My belt-driven alternator has always shown a 2-amp discharge when the engine is idling. _I can center the needle or send it into the positive side of the ammeter's arc by increasing RPM. _If I turn on the headlights, the discharge becomes greater than can be overcome with moderate revs, so something is definitely wrong. _The car has behaved like this since the day I bought it.
The mechanic who does my annual state inspections said that what I need is a smaller pulley to increase the RPM of the alternator in proportion to that of the engine.
But my understanding is that once a correctly operating alternator reaches its charging RPM, it will continue to charge (or at least will not discharge) regardless of RPM, until the next time the engine is started. _Is this correct?
Has anyone else had and solved this problem?
Bob your mechanic is correct, a smaller pulley will give you enough rpm to start charging, i have the same setup on my model a pickup, i had the local alternator and starter repair guy put in an agricultural regulator that starts at an ultra low rpm something like 800 rpm. but i still have to rev it slightly after it warms up and then you can see it start to charge. once the field is exited it will continue to charge at any rpm.
I should have included these photos of how my alternator is wired up. _Maybe that's the problem?
My experience is they will always discharge at idle and i wouldn't worry about it. Slight rev and your charging, this is the way every car I have owned has operated. I fitted a gear driven Alternator to my T and it its perfect, slight rev above idle its charging, a bit more if the lights are on....that's good!
sounds ok to me!
A smaller pulley will go a long way towards fixing your problem.
I have a Becker 6V gear-driven alternator on my car and the alternator gear is puny compared to the camshaft gear that it meshes with.
Put a piece of duct tape over the ammeter so that you can't see it for a couple months.
If the battery stays charged then you have fixed the problem.
Funny, Royce !
Scott and Kevin,
A slight rev won't do it, especially if the headlights are on. _It takes quite a bit of rev (like when I'm cruising in high gear) to get the needle deep into the plus arc. _But I remember back when modern cars had ammeters, no matter the speed of the engine, there was always a slight positive needle deflection. _Any other indication meant something was wrong. _The needle shouldn't swing way to the left at idle and then way to the right during cruise — right?
I'd be fine with a smaller pulley if that were the correct answer, but something tells me there's something fishy in the circuitry.
Ignoring the ammeter causes the 12-volt, red-top Optima battery to slowly empty itself of charge. _I have to use a charger every few weeks to bring the battery back up to full and I know it's not healthy to deep-cycle a battery like that.
Remembering all the trouble with the starter and battry would it be better to just turn whatever it is back to a Model T?? Bud in Wheeler,Mi.
Mine is a working car—a daily driver, not a show car—and I traffic jam on Jericho Turnpike with tractor-trailers, buses and rap music-blasting Mustangs driven by hat-backwards kids who change lanes like pinballs. "Penelope" is equipped to handle that kind of traffic and being able to re-start instantly after a flame-out increases my margin of safety considerably.
You are one brave soul to tackle Long Island traffic it a T - electric start or not!
Kudos to you - Braveheart!
Bob I've owned hundreds of cars in my lifetime (mostly with generators) and I can't remember a single one that has ever been on positive on the amp meter when the car is idling....not one and definitely not if the lights are on as well, but only about a quarter of the way into the negative not all the way down.
In saying that I have fitted a gear driven alternator to my T and its perfect. Slight Negative at idle (which in my opinion it must be) but lifts into positive with slight revving. Driving with the lights on in top gear its positive unless the engine is chugging very low revs.
If it takes several winds to start the car it will then only read a maximum of half the positive side (+10) for a few minutes to charge back up then it will sit a mick hair above zero. The other day I started it several winds at the supermarket, then drove off and turned the lights on at the same time and it blew my original style (-20 0 +20) amp meter. I had ordered a $7.50 (-30 0 +30)amp meter when I got the Alt because this is a common issue with the higher output from an Alt, I have now fitted that and its all good. Pleased I put a 20 amp fuse at the Alt as this blew at the time.
I agree the really big negative to really big positive swing doesn't sound right, make sure you have a fuse in the system just in case.
Yeah, that's what I'm thinking, Kevin. _My ammeter is acting like a tachometer. _I need to figure out whether the thing has been installed correctly, whether it has an internal voltage regulator or needs an external voltage regulator installed.
From what little I know about automobile electric's, an alternator becomes efficient to produce needed voltage and amperage at rpms above 1,000. The max rpm of a stock Model T Ford engine is 1,200 to 1,500 rpm. At maximum engine rpm the alternator would start to produce noticeable electricity. To increase the alternators electrical output the pulley needs to be changes in size usually to a smaller diameter size. There are internet articles for helping with calculating the pulley size one can be found here:
I have never hAd a charging system on any of my Model Ts until two weeks ago when I bought Popeye. If I install an alternator it will have a volt meter.