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
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. :) )
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!)
;D BK ;D
The adjusting screw does nothing Ed I tried that first this thing is driving me nuts
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)
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 (http://ourodyssey.blogspot.com)
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
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
Brian, I am getting the reading in the 4 ohm range
What voltage is it when running?
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
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 ;D
Brian
Brian
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! ;D
TOM
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
Clliford, If the adj. screw isn't adjusting and everything else checks out, could that be the problem?
Richard
Clifford we had that problem with our old 4905 and it was the regulator when they switched it out they replaced the old one with a new updated model that had no adjustment screw. It was a cheap fix (relatively) and it worked great. The mechanic said that the old adjustable style were nothing but trouble. Funny thing is I think it quit on us in Kingman. Small world.
Rick
Sounds like your alternator is full fielding all the time. Try disconnecting all the field leads and check the output if it is still 32 volts you probably have an internal wiring problem. With no current to the field there should be zero magnetic field and zero output. Check the voltage at the field terminal with all the leads disconnected expect the main battery terminal; you should have zero voltage. If you have battery voltage, you probably have cross connection inside the alternator supplying battery voltage to the field.
Be very careful grounding stuff. The manual says to never ground something which I can't remember after working on it a few months ago when mine was doing weird things.
I think it was the field but don't hold me to that!
Cliff, upon thinking about the results of our testing of that unit, I think that the regulator is not grounded and the regulator is passing full field current to the generator. I don't think that I have ever seen one do that, before.
I'm sorry that I didn't think of that while we we there.
For what it's worth.
Tom Caffrey
OT how did the Jakes work Tom
good luck
My 4107 voltage reg has an added ground wire to the chassis that is not original, so maybe this is a problem?
OT Jakes work GOOD, Cliff.
Thanks.
Tom Caffrey
Clifford, did you get it fixed?