Last spring my wife and I went out to dinner with Bessie. When we finished she wouldn’t crank over, dead battery. I got some help and push started her but we just made it home, stumbling a bucking the last mile. The battery gauge was in the middle and I had no indication that it wasn’t charging. In fact, the gauge seems to always sit in the middle, or close to it. As I rev the engine it may creep up a bit, and a bit more when the headlights are on, I’m told that’s backwards but I can’t wrap my head around that. If the system is drawing more current to run the lights, the gauge should indicate that it’s drawing more.

I measured the battery at idle and revving, about 5.8 at idle and 7.6 revving, maybe 1500(?).

I replaced the brushes in the generator, and cleaned up the armature with emery cloth. I also put the battery on charge overnight and it never reached full charge, so I’ll be picking up a new battery before I’m back on the road. I haven’t tested the generator since the repair, but I will once I have antifreeze back in the radiator and the new battery.

Every vehicle I’ve ever owned gave clear indication if it wasn’t charging, or the battery was in bad condition. I didn’t get any in this case and I’m concerned that if the generator repair wasn’t successful that I’ll get stuck somewhere,

My question is…what is the best way to watch the electrical system while driving? Does it make sense to add a battery voltage gauge? Are there their methods to watch the charging system that are more reliable than the current loop gauge?

What’s the what what?

thx.

 

With the truck Off, turn on the headlights. Does the ammeter move about 10 amps towards Discharge?

 

Hopefully you fixed it. New brushes and cleaning the armature makes a big difference.

JB

 

An easy way to monitor voltage is with a digital voltage indicator that plugs into cigar lighter

 

That still confuses me. The meter is a current loop, not a charge indicator, so turning on the lights should INCREASE the current, not decrease.

 

I don’t have a cigar lighter, but I can tap into the circuit easily. I’m thinking right at the breakers.

 

With the engine off, headlights On, current flows out of the battery. Flows out of the battery shows as a negative .

 

ok. Looking at the schematic it’s getting clear. Current going from the generator to the battery shows as + but current going from the battery to other loads, like lights, show as a negative.

I think I have the meter wired backwards.

 

Which way does the ammeter move with the headlights on? Should move to DISCHARGE (left). Correct, although strictly speaking the ammeter shows the net flow.

 

Understood. I can’t test now, but I believe it’s backwards.

 

I’m getting a better handle in this. It’s hard to believe I have a degree in electronics. Of course it’s kinda old, they carved the diploma in stone because the printing press hadn’t been invented yet.

Yes, a current loop meter will show net current flow, in this case the meter resting position is in the center so it will show in either direction.

 

Well these are cool. I need to get one. I assume they will work for 6 volts without any issues.

 

I wouldn’t be too sure of that. All the voltmeters I’ve looked at start at 8v.

 

Hey Bob,
If you meaured across the battery about 7.6 volts while reving around 1500ish RPM, it sounds like its charging.
Was it running good driving to the restaurant?
How long were in there?
You mentioned the gauge crept up with the lights on? This was while it was running right? If I read that correctly it so that shows that the gauge is indicating that the voltage regulator is sensing an added current load, with a lower voltage at the battery and its adding field current at the Generator to make up for the lower voltage.
I would try Ross's test. Just hook up a charged battery , don't start the truck, turn on your headlights, and watch the gauge. It should swing over to the "D" side.
I could be wrong but I am thinking you just have a battery that is no longer holding a charge.

 

driving to the restaurant with no headlights it ran great. We were there for maybe 1.5 hours or so, and I tried to crank.

You’re not wrong, the battery is kaput. I’m also concerned about the regulator, I’m not convinced these repos are any good. I bought another so if I can’t get this one adjusted correctly I’ll replace it.

My concern is that the generator couldn’t keep the truck running with headlights on, so I may be able to charge with no load, but can’t supply enough current, and the voltage drops. At one point I measured just over 5v at the coil and the engine stumbled badly. I thought we going to have to walk the last mile but I turned off the lights and we JUST made it, stalled in the driveway when I dumped the clutch.

Im fairly convinced I wired the gauge backwards when I rewired, once I get a battery in I’ll do the test.

Thx for the help.