For The 50D Alternator Experts

luvrbus · March 21, 2012, 09:29:32 AM

Ok on a 24V GM before I install a new high dollar regulator here is the problem the alternator charges at 32+ volts and will not cut back like it has no ground with ground connected you get a good reading but still charges at 32V, you disconnect the ground and I get a reading of 5v on the ground wire and the alternator still charges at 32v.

Help me out here guys I never ask for much is this a wiring problem or regulator the wiring is in bad,bad shape on this 4905

good luck

Ed Hackenbruch · March 21, 2012, 10:26:29 AM

Clifford, is there an adjusting screw on the old regulator? Mine can be adjusted up or down somewhat, but i don't know what kind of range it has.....8v difference seems like a lot. (disclaimer,....electrical stuff is my weakest suit.

)

Busted Knuckle · March 21, 2012, 11:03:21 AM

Clifford I wish I could help you, But GM's and electrical are my WEAKEST subjects.
<y only suggestions is/was the adjustment screw on the regulator an Ed stole it from me & beat me to posting it.

If there were ever anyone on this board I'd do anything for it would be you! (well and most all others. But as much as you have helped all of us, I certainly hope someone/anyone can assist you with this!)

BK

luvrbus · March 21, 2012, 11:48:38 AM

The adjusting screw does nothing Ed I tried that first this thing is driving me nuts

Utahclaimjumper · March 21, 2012, 12:09:08 PM

Cliff,, using a scrap piece of wire,, run a ground directly from the alternator ground to the regulator ground ( don't use the frame) If it clears up you have your answere,, if not then its the reg..>>>Dan (Also make sure the reg. frame is grounded well)

Sean · March 21, 2012, 12:26:25 PM

Clifford, does the alternator have a single field terminal or two? IIRC, the GMs use B-circuit, AKA P-type regulation where the regulator modulates the positive side of the field, so they can use an alternator with a single field terminal -- the other side of the field is case-grounded internally. If you have a single-terminal unit you might have to drain it, pull the cover and check the internal field ground.

If you send me the alternator part number I might be able to find the specs for field resistance, and you could ohm it out -- that would tell you for sure.

-Sean
http://OurOdyssey.BlogSpot.com

luvrbus · March 21, 2012, 12:45:51 PM

Thanks guys, Sean the ground may be the problem the alternator was just rebuilt by a guy in Kingman he may have not knew what he was doing it sure acts like no ground and Dan I have tried your method didn't change a thing lol

bevans6 · March 21, 2012, 01:00:32 PM

My MCI manual says the field current should be around 6 amps, that means the field coil should be in the 4 ohm range. You should get a reading in the under 10 ohm range, if it's open or dead short, then the field coil may have an issue. I don't know how the alternator would put any voltage out if the field coil was open or shorted, the thing wouldn't excite, I don't think. The regulator should be putting a voltage around 24 volts out to the field coil terminal, what is it on yours? I'd swap in a regulator, personally.

Edit to fix a backwards logic trap...

Brian

luvrbus · March 21, 2012, 01:32:06 PM

Brian, I am getting the reading in the 4 ohm range

bevans6 · March 21, 2012, 01:46:30 PM

What voltage is it when running?

luvrbus · March 21, 2012, 02:21:31 PM

32 volts to the field when running,I know how to check it Brian I need to know the cause lol 90% of the time it is a ground problem and I have tried everything on this one

bevans6 · March 21, 2012, 03:14:47 PM

Is there a relay to switch the +ve sense lead to the regulator? (MCI has a "field relay"). If the grounds are good, if the sense lead accurately tracks the battery voltage, then all it can be is the regulator? Is the regulator sense lead connected to battery itself, or maybe only to the alternator?

Tough one, I would have swapped the regulator a long time ago

Brian

Brian

oldmansax · March 21, 2012, 07:58:16 PM

Clifford, I think Sean is right. I vaguely remember having a like problem on a 4104 (?) probably 25 years ago. It was internally grounded & the rebuild guy screwed it up. We screwed up 2 regulators before we got wise. 'Course they were way cheaper then! LOL

They say your memory is the first thing to go but they lie... LOL. But my memory is gone TOO!

TOM

bevans6 · March 22, 2012, 04:58:13 AM

My MCI manual says the correct reading on the field coil is 3.9 to 4.2 ohms. That is for an internally grounded field coil with only one terminal. If you get the same reading to the alternator case, the chassis and to the ground on the regulator, then I would say you don't have a ground problem.

Brian

rdbishop · March 22, 2012, 05:36:46 AM

Clliford, If the adj. screw isn't adjusting and everything else checks out, could that be the problem?
Richard