TheSamba.com :: View topic - Gen Light On, Brake Light On, Alternator Not Charging Bat

Thu Oct 29, 2009 4:59 pm

I've search this and am not sure I understand all the possible causes. Bus is a '73. As mentioned above, the generator light on the dash is on bright and constant. The brake warning light is also bright and constant. And the alternator is not supplying current to the system. Lights dim down, battery dies, then finally the engine shuts off. I recharge the battery and it starts right up.

I've been reassembling the Bus after paint. This was not an issue before I disassembled, which included the dash. I'm pretty sure everything is back in place as far as the dash wires are concerned. All systems now work. Nothing was taken apart in the engine bay.

The brakes have been bled and work fine so I don't think that is contributing to the brake light issue, and previous posts suggest both the gen light and the brake lite come on when there is an electrical problem. The positive cable on the battery was loose. I pulled the terminals, cleaned, tightened, no change.

The alternator is about a year old.

Voltage at the battery is 12.5. Voltage with the engine rev'd, still 12.5.

Baffled? Suggestions?

Thu Oct 29, 2009 5:23 pm

Check your fuses. number 12 iirc.

Thu Oct 29, 2009 6:10 pm

Wherever you got that fallacy about the brake and charge lights indicating an electrical problem get it out of your head now, I can't imagine a circumstance that would bring that on.

When you remove the plug from the voltage regulator and ground the blue wire in it when the key is on does the alt light come on?

Thu Oct 29, 2009 6:34 pm

This might help you...

http://www.ratwell.com/technical/ChargingSystem.html

Thu Oct 29, 2009 6:43 pm

Fuses are all intact, including # 12.

If I pull the regulator connector and ground the blue wire, the "G" alternator light still comes on with the key turned on.

Thu Oct 29, 2009 6:52 pm

Please follow the blue wire from the Voltage Regulator and make sure it's hooked up for the front signal lamp. There is a connector - clean it and check that the wire isn't damaged where it goes through the firewall. Clean and check connections at voltage regulator.

Check belt tension on alternator pulley.

If your alternator is really only a year old is SHOULDN'T be the problem. These should do it.

Check Ratwell site for test procedures for alternator and regulator if these don't clear it up.

Frank

Thu Oct 29, 2009 7:48 pm

I ran Ratwell's voltage check at the regulator. My numbers are nowhere near his. Biggest issue is I'm at 3 volts at idle on D+. The only number near the ballpark is D-, they all match at zero.

Seems to be pointing to the alternator.

But I'm not ruling out a connection issue. I still need to pull all connectors in the circuit and clean. Some things under the dash definitely got wet.

BusDaddy: I knew I hadn't dreamed the relationship between the brake warning lamp and the "G" lamp. They are on the same circuit. Blue wire feeds from the regulator to both. I confirmed this in the circuit diagram as well. I'm not sure if my electrical problem is actually related to my brake light problem, but I'll find out once the first one is fixed. If not, then I'll move on to the brakes.

Thu Oct 29, 2009 8:01 pm

BampaBus wrote: I ran Ratwell's voltage check at the regulator. My numbers are nowhere near his. Biggest issue is I'm at 3 volts at idle on D+. The only number near the ballpark is D-, they all match at zero.

Seems to be pointing to the alternator.

Are you testing the D+ like in this pic?

and only getting 3V? with the engine running?

Thu Oct 29, 2009 8:09 pm

Yes, that is correct.

My numbers with key off were a little higher than his, excluding brown, of course.

Thu Oct 29, 2009 8:26 pm

1st vote for bad alternator diode....

Can I ask where your Alt. came from?

Fri Oct 30, 2009 12:13 am

I just got done replacing the alternator in my 71 (had the alternator conversion). What a pain in the butt. I have been having issues with the old one kind of like your but my break warning light is inop. For about the last month the turn signals caused a slight miss in the ignition and after about an hour of driving with the lights on the miss would return until she just died at a traffic light. I replaced the battery but it wasn't charging either so I realized that the alternator was toast too.

Best of luck figuring yours out. I don't really have any advice for you other than if you change the alternator be patient.

Fri Oct 30, 2009 3:34 am

I'll pull the alternator and have it tested.

I'm not sure of the source. I was having a lot of work done about a year ago and the mechanic replaced it. I can find out, if it is really important.

Fri Nov 06, 2009 3:42 pm

Issue resolved. It was the alternator. Still under warranty (2 years, Bosche). I installed it this morning and it's back to normal. I tested it and it's appx. 14 volts at the regulator.

Both the alternator light and the brake light went out. I still don't understand why, but the alternator was the source of both lights.

Fri Nov 06, 2009 4:03 pm

Good news!, the brake light comes on with the alt light to prove it works every time you drive the bus, when it comes on while driving and the alt light doesn't you need to worry.