Generator to Alternator

[MGBloke]

I have a 67 mgb roadster with a 69 transmission. I have reversed the car's ground so that it runs negative earth. I currently have the symptoms of a busted generator. That is, the car runs fine, and keeps itself running, but after about 10 days, i have to recharge the battery with a charger. And if I use the headlights, then the car will eventually sputter and die. i think the generator is providing enough juice to keep it going, but not enough to charge, and not enough to maintain power to the coil and headlights, or any other power sapping accessory. That, and the ignition light stays on all the time, which must mean that the relay switch isn't capping 12 volts, or whatever the number is that should deactivate the relay.

So, i've decided I should replace the generator, but I was thinking. How hard is it to upgrade to an alternator, and would that be a better option? Anybody done this to their B's before. Any second opinions are most welcome.

Thanks.

Joey

 

[tony barnhill]

Alternator is definitley better than generator any day...I'm not an electrical guy so they'
ll have to talk you through that part...however, you'll need some brackets & probably want to redo your oil filter if you still have the old type.

 

[vping]

Couldn't you use later parts and swap them on to the 67? I have a complete 74 at home, I'll ahve to check.

 

[Steve_S]

First things first. Have you tested the system? Generators are fairly bomb-proof devices so don't suspect it just because the battery goes dead. Consult your maintenance manual for the testing procedure of the charging system. The contacts in the control box could be corroded or out of adjustment, you could have a bad connection or ground somewhere, the battery could be bad, or the generator could indeed have a problem.

Everything in the Mark I MGB electrical system is easily serviced, usually with basic hand tools and a multimeter. There are no circuit boards, electronics, etc. The only electronic device in the car is the tachometer.

Regarding replacing the generator with an alternator, it depends on your power needs. The generator chosen by the factory suits the needs of a stock MGB. If it does not, there is a problem somewhere in the system. If you have added accessories which require more than a few additional amps, then you may have need for more power. In this case there are three options.

1. Install a more powerful generator
2. Install a modern alternator
3. Reduce the load on the charging system

Option 3 can be achieved by the use of LED lighting, relays in the lighting system and other tricks using modern electronic parts.

The advantages of an alternator are greater overall power output and more power delivery while at idle. Some people are seriously irritated by the windscreen wipers slowing down at a stop light, so they switch to an alternator. It's funny really, because modern cars do the same thing, only it's called a feature and you pay extra for it!

The advantages of keeping your generator are that it is easily and cheaply rebuilt, and will last a very long time before needing service again. It is also unaffected by polarity changes and power surges (within reason). If you prefer to keep the car original, this would be another advantage. You can also keep a couple tiny parts in the trunk which will allow you to rebuild the generator on the road, which is something the average person can't do with an alternator.

 

[Dave Russell]

I have a 67 mgb roadster with a 69 transmission. I have reversed the car's ground so that it runs negative earth. I currently have the symptoms of a busted generator. Joey

You DID repolarize (flash) the generator field - Yes? I see no mention of it. If not, the generator or cutout may be damaged. I'm sure someone will explain how to do it, if it isn't too late.
D

 

[Steve_S]

Dave points out the obvious that the rest of us failed to think of and he's absolutely right.

See here: https://www.mgnuts.com/mg/tidbits/polarizegen/

 

[vping]

Here are the pics if you can make 'em out.

 

[19_again]

Joey, Jack saved me a bunch of time with this very clear article.In the event you need to reverse polarity, this is the way to go.Instruction on how to polarize a Generator:


In all the years I have been in business, I have heard many versions on how to polarize a generator and voltage regulator. Some versions are correct, others are totally wrong.
Polarization is a procedure which matches the polarity for the generator and the voltage regulator. The majority of the vehicles are manufactured negative ground although some of the older vehicles were manufactured positive ground. The generator has to be set up for either polarity. The generator will charge either way, however the voltage regulator has only one polarity. Whenever the battery is disconnected from the vehicle for any reason the polarization procedure should be performed.
The recommendation on how to polarize a charging system is the following: After the installation of a battery, generator or voltage regulator follow these procedures. The terminals on the voltage regulator are labeled with letters and this is where you will do the polarizing procedure. Both of the components will have battery power so do not start the vehicle or turn on the ignition switch before polarizing them. You will need a small piece of wire fourteen or sixteen gauge with alligator clips on the ends. Find the "B" terminal on the regulator and attach one of the alligator clips, find the "D" terminal and touch the terminal with the other alligator clip. You can touch the terminals a few times and it will produce a soft light spark. Under no circumstances touch the "F" terminal or any other part of the regulator or you could damage the regulator.
For the Lucas voltage regulators that have the teminals labeled A1, A, F, D, E, the polarization procedure is the same however the terminals that will be used are the "D" terminal and either the "A" or "A1" depending on which teminal is used on the vehicle. Either terminal can be used if wires are going to both terminals.
Start the vehicle and you should see the red generator light go off on the instrument panel, you may have to rev the engine up a few RPM, generators have a tendency not to charge at idle speed. If you have a gauge on the instrument panel the gauge will respond accordingly.
Good luck, Mike

 

[MGBloke]

I did reverse polarity on the generator when I switched the ground. It ran and operated fine for about a year and a half, so I'm sure that is not the problem. This is a recent problem.

Steve S's first post is really the answer I needed. Thanks, Steve. Thanks to everybody for your help and opinions. My plan is to run a few tests on the generator and voltage regulator and decide from there.

Thanks, guys!

joey

 

[DrEntropy]

I gotta say I'd rather keep a genny on my stuff than go with an alternator.

Just went thru a real contest getting an alternator for the Alfa that actually ~worked~... with a generator I coulda swapped out th' brushes and been on my way in an hour. Mebbe less if I were certain the bearings were good. Can swap out brushes in one with the genny in-situ with practice. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[tony barnhill]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Just went thru a real contest getting an alternator for the Alfa that actually ~worked~... [/QUOTE]

But, Doc, you're talkin' Eye-talian....we're discussing British....hehehehe

 

[Steve_S]

Same thing! The MGB GT has an Italian-designed body. /bcforum/images/%%GRAEMLIN_URL%%/laugh.gif

 

[tony barnhill]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Same thing! The MGB GT has an Italian-designed body.[/QUOTE]

But, that's about all...hehehehe

 

[Steve_S]

Yeah, but it's all I had. /bcforum/images/%%GRAEMLIN_URL%%/shocked.gif

 

[DrEntropy]

And the eye-tie cars used Bosch genny's. And LUCAS switches! /bcforum/images/%%GRAEMLIN_URL%%/laugh.gif

 

[Nunyas]

hmmmm... sounds almost like a recipe for disaster...


oh wait, I'm running a Bosche Alt with Lucas switches and wiring in my B...

 

[tony barnhill]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]oh wait, I'm running a Bosche Alt with Lucas switches and wiring in my B... [/QUOTE]

Don't you guys know the Brits & Germans still don't get along!!

 

[DrEntropy]

Rob's got an Italian MGB!!! Who'd a thunk it.

 

[Nunyas]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]oh wait, I'm running a Bosche Alt with Lucas switches and wiring in my B...

Don't you guys know the Brits & Germans still don't get along!!
[/QUOTE]

But they work so well together! I mean, look at what the Brits did with the old German Bombed out areas!

 

[RonMacPherson]

Marelli or Bosch? Fun aren't they?