Amp gauge swinging from + to -

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Model T Ford Forum: Forum 2018: Amp gauge swinging from + to -
Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Duthler on Wednesday, August 01, 2018 - 03:03 pm:

My 1919 T just started having the amp gage swing from -10 to +10, and the rate varies with engine speed. Yesterday it was fine. Any ideas what is happening? The engine seems to run fine, but I'm not sure the battery is charging.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Wednesday, August 01, 2018 - 03:29 pm:

I'd would check first for loose terminal fittings at the back of the ammeter.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Wednesday, August 01, 2018 - 04:21 pm:

Mine did that on the Redwood Trees to Pacific Seas the first day. Next day, zero all the time but discharge when the lights were on. So I used the crank the rest of the tour. When I got home, I changed the generator to a rebuilt one and it works fine. I think the problem is in the brush plate of the generator.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Wednesday, August 01, 2018 - 05:06 pm:

Can't state what exactly but the gen is my guess too


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Wednesday, August 01, 2018 - 06:30 pm:

While it certainly CAN be the generator I would check the 5 wires in the charge path for a possible bad connection or looseness.

1) Yellow/wBlack tracer wire from generator mounted cutout (or Voltage Regulator) screw terminal to terminal #1 on the leftmost connection at the barrier strip. This wire is enclosed in a harness with other timer wires typically.

2) Yellow/wBlack tracer wire from terminal #1 on the barrier strip to the BAT connection on the ignition switch. Again this wire is in a harness to the ignition and lighting switch.

3) Yellow/wBlack tracer wire from the BAT terminal on the ignition switch to one side of the ammeter. - This is a short jumper wire and not in a harness.

4) Solid Yellow wire from the other side of the ammeter to terminal #3 on the barrier strip. #3 is third connection from the left at the barrier strip. This wire passes via a harness through the firewall.

5) Solid Yellow wire from terminal #3 at the barrier strip to the BATTERY SIDE connection on the starter floor foot switch. This is the connection on the switch that is always hot and goes to the + (positive) side of the battery via a heavy battery cable. This wire also passes via a harness through the firewall.

ALL 5 wires should be #12 AWG heavy stranded wire and the connectors on each end should be tight, clean and hopefully soldered. Compare the outside diameter of the Yellow/wBlack tracer wire to the outside diameter of the Solid Yellow wire. Many reproduction harness' were made with #14 wire for the Yellow/wBlack tracer wires and will be noticeably smaller in outer insulation diameter when compared to the Solid Yellow colored wiring. Original harness was ALWAYS #12 AWG for ALL 5 WIRES and something you should fix eventually to lessen the burden on your generator due to excessive voltage loss in the wiring path from generator to battery.

Use of #14 is in error but will NOT cause the problem of having a bouncy ammeter unless there is a loose connection to go with it. The use of #14 for 3 of the wires will just result in slightly dimmer lights and a longer time taken to recharge the battery after the engine starts. If the wiring is even smaller than #14 AWG then you MUST replace it before you proceed. DO NOT use Solid Copper conductor type wire for automotive wiring harness connections due to vibration which can break solid conductor wires eventually.

Hope this helps.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Duthler on Thursday, August 02, 2018 - 01:22 pm:

I'll check this out - may be a little bit before I can get to it; I'll post what I find. Thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Neil Kaminar on Friday, August 03, 2018 - 08:27 pm:

Brushes could be worn and not making full contact or the brush springs could be bad or the brushes could be stuck. Try light oil first. Work the brushes up and down. After the oil doesn't cure the problem, push down on the brushes to see if the brushes are worn. If the generator output improves when you are pushing down the brushes are worn out.

Neil


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