Alternator Problem

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Model T Ford Forum: Forum 2016: Alternator Problem
Top of pagePrevious messageNext messageBottom of page Link to this message  By Donald Conklin on Wednesday, February 24, 2016 - 08:00 pm:

I'm vacationing in Florida with my wife and brought my T touring along for company.
Two days ago on our way back from a StatePark, that was about 30 miles away, I noticed the ammeter was showing a steady 18 amps.
The battery is nearly new, restarting the engine didn't change any thing, the headlight draw was normal with the engine off. Lost some sleep thinking the cause and all the things that could be damaged by the apparent excessive voltage (battery, electronic ignition, electronic turn signals, etc.) I was ready to install an old but functioning generator I have with me.
I always disconnect the battery when when I park the car at night. I reconnected (switch) the battery in the morning, guess what, every thing functioned normally and continues to function normally.
Are the electronics in an alternator such that they can be effected by rebooting?
I hope it hangs in there thru the tour we will be attending at Lake Mary in early March.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Strange - Hillsboro, MO on Wednesday, February 24, 2016 - 08:40 pm:

Recheck the connections to the alternator and battery (including the ground) and make sure everything is clean and tight.

How old is the alternator? If the field brushes are worn and making intermittent contact, it can drive the voltage regulator nuts and you can see some big swings in charging voltage.

If it is working ok now, I would keep an eye on the ammeter, and if it starts acting up again, and if the brushes are easy to reach, you could try pulling each brush and stretching the spring that presses the brush down. That might hold you for the rest of the trip, but when you get home, if the brushes are worn, you should install new brushes.

Sounds like you have a good backup plan (old but good generator) if the alternator continues to act up. Good luck! :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Wednesday, February 24, 2016 - 11:59 pm:

What kind/type of alternator? If the voltage sense wire is loose or corroded, that will make the alternator think the battery is low and put the "juice" to it. The sense wire is usually a short jumper wire from the B+ terminal to #2 terminal on S-10 type alternators.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kevin Whelihan Danbury, WI on Thursday, February 25, 2016 - 07:07 am:

I'll second Mark's recommendation: check the ground. About the same thing happened to me last year when my generator spiked to the maximum setting with the lights off and just a small regular load on it when driving down the road. Did the same thing; shut it off and restarted. Things back to normal, then driving I hit a bump and it spiked again. After chasing the problem down, I found a loose and slightly corroded ground wire. Cleaned and tightened things up. No more problems since.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Thursday, February 25, 2016 - 09:31 am:

What kind of battery disconnect switch are you using? Most are made in China junk and are notoriously bad. Since operating the switch was the only thing you did between your two episodes, I'd bet money it's a faulty switch. As others suggest, anything that's open in the circuit will cause what you saw. I think your open circuit was in the cutout switch.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Thursday, February 25, 2016 - 10:35 am:

I agree with Jerry - those disconnect switches often cause big trouble and are best avoided. I've heard guys say "I installed a disconnect switch because I had a battery drain that was causing the battery to go dead over night".

This type of thinking is mistaken, you should be finding out why you have a problem, not installing something to mask the problem.

Alternators are impossible to judge without a volt meter. An ammeter is of little use when looking at alternator output. You need to check voltage at the battery with the engine running at the highest speed where alternator output does not increase. A good alternator / regulator will produce 13.7 - 14.2 volts at the battery. Amperage is not important, and can be misleading if your voltage is incorrect.


Top of pagePrevious messageNext messageBottom of page Link to this message  By G.R.Cheshire on Thursday, February 25, 2016 - 11:15 am:

Royce: I agree but I will add a caveat I installed a heavy duty "MARINE" disconnect for peace of mind.Old Cloth and tar insulated wires scare me I had an old Studebaker that had no signs of a short circuit when I parked it but some time that night a wire found some metal to lay against and completely destroyed my wiring harness. If you want to use a battery disconnect get the best money can buy if not at least disconnect your battery cable when you put her up for the night.... I consider it cheap insurance!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Donald Conklin on Thursday, February 25, 2016 - 10:36 pm:

Ken, I don't know what model of Delco alternator it is but I don't believe it's a S-10. There is no visible jumper.
Currently every thing is working OK so I don't think a volt meter will show me anything,but if the problem reoccurs I will be using one. The lights showed a normal draw with the ignition switch off so I don't think it's my "master switch" which is located down stream of the starter switch.
In my mind I think the alternator is the problem, but I don't know enough about the electronics involved. Wouldn't worn brushes cause erratic charging, this was steady at 18 amps. for 30 miles of open road driving.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Paul Mikeska, Denver CO on Thursday, February 25, 2016 - 10:46 pm:

A bad ground can make an alternator do goofy things. I had a similar problem and with the help of a good local auto electric company learned to run a ground wire from the battery directly to the motor and solved the problem. YMMV.


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