Older B7100d not charging

[Keith Smith]

I have an older B7100, probably a mid 70's model that will not charge the battery. I read that the dynamo should put out 40 volts AC. My dynamo puts out 26 volts AC. The regulator shows 12.5 volts DC from the red wire to the ground on the battery. I've heard that the dynamo can get dirty. Is it best to try and clean that first? It looks like a pain to get to. Remove front cover, radiator, fan, and then?

Any thoughts are appreciated.

Thanx,

Keith

 

[gcat]

I didn't a while back... The center middle nut is the difficult one... Read these..


www.orangetractortalks.com/forums/showthread.php?t=6816

www.orangetractortalks.com/forums/showthread.php?t=3934&highlight=dynamo

 

[Keith Smith]

If the dynamo is putting out 26 volts AC, is that sufficient? I hate to pull that if i don't have to. Do I need to set the polarity on the system? I've read a lot of information, but so much is inconsistent. I even read that you have to turn on the headlights to get the battery will charge. Seems odd, but I'll check that too.

 

[Apogee]

26 volts at which engine speed, idle or 2000 RPM?

Also, is that 26 volts measured at the leads with the dynamo disconnected or still hooked up?

 

[Keith Smith]

26 volts was measured at the leads disconnected from the rectifier at about half throttle. It drops to 20 volts at idle. I also measured at the leads up at the rectifier (with them disconnect from the rectifier) to ensure there was not a loss in the line. With everything hooked back together and running I only get an output of about 7 volts DC coming from the red wire on the rectifier, no matter if it is at idle or half throttle (about half the voltage that I would expect). I tried playing with setting the polarity, but didn't see any difference, no matter what wire I jumped. I'm starting to lean towards a rectifier. Keep the ideas and comments coming. I appreciate all the help I can get.

 

[Apogee]

Hi Keith,

Per the service manual, spec is 43.0v or more @ 4250 rpm across brown and white with them disconnected.

Spec is 30.8v or more @4250 rpm across brown and yellow. Hence, your 26v is not far off considering you were running at half throttle.

They way to test if it's charging is to disconnect one of the battery leads after you start it, put your meter in amp mode, and measure the current between the battery and the cable that you disconnected. Spec is 2.5 - 3.5A @ 4250 rpm with lighting on and battery fully charged.

I assume the 4250 spec is the actual dynamo rpm which likely translates to the engine revving at full governed speed.

I agree that it sounds like a bad regulator. Make sure to check that the regulator is securely mounted and the bolts aren't rusty. It takes a good ground for it to work properly and I've seen one where the mounting bracket had broken over time and the regulator was just hanging there. It didn't start working properly until I fixed the bracket and a good ground was re-established.

One other tip is to check eBay for a new regulator. They seem to be less expensive than the dealer if the correct one is offered.

Hope this helps!

Steve