TheSamba.com :: View topic

Sun May 13, 2012 10:30 am

Put a donor 1600 SP in my buggy. It has an alternator (Motorola) that uses an external electronic regulator.

This alternator/regulator set up charges the battery and keeps it charged very well.

It doesn't boil over and it never prevents the battery to go un-charged.

However, when the alternator kicks in to charge, (I have a volt meter on my dash), it charges wide open every time the alternator turns on to charge. It pegs out at 18V.

One night I was driving and my sealed beam headlights turned into the brightness of camera flash bulbs just before they both blew out. I mean they got BRIGHT too! Since then, after replacing the headlights and getting caught with driving at night I have learned to push the clutch in and allow the engine to go to idle when the alternator kicks in, but even at idle you can easily see that the lights are getting extra juice, but this helps prevent them from blowing out again, but not a garrantee. So I try not to get caught driving at night time because of this problem.

What would most likely be the cause of this? The VR seems to be cycling properly when the need for battery charge arises. When the VR cuts the Alt on the Alt charges for about 20-30 seconds then the VR shuts off the charging.

I had even tried a new VR which made no difference.

Sun May 13, 2012 6:57 pm

The electronic regulators really don't cycle. They should just try to keep the alternator output at a fixed voltage. Something around 13.8V or 14.0V. The fact that you see it going on and off is a sign something is not right. Here is a schematic of what is going on:

http://www.nls.net/mp/volks/schem/mot_alt.gif
...and
http://www.nls.net/mp/volks/schem/altreg.gif

If you've swapped the regulator with a known good one, you may want to double check the wiring.

I'm not sure of the internals of the motorola regulator (even though I work for Motorola!) but it may just be that it goes "open loop" if there is no ground. Maybe somebody else can comment.

Oh, and it looks like there isn't a separate ground wire, but the regulator definitely needs to be grounded. I assume the case is ground and needs to be well grounded.

Regards,
Dave

Dave

Sun May 13, 2012 7:16 pm

Correction, It looks like the D- terminal is tied to ground inside the alternator. So the brown wire IS the ground wire. Not the case. I'd double check that wire.

Dave

Mon May 14, 2012 12:27 am

I am wired exactly like that of the colorful second schematic link.

I will re-check my regulator ground, alternator housing ground, Alternator D- terminal for ground, also going to pull the alt brush holder and look at it.

The cycling seems as if it were a normal thing, but just that when it goes on it pegs out my dash voltmeter which only goes to 18V for about 20-30 seconds and then the volt meter cuts back to normal battery voltage.

If I find the culprit I'll post what I find has caused it.

Thanks Dave.

Mon May 14, 2012 6:50 am

Really sounds like a regulator on it's way out....

Dale

Mon May 14, 2012 8:38 am

Dale M. wrote: Really sounds like a regulator on it's way out....

Dale

Yeah, I would ditch the alt/reg combo and just get a new alternator from Autozone or Checkers or something and wire it up.

Problem solved.

Mon May 14, 2012 5:23 pm

Ditto.

If you're seeing voltage spikes as high as 18VDC with the battery connected (a battery helps dampen sudden changes in DC voltage), then I'd hate to see what kind of voltage that thing is putting out at that moment. Wow!

Mon May 14, 2012 6:19 pm

Mine charges ok for a few weeks, then the battery gets weak. Alternator locked up 2 months ago and I had it rebuilt. It did this before the lock-up. And does it now... But not as frequently... It is a bit better. There is 0 voltage drain from the battery when its in in the garage. Headlights and turn signals are bright at night. The alternator makes a "singing" noise when you have the headlights on. It did the same before the re-build but was even LOUDER then.