Ammeter has a dancing needle

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Model T Ford Forum: Forum 2017: Ammeter has a dancing needle
Top of pagePrevious messageNext messageBottom of page Link to this message  By George Davis-Williams - Lake City, MI on Tuesday, August 08, 2017 - 11:04 pm:

I'm hoping that I can get some troubleshooting guidance on my charging system. I didn't see any suggestions for correction in the MTFCA Electrical system book. Before trouble shooting this myself, I thought I would seek your input....hoping it has an obvious or highly likely cause.

So here's the issue: The ammeter needle dances back and forth rapidly when going about 30mph. It goes from -10 amp to +10amp. When I slow down, it will settle to one point (2 amp discharge with lights, just over 0 when lights are off). So I just go slow.

I have not moved the third brush in about a month (the brush holder was broke, so after repair I readjusted to 10 amp charge at fast idle). Anyway, the needle didn't dance around until two days ago. I probably did 10-15 drives at the current setting without issue since the adjustment.

My thought is that I better re-adjust the third brush to see if that helps. Maybe it is pushed to far back and overcharging at higher RPM? But again, it didn't have this issue at higher RPMs for the first few weeks after I adjusted it last. My next thought is that I just have a poor connection somewhere...or a short. It has a voltage regulator, not a cut out...could it be an issue with the regulator?

Any input would be appreciated. Thanks!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Wednesday, August 09, 2017 - 11:34 am:

George,

You've got some intermittent open circuit or short somewhere. Or, maybe poor commutation. You also say you have a regulator. Is that really true, or do you have a traditional cut-out?? If you have a cut-out, it can also be suspect. Whatever the cause, don't run it like that or you'll likely ruin your generator.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Wednesday, August 09, 2017 - 11:35 am:

For starters, recheck your brushes to be sure they're in good contact with the commutator, with good spring pressure behind them.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Davis-Williams - Lake City, MI on Wednesday, August 09, 2017 - 12:40 pm:

Thanks Jerry. It for sure has a voltage regulator, I replaced the cut out a few months ago. I will check the brushes and spring/commutator tonight.

A little off topic: The MTFCA Electrical Book mentioned putting a generator ground wire on that is hooked to a switch so the generator can easily be grounded if needed. I'm not sure how I feel about that as a permanent addition, but I may temporarily add it as I am working on this issue... It would be a nice feature to have just in case I think I fixed the problem, only to have it return while on a drive.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Pete Humphrey, West Bend, WI on Wednesday, August 09, 2017 - 01:57 pm:

George,
Highly recommend starting form the beginning, otherwise you risk the gen as Jerry says.

Disconnect the battery and remove the regulator. Now solve the charging issues without the reg in the circuit. The Electrical Book has many easy tests as you know. Get the gen to be right. Then follow John Regan's advice on setting up the regulator, whether you bought it form him or not: http://www.funprojects.com/pdf/5055R6-052111.pdf His instructions are complete and correct. John would say that the voltage regulator is a great addition to a working electrical system, not the solution to a marginal one.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Wednesday, August 09, 2017 - 04:28 pm:

If you disconnect the generator or remove the regulator, unless you place a cutout you must ground the output of the generator or risk burning out the generator. The generator should always be connected to the battery through a cutout or regulator. Otherwise it will charge until it burns out without anything to charge.

Does this happen with the lights off and the engine running at a fast idle with the car parked? Or does it only happen when driving? Reason I ask is to eliminate bouncing of the car as a cause of the problem. If it is OK with the lights off, but happens when they are on, you might have an intermittent ground or open in the light circuit

However since you have had some problems in the past with the brush holder, first suspicion would be in that location.

Good luck
Norm


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