TheSamba.com :: View topic - How do I know if my bus is charging my battery?

Tue Nov 10, 2009 3:27 pm

Desertbusman wrote: So you guys are only talking about Bays '72 and later, right?

I was, and by the OP's sig line, I think he was, too.

Tue Nov 10, 2009 3:33 pm

Desertbusman wrote: So you guys are only talking about Bays '72 and later, right?

Absolutely, and I thought I had mentioned that in one of my posts but it looks like I didn't. '72 and later for the functional battery light to charge the battery.

Tue Nov 10, 2009 3:36 pm

dwill49965 wrote: Desertbusman wrote: So you guys are only talking about Bays '72 and later, right?

I was, and by the OP's sig line, I think he was, too.

Right, I picked up on that also, plus knew the answer. Just thought it would be good to be clarified. Who knows, maybe some T-1 people didn't realize it didn't apply to them :wink: .

Tue Nov 10, 2009 3:56 pm

as to the low battery. Average life of a battery in the USA is about 38 months. If the battery is that age or older it may be bad and pulling the voltage down. The voltage will rise the closer it gets to fully charged.

Also - look to other causes - does your radio stay on when the key is off? If so are you leaving it on? I left the slider open the other night for awhile in the garage and looked up, the back passenger light was on. Is something like that going on? Do you have a stereo amp where it might be on although the radio is off etc.

Wed Nov 11, 2009 12:11 am

Quote: If the idiot light in the dash doesn't light up when you turn the key on, you have no charging. Period. No more what ifs...if you don't have the light on, you don't charge the battery. It can't be any more clear.

I am amazed. :? The previous owner of my bus must have messed with something because after revving the engine with the light disconnected I get 14.5volts.

Wed Nov 11, 2009 8:09 am

Nica wrote: Quote: If the idiot light in the dash doesn't light up when you turn the key on, you have no charging. Period. No more what ifs...if you don't have the light on, you don't charge the battery. It can't be any more clear.

I am amazed. :? The previous owner of my bus must have messed with something because after revving the engine with the light disconnected I get 14.5volts.

Well, you're partly correct and everybody else is partly correct also

You DO need the light to provide the initial field excitation current to get the alternator going. However the alternator will probably work without it anyway, once you rev the engine up, because of residual magnetism in the wires generates enough to juice for the alternator to start working. This works best with old alternators that have become slightly magnetized.

If the bulb burns out/falls when you are driving the alternator will not quit. Once it is working, it provides it's own field current. It just uses the current from the bulb for the initial start-up.

Wed Nov 11, 2009 8:38 am

WhirledTraveller wrote: However the alternator will probably work without it anyway, once you rev the engine up, because of residual magnetism in the wires generates enough to juice for the alternator to start working.

That describes my earlier situation exactly. When I started the vehicle, no bat light on, both voltmeters showed 12 volts, bus idling normal. When I stepped on the gas to move, bat light came on, both voltmeters went to 14 volts.

Wed Nov 11, 2009 9:03 am

dwill49965 wrote: WhirledTraveller wrote: However the alternator will probably work without it anyway, once you rev the engine up, because of residual magnetism in the wires generates enough to juice for the alternator to start working.

That describes my earlier situation exactly. When I started the vehicle, no bat light on, both voltmeters showed 12 volts, bus idling normal. When I stepped on the gas to move, bat light came on, both voltmeters went to 14 volts.

That makes sense. The Alternator light works by opposition of two positives. When the switch is on, engine off, current flows through fuse 12 through the bulb into the voltage regulator (light is on)

When the switch is on, engine on, the voltage regulator sends 12 volts back through the blue wire and no current flows through the bulb since it has positive voltage on both sides.

If you remove fuse 12, then there is no positive voltage to oppose the VR so the effect is reversed. You would expect that there would be no current flow, but looking at the circuit diagram I think there is a path to ground through the voltage stabilizer and fuel gauge.

Wed Nov 11, 2009 9:45 am

To the OP-

For what it's worth, when I had sluggish starting problems, I found that replacing the little ground strap on the transmission and the battery cables helped out a lot with that. Might wanna give that a shot; all those things are cheap.

Wed Nov 11, 2009 9:58 am

busdaddy wrote: 13.2v is pretty weak, your alternator may be telling you it's on the way out. Clean all the connections between the alternator and starter and alternator and regulator, pay close attention to where the wires enter the crimped on terminals and make sure the plug terminals are staying in the plug and making contact at the regulator terminals....

I'm looking for new or refurbished alternators. Are they the 55amp or 70 for the '77 Campmobile? Bentley only gives the VW part [021 903 023 A]

Wed Nov 11, 2009 10:00 am

It could have had either. Look at the alternator...if it has a fan on the pulley it's the 70 amp...if not, it's the 55.