alternator vs generator

[19_again]

Before I begin, I want to remind Jack and Doc that they said the only dumb question was the one you were afraid to ask. Ok?
My battery won't hold a charge, I've searched the archives and see references to alternator pulleys and more. My '66B has no alternator as far as i can tell. It has a generator which occupies one third of the fan belt's pulleys. Fan belt is tight enough, battery is new (2 weeks). As I was out for a drive today, the car started sputtering as if getting no fuel.
eventually came to a stop, hooked up the handy jump unit, fired right up, left the charger/jumper hooked up and headed home. As long as it was hooked up it ran fine, but one of the
clamps came loose and it stalled again. Could it be a nad generator? I know it sounds like a bad alternator, but I can't find one. DUH?

 

[PAUL161]

You can check your generators output with a volt meter. If it's putting out between 12 and 14 volts it should be ok. If that's the case, I would check the voltage regulator. It might need replacing. With all of this said, I'm assuming that your battery is in good shape and will hold a charge. PJ

 

[19_again]

Thanks Paul, Yeah battery is good. I have had a problem with my fuse block (new one coming tomorrow) in that the bottom fuse needs to be manipulated every now and then. My horn or gas gauge will stop working, I'll reposition the bottom fuse and it's ok. I figured the box may be damaged or cracked. I will check the output on the generator, with engine running I assume. Is there no alternator on this car, in your experience?

 

[PAUL161]

Not unless someone converted the car prier to your ownership. The early cars came with a generator. A generator works very well when it's in good condition. The brushes get dirty, and/or wear out and need replacing on occasion, but not to often. The main difference between a generator and an alternator is, an alternator will charge at a very low RPM, where a generator needs a little faster speed to charge, but, a generator will charge up a completely dead battery, if it is chargeable, where an alternator will not. An alternator needs some voltage to excite it into a charging mode. Nothing wrong with a generator, they'll take more abuse than an alternator, plus the generator is proper for your car. Even looks better in my opinion.

 

[Steve_S]

I would first suspect the control box. It also sounds like it might be time to check all your connectors. One at a time, pull each one, clean and reassemble with a small dab of dielectric grease. Also make sure the grounds are clean and tight. Generators have the advantage of being very durable, even being unaffected by reversed polarity.

 

[David_DuBois]

A generator is long and black, whereas an alternator is short and silver.

When checking the generator, disconnect the regulator from it so that the results you get are from the generator alone and not being modified by the regulator. Follow the following procedure:
Check the generator/dynamo by disconnecting the wires from its terminals, connecting the two terminals together and to a 20v voltmeter (preferably an analog meter rather than a digital). Start the engine - DON'T rev it!! - just slowly increase the revs watching the voltmeter. It should get to 20v by the time you get to 1000 rpm. DON'T exceed 20v (since the generator is getting unregluated feedback in this test it will incerase above 20 volts very quickly and if allowed to, will continue to increase until it destroys itself). Note: if you cannot get the generator to produce 20V in this test, even if you get 12V or 14V, but no more, the generator is bad. If that checks out reconnect the wires to the dynamo with the voltmeter on the D terminal (brown/yellow wire) and again start up and slowly increase the revs watching the voltmeter. The voltage should rise then stabilize at about 14.5v, it goes higher again don't let it go over 20v. If it stabilizes at 14.5v it is charging OK.

One more thing, if you have a generator, then loosen the fan belt. From your description, you have the belt way too tight. You should be able to push between a half to three quarters inch slack in the belt between the generator and water pump pullys (not on the longest leg of the belt) without undue pressure with your thumb. This is very important because an excessively tight belt will cause the rear bushing in the generator to wear rapidly and will soon cause the armature to start rubbing into the field coil pole pieces. A generator doesn't produce the back EMF that an alternator does when current is being drawn and thus doesn't produce a drag against the belt. I always ran our cars that had generators with the fan belts loose enough that I could rotate the fan with only one finger (without the engine running).

 

[DrEntropy]

/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif

I'll keep the generators in my old lumps as long as I can get brushes and bearings! Even considered one of the old Bosch genny's and regulator from earlier Alfas as a retrofit on the Spider. Too much fussin' tho.

 

[jlaird]

Generators can be checked for free at Autozone of course. but the methoid above works great.

Too tight a fan belt wears the bearings fast.

 

[19_again]

When I do this I'll need to have warmed the engine up in advance since choking it will produce revs in the 1800-2000 range. Even when idling I'm around 1200. Or is it more important to watch Volts than rpm's using the 20V as the MAXIMUM no matter what?
Thank you,
Mike

 

[PAUL161]

Mike, The voltage regulator should take care of any voltage overload coming from the generator. It senses the amount of charge in the battery and lowers or increases the amperage going into it as needed. Amperage is what needs to be controlled more than voltage, to a point. Newer cars with meters in the dash in relation to lights, usually indicate volts which I think gives a false thumbs up about the system. Example; My alternator went bad in one of my vehicles. The volt meter indicated it was putting out 14 volts and it like to of drove me crazy trying to figure out what was wrong. I pulled the alternator,( a 120 amp unit), had it tested and found out it was producing 14 volts but only 4 amps. No instrument in the vehicle indicated amperage. So voltage and amperage both need to be checked. PJ

 

[David_DuBois]

Generators and alternators are two different animals. The above test for generators is a time proven test (it is contained in both the original shop manual for the car and the Lucas manuals), and it must be done as discribed, with the regulator out of the circuit to give a meaningful result. It is not a comprehensve test, but a quick test, checking the overall health of the unit. A test for current supplied romthe generator requires the use of a carbon pile, variable load to handle the current flow that is normally not available to the home mechanic. I have tested dozens of generators with this method and all that would produce the 20 vols worked fine in the car. the one that would only reach a maximum of 12 volts needed repair. If a more comprehensive test is wanted after doing the above test, then by all means take the generator to a good auto electric shop and let them test it on their set up, but be aware that if the person doing the test doesn't know what he (or she) is doing, they can tell you that a bad generator is good (the generator that I found bad was given a good bll of health by a local shop - one that I no longer go to).

Doc - The bearing for the generators is a standard bearing that cn be purchased locally from a good auto supply house and the bushing can always be turned out by a decent machinist from some oilite material.
Cheers,

 

[DrEntropy]

Yup, I know, Dave. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif That was what I meant by: "as long as they're available". Bearing is a 6502 IIRC.