The Stovebolt Site Forums The Shop Area The Electrical Bay Charging delco gen bendix regulator

First off let me say I am not great with electrical. With that said, I have a 1954 3100 with delco gen and bendix regulator the system has been polerized, gen is putting out 35 volts at fast idle, I have 14 to 16 volts output at the bat terminal on regulator and I have the same at the starter for that matter down to the battery.

The problem is when I check voltage at pos/neg on the batery I am only getting voltage from the battery about 12.8 however when I ground the volt meter to the body or frame I get 14 to 15 or so volts. So I changed the ground cable, same thing. I am positive all the connections are clean still no charge to bat although the bat dose take and hold a charge from my battery charger??

Any ideas because i'm stumped everything I see says it should be charging.
Oh! The volt meter on the truck dose not read a charge either.

Presumably, you have a 12v generator and a 12v voltage regulator and a 12v battery (1954 was originally 6v)?

Is the trucks gauge a voltmeter or and amp meter. A volt meter gauge would show 14-18, a amp meter gauge can show near zero or dead center. It will fluctuate when loads are applied and remove from the battery. You should see w jump for instance when headlights turn on. If this occurring then the system should be OK only when it stay 0 or stays to the left or right something is wrong in the battery + pos current line to/from the truck.
With the fact your only seeing 12.8 on battery with truck running leads me to think your regulator to the battery + has a problem in the line. But the confusing factor is the 14-15 volts on battery terminal to frame ground looks more to the ground lead. That would indicate issue in the battery terminal connection itself.
But one other factor to consider the battery does crank over the engine so the ground and battery to starter are good. So it has to be on the smaller battery to amp meter or regulator.

If your generator is putting out 35 volts then it is not connected to the battery through the regulator. I don't know about the Bendix regulator but you should have a Delco on there.

35 volts with the field grounded bybasing the regulator

Im not sure if it's a volt meter or amp it just reads c or d with center line. When I use anything in the truck it goes to the discharge side. Like I said I am absolutely stumped with my hand held volt meter reading 14 at the positive post grounded at the frame and 12.8 at the battery post neg. The darn thing starts and runs the light work etc??

If you gauge has a C and a D it's an ammeter. C for charge, D for Discharge. Don't forget there is resistance in the battery cables, both positive and negative sides. As current flows through that resistance it will create voltage drops. The higher the current flow the more voltage drop. The higher the resistance the more voltage drop. Sounds like everything is working fine. Formula is V=IR, Voltage Drop = Current times Resistance. It doesn't take much current across a low resistance to start shaving off volts. For example, charging the battery back at say 2 amps, across a .5 ohm resistance will drop you 1 volt. V=(2)(.5) It's not hard to add up to .5 Ohms by the time you factor in the resistance of the battery cables, the battery lead from the regulator, each wire connection, the internal resistance of the regulator, the internal resistance of the battery...... The reason you are seeing a different voltage reading frame to battery positive post vs reading across the post is that you are only reading the voltage across the batteries internal resistance when reading post to post. Reading frame to post adds in the resistance of the wires, connections, and the internal resistance of the regulator as well. Each component (regulator, cables, connection, battery) adds resistance to the total circuit that the current must flow through. And each component will drop a small amount of voltage across it's resistance.

Got a new pos cable and new battery load test states battery is bad. Will see if charge holds up.

Just to throw in a few numbers here, if your starter used 100 amps when starting, the total resistance of your starting circuit including the wire from battery to ground would be 6/100 = .06 ohms. If that wire were .5 ohms, your starter could not draw more than 6/.5 = 12 amps. No starter will turn your engine over with only 12 amps.

truckernix you are correct. I don't know what the total loop resistance is, just giving an example of how each link in the chain, so to speak, creates a voltage drop as current flows through it. When starting we have the resistance of the battery cables, connections, and the battery itself. (technically the starter too). When charging we have the battery cables, connections, the battery itself, plus the resistance of the charging circuit added to the mix. The path of the current flow for starting vs charging are different. If there were a high resistance connection on say the battery lead from the regulator to the battery or within the regulator itself through worn relay contacts but everything else was fine (battery, battery cables, etc.) it wouldn't factor in on the resistance affecting current flow to the starter from the battery. It would only show up during the charging phase. But it sounds like he's found his battery to be defective under load test. So my post is nothing but academics!

A bad battery will read just like you found. A charger will try to charge it and when you take the charger off, the battery will read 12 Volts and you think it is OK. Put a headlight on the battery as a load. I use an old connector and some clips. Then read the battery with the light on. Less than 12 Volts and the battery is toast. Old hot rod set up for Bright/ Dim was to run both as bright, and dim alone. Saved money on the switch. More money for go fast stuff. Light bulbs were a little short lived but who cared. However, when the generator was not generating those lights got dim fast.

Ends up my charging system was not working so I bought a new regulator. When replacing the regulator I noticed a very old style type fuse which was partially burnt. I replaced the regulator anyway and the system was charging great. I drove the truck a couple of hundred miles no problems charging great.
Then, I started the truck drove a couple hundred yards the generator was making a metalic grinding noise and could smell faint wire burning smell. I popped the hood and noted the generator smoking a bit and the wires to the generator burning hot. I immediatly disconected the battery. I let everything cool including a very hot new regulator. So I disconected the gen wires and reconnected the battery no prob truck starts runs and everything works except the charging.
Any saving the old system? Is best the convert to alternator system? If so whats the best way to go about it?

So I ordered every thing for the switch, BBB Rebuilt 7292-9 regulator Amazon 65 bucks, bracket and harness 75 bucks classic parts. Could have saved 30 bucks on the harness but just didn't feel like making it myself.

The alternator is installed and works perfectly. The harness was worth the purchase the bracket was over priced and required slight modification as well a new slightly shorter V belt. Oh! Correction on the price, it was just over 90 bucks for the harness and bracket. The conversion was totally worth doing but I do miss the original look of the generator.