Recently if I let SaraJane sit for more than a week the battery is completely dead. It is a 12 volt system with a Texas T alternator. I made sure no lights were on and the key was off same thing. Disconnected the battery and it maintained a full charge. I started checking all the connections and I found that I always have 12 volts at the wire to the alternator. Do I possibly have a problem with my ignition switch? Or should I keep looking for something else?
Simplest? Unplug the alt. and see if it goes dead over time. Since it's OK disconnected you obviously have a drain. Believe it's normal for 12 at the alt at all times but not a drain of course.
That alternator probably has a V.R. built in causing the problem.
When SJ is at rest, current drain thru the alt should easily be detected. Alt regulators are easy replaced. Jerry.
Bad diode...thats common
I have a sort of similar problem with my Texas T alternator. _The darned thing discharges at a rate of minus-2 amps whenever the engine is idling. _Bringing up the idle up a few hundred RPMs will swing the ammeter's needle to center, but alternators aren't supposed to work that way. _Well, that's how mine has been behaving since it came out of the box, six years ago.
I got in touch with the dealer who pointed out that the Texas T alternator is of the agricultural type—meaning it's optimized for operation at low RPMs, which makes it ideal for a Model T. _Okay, that meant there was probably something wrong with mine. _What to do, what to do? _Well, I could have dismounted my unit and sent it back to the dealer, but as it was out of warranty, that made no more sense than taking it to some local electric shop.
Now, taking the unit out of the car might not be the answer because it's possible there's something wrong with the way the alternator was installed and I could get it back with a clean bill of health and the same problem with which I started out—except my wallet would be a little lighter for the experience.
Taking the whole car to a national-chain Service Station just didn't work. _Modern-car mechanics don't particularly like trouble-shooting electrical glitches on cars this old and their well thought-out solution was, "Just keep the RPMS up." _Hubboy. _Another problem is that I can't just leave the car with a mechanic and expect him to be able to move it around as needed, because driving a Model T isn't the kind of thing you can learn from watching Sesame Street.
Oh, sooner or later, I suppose I'll find a cooperative automotive electric specialty shop that will welcome my business, but until then, I'll just keep hooking up the car to a charger about once a month to top off the battery.
For those running alternators - what device on your car needs the 750 watts that a typical alternator puts out? Seems like you are putting up with a lot of inconvenience to get something you don't need.
just my .02
I run a 6V alternator because the shop that did the restoration for the previous owner of the car installed it.
I do have a fresh Patterson rebuilt generator and a new Fun Projects regulator in the basement waiting to go onto the car if the alternator ever gives me trouble.
Modern alternators with built-in regulators do have a slight "draw" on the battery when not running; the draw is very slight, and should not run down a good battery for a few weeks. Most "everyday" cars don't sit for weeks without being driven, so this isn't an issue for them; but our cars can sit quite a while at times, so it does become an issue!
I initially thought it might be a diode and tried to get the rebuild kit for the alternator but none of the parts houses can help me unless I can find the original GM /Delco part # for the base alternator that Texas T parts used to make one for the T I have been wanting to convert this one back to a generator and 6 volts since I bought it so maybe I will
Put a switch in the wire going to the gen./alt. Turn it off when the engine is off. I had the same issue with the Texas T alt.
I put a relay in one of the other cars with a distributor. Key goes off. Wire to gen/alt goes off too.
I had this happen on one of my cars that came to me with a single wire alternator. Long story short I took it to a very good re-builder and they could find no problem with the unit. I re-installed it and the battery discharged right off of the bat. When I called the re-builder to complain I was lucky enough to get the owner of the shop on the line. Here is what I learned from him. A single wire alternator must have an absolutely flawless ground path to the battery. If it doesn't it will discharge your battery when the car is not running. Even just a couple of ohms resistance will make this happen. Run a ground wire directly from the battery to the motor, or better yet to the alternator and this problem will go away. I ran the ground wire and the problem went away. I could not believe this was really the problem and pulled the alternator off of the car and tested on my work bench with jumper wires and an assortment of resistors. I found that as little as 5 ohms resistance would make my alternator discharge while at rest. YMMV but I doubt it!
Recently had a T with this issue, in this case it was drawing a constant 2.87 amps at rest. The problem was one of the diodes, replacing the diode pack complete solved the issue. Depending on the make of alternator depends how easy access to the diode pack is.