's are good. A non working tach will not affect you driving the car until it is sorted.
C.R. Tyrell

The generator was ordered from Moss Motors and was 'needed' (?) to go with the new 5 main 1800 that was installed. The tach is original with the car, so I'm guessing mechanical. I realize that I don't need it to drive the car. I just want it. It has always worked. And it worked for over 500 miles after the rebuild. When the generator went bad, they could not get it to work again (to charge the system). I don't understand why. They (the auto shop) took it to a very reputable electric shop in Portland, Oregon and it bench tested fine. But once they put it in the car...no luck. I told them when I left the shop 2 weeks ago that I wanted everything working. They said they would have to pull the tach and have it rebuilt to be electronic. They called me back to Portland this last Friday. I assumed all was good. Not so. They put an alternator in the car and left the tach unhooked. Said they would be in touch.

Let me tell you that I've known the owner of this shop for many years. I took my '64 GTO there and never had a complaint. Walking into their shop is like walking into a muscle car dream. But I'm guessing I should not have entrusted them to convert my MGA to an 1800/5 speed configuration.

So, with a 5 main 1800 and an alternator instead of a generator, do I need to have the tach rebuilt to be electronic? Is there something special needed for hooking up?

Sorry...this is like a book. I'll stop now.

Pat10

Pat - "I took my '64 GTO there and never had a complaint" A MGB is a completely different animal from a GTO. I am sure that the shop is perfectly good with domestic cars, but I am with the others, you need to walk away from them and find a good British car shop, There are several in the Portland are alone. Check with Club 'T' MG in Portland at http://www.clubtmg.org/ for a list of shops that they recommend.

"The generator was ordered from Moss Motors and was 'needed' (?) to go with the new 5 main 1800 that was installed" That sounds very much like they put a generator for the T series cars (TD, TF) that has a tach outlet on the back end of it. That would also require a tach gearbox that is geared for the pulley ratio of the crankshaft and the generator to give you an accurate tach reading.

You also need to take the two generators that aren't working to an auto electric shop and have them test them. Generators don't just die for no reason - there is a good chance that the regulator in the car was/is bad.

First and foremost DO NOT TAKE YOUR MGA BACK TO THE SHOP YOU HAVE BEEN GOING TO - they are not British car mechanics and all they have been doing is butchering your car. Cheers - Dave
D W DuBois

This page from Barney should answer all of your tach questions:

http://mgaguru.com/mgtech/dash/dt201.htm

Short answer is your existing tach does not need to be "rebuilt" to be electronic; you need an electric tach from an early 5 main MGB, which will need to be converted to negative ground configuration in order to work with the currently installed alternator.

More information on the conversion to negative ground here:

http://mgaguru.com/mgtech/electric/et202.htm

It would be a good idea to ensure the wires at the coil were switched, since it sounds like the shop you were taking it to is a bit clueless.

As for the alternator, it's too bad they didn't or couldn't troubleshoot the problem with the generators. If you still have the generators (I hope so, because I assume they charged you for them), it would be a good idea to do as Dave suggested and have them tested, because it's entirely likely that the problem was the voltage regulator, and/or one or both of them may only need to have the field flashed (polarized) in order to work. If they are good, you may at least be able to recover some of what you have spent by selling them.

Since your car is already in a non original configuration, I would be inclined to just keep the alternator installed if it is working properly. I wouldn't take it back to the same shop... Sounds like they want to charge you to screw up a perfectly good mechanical tach, and then probably sell you the electric tach you would have ended up buying anyway. And at this point you are just rewarding them for their earlier screw ups.
D Rawlins

Dave, didn't some of the spridgets also have a tach drive on their generator? It may be that he has/had one of those.
D Rawlins

"didn't some of the spridgets also have a tach drive on their generator? It may be that he has/had one of those."

Dell - I believe you are correct now that you mention it. That may be what Moss is supplying for the T series cars (it even has a couple of extra amps output than the older generators for the T series cars. Cheers - Dave
D W DuBois

Thank you to everyone that responded. I believe that what I am going to do is buy an electric tach to go with the 5 main 1800 that was installed. Hopefully that is an easy, straightforward installation job. But I have a question.

How do I tell if my car is negative or positive ground? I didn't convert it but I can't say whether or not someone else before me did.

Thanks,
Pat

P.S. I would like to add that the shop in Portland didn't charge me anything after the initial cost of installing the motor and transmission. They had labor on the original generator, which made noise after the rebuild. They purchased a 2nd one that the electrical shop could not get to work in the car. And, finally, they gave up on a generator and installed a new alternator. I was unhappy about all of it but at least it didn't cost me anything.
Pat10

Look at the battery terminals and see which one goes to ground. The terminals should be marked -/+ on the battery.
John DeWolf

Pat,
Mystified how a generator not charging became a problem with the mechanical tach. You really need to give more information, or talk to your shop as to how this came about.
If the generator was bench tested and found to be working fine, but does not charge when installed in the car, then you may have a problem with the control box. This is mounted on the firewall near the fuse box.
A shop dealing with modern cars, all of which have alternators fitted on the engine, and all alternators have built in regulators, would not know about the control box in an MGA.
As someone has already said - you need a shop that knows MGs.
Peter.
P. Tilbury

Pat - with the alternator installed, you car became negative ground, whether or not you wanted it to be. Positive ground alternators are very rare and very expensive. Follow Johns directions to confirm that the car has been swapped over to negative ground

Peter - If you read the first couple of posts by Pat, he says that the original 1500 engine was swapped out with a 1800, 5 main bearing engine. The 1500 engine has the tach drive off of the back end of the cam shaft, the 1800 5 main bearing engine doesn't have that option. What the shop did was to get a T series or early Midget generator that has a tach drive off the back end of it. Either the regulator was bad or the new generator was bad, thus the flopping and twitching with another generator and ultimately the alternator. Just why no one was able to resolve the generator problems is a mystery to me, but I have said all I am going to say on that subject. Obviously, Pat's car is operational and his purchasing an electric tach to replace the mechanical tach should get him back on the road. Cheers - Dave
D W DuBois

Thank you everyone. I appreciate the responses and good information. I have found a refurbished, electric tach on Ebay that is supposed to be for a 5 main 1800. I guess I'll get that, hook it up and see how it goes.

Thanks again,
Pat
Pat10

Pat,
Note that the electronic tachs came either positive or negative ground. You need the one that suits your car, or have it converted to match your car.
Peter.
P. Tilbury

Thanks Peter. My car is positive ground and I found a refurbished, electric tach with positive ground on Ebay. It's a Smith's, which is a teeny bit disappointing as only my temp gauge was not Jaeger. (I like the 'made in England' thing. It is an English car after all.) But the picture of the Smith's tach looks good so I guess that's ok.
By the way, I found out that the shop that did all the work on my car was able to use my MGA's mechanical tach with the 1800 engine by using an old Bugeye Sprite generator that had a tach drive. I guess that it just could not produce the needed juice to keep the A going.
So, it wasn't that they couldn't make the generator work. They just couldn't get it working as well as it needed to for my car. And, now I have an alternator.
For those that said to walk away from them and find a new shop...they may be a muscle car shop but they're a smart bunch of very experienced mechanics. Experienced enough to know about the Sprite's tach drive generator as being a possible option for my car. (But they still raz me big time for owning a British car, right after they tell me what a sweet ride it is.)

And, for anyone out there that is on the bubble for putting an 1800 with a 5 speed conversion in their MGA...DO IT!!! Wow what a nice difference.

Just don't tell your wife how much you spend on it. I didn't. and that's why I'm still married.








Pat10

Pat - The Smiths tach is also made in England. Being a positive ground tach, it was originally used in the early MGBs. The later MGBs also used a Smiths but they were negative ground and still later were smaller in diameter. Bottom line, it is still British. Cheers - Dave
D W DuBois

You have a positive ground alternator?
D Rawlins

Ahh! Dell brings up a good point, positive ground alternators are very rare. There is a good change that your your car was converted to negative ground when the alternator was installed. Check which terminal of the battery is going to ground. Cheers - Dave
D W DuBois

Oh, I mistakenly thought U.K. said U.S. That's good. But the Jaeger print font looks sooo much cooler. :)

The shop must have found a positive ground alternator. When I called them to ask about buying the tach (to make sure it was the right application), the mechanic told me to make sure that it was positive ground because that's what my car is.

In all this, I didn't mention the one thing that was done that really had me a bit upset.
The new engine...they painted it B.R.G. It looks really nice but I don't believe there is any color but the maroon color that is stock.
So I guess that's one thing they didn't know.




Pat10

Pat

The dial faces of the Jaeger and Smiths are the same size and graduation. It's just the two attachment screw holes are in a different position. Some of the guys here have managed to swap the dial faces over.

Every credit to your shop for lateral thinking and putting on a generator that took the original tacho. I have never heard that mooted before. Like you are now doing I went down the Smiths electronic route and alternator, although I had previously converted to negative earth so found the sourcing of parts a little more straight forward. Swapping to negative earth is very straightforward and Barney covers it well; but as you have already found positive earth parts that is all in hindsight.

Not a major problem to repaint the engine next time you have it out. Something I have done 3 times in the last dozen years. When you get practised at it you can get the engine out in a few hours. Dominic can do it in about an hour. I am closer to 2.5 hours.

Steve
Steve Gyles

I did have a thought about swapping the faces but I think I'll leave as is. I have to send my old one to the supplier. I think he's really getting a pretty sweet deal as he is getting a nice, totally working, mechanical, positive ground tach in exchange for the electric one he is sending me. And he's getting money to boot. But, what the heck, at least I'm getting what I need. It's worth it.

Next time I have the engine out? I'm hoping there won't be a next time but if there is, I'll give you or Dominic a call and you can hop on over here to Oregon and pull it out for me. I'll have a cold, Oregon micro brew ready for you. :) (AFTER the job is done)



Pat10

This thread was discussed between 04/08/2014 and 15/08/2014

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