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Got the burb, Got issues with it.

You appear to have a shorted regulator going "full field". (Or other short in the unit allowing full field current flow.) This full field will run the voltage as high as the bats will allow - then they boil dry.
Those small two plug wires are:
1) Kick on and charge lamp. (Possible use as the remote voltage sense as well.)
2) Tach signal wire.

Others you got of the ground (unusual) and the positive charging terminal. Military surplus alternator? Some high output units have the regulators on the back. Worth taking to a good electrical shop for a repair as the extra amp units are very high priced due to burning up windings all the time.
 
This truck is ex FD. The problem is the factory exciter and tach feed are sent back into the cab and then two other wires are connected to the HO Alt. I have to dig around in the mess under the dash to see where the alt harness goes but I would rather just get the factory pigtail nd drop a stock alt back on. The factory alts on these trucks are more than adequate for every day use. It's possible the alt is no good. I know the builder who's sticker is on it and he sucks. He did a couple starters and alts for my oil trucks and I had a problem with every one of them. So if the HO alt is junk it would be much cheaper to put a factory one back on . The tach signal from this HO alt must be somehow converted by some sort of something I have bot found yet under the dash. This truck had all kinds of batt eliminators etc and all of it was butchered during removal so at this point as much stuff I can return to stock the better.
 
Just a thought is it externally regulated? If they rewired then possibly is an external regulator, not uncommon for service vehicle high output alts to be externally regulated. Interesting that when you hook up that fused power wire you full field the alternator probably explains why it was pulled. What are the letter designations on the back of the alternator where the small wires go?

I was watching a 3500 fire truck the other day and it seemed to me that it was set up so that when going to Park it was wired to automatically go to high idle made sense to me that they would do that. Not sure if that feature was always there or if it was activated only when all the lights were on.

Cheers
Nobby
 
I don't know, I'm going to be spending alot of time trying to un mess the wiring in this rig. There is so much spaghetti I need a jar of Ragu. The harness does to to some kind of black plastic box buried deep under the dash. I could feel it but not see it.
 
well after fiddling through the aprts books at GM the little 12 inch or so harness to the alt can be had for a measly 109$. What a bunch of f'in scumbags. I see a day at the junkyard this sat.
 
what harness is it? The stock GM harness? If i venture up to Chuck and Eddies in southington on saturday i'll rip one out for you if you still need it.

Any chance it's a self-exciting alt? I have one here off a OTR truck(Delco 135A 33SI) that's self exciting once it hits a certain RPM.
 
iamdave0887 said:
what harness is it? The stock GM harness? If i venture up to Chuck and Eddies in southington on saturday i'll rip one out for you if you still need it.

Any chance it's a self-exciting alt? I have one here off a OTR truck(Delco 135A 33SI) that's self exciting once it hits a certain RPM.
Click to expand...

That type of ALT set to Kick In at the same RPM as the high idle could be useful as long as it is also regulated. Say for sustaining Big Bright Lights.
 
Acesneights1 said:
well after fiddling through the aprts books at GM the little 12 inch or so harness to the alt can be had for a measly 109$. What a bunch of f'in scumbags. I see a day at the junkyard this sat.
Click to expand...

YIP! I just went and looked at one to replace my Burned out fuse. The local salvage wouldn't pull the part or let me pull the part.
 
Kenny...dont know how much of a hurry you are in, but i may have the harness you need. The cab i picked up a month ago has a complete engine harness (98' 6.5) so im pretty sure i might have what you are looking for. Gonna have to give me some time to check as work has finnaly gotten busy and ive been working late, but if I have one it is all yours.

-Nick
 
I'll pay for shipping and whatever else you want. Not a uper hurry but would like to know that it is my issue so i can move onto the rest of the truck. Gonna hit some local junkyards. I think Gassers may even have the same harness.
 
well, It's charging..:D
I could not find the harness I needed so I had to make it. What a PIA> The gassers use the same plug for the field/exciter but the plug did't have the extra wire for the tach. So I grabbed two plugs and pulled the wire out of one to put in the other thinking that would be easy...NOPE. The gasser plugs are not punched out for the extra wire/pin so I had to painstakingly drill it and then microfile the square out to get the extra pin/wire into the plug but I put it on and the truck charges perfectly and tach works mint. Also PMD skip is gone. Ging to remote mount the PMD today. I will be listing the alt for sale cheap that I took out with wiring and box. I don't know what's wrong with it but when I hooked it up it overcharged but if someone can figure it out it's a pretty cool setup. The alt is huge. I have no idea how many amps it puts out but it uses a 2Ga batt cable to connect from the output side to the batt so I would think over 150 amp. I am sure this was a pricey setup. I'll post pics later.
 
These things can be a real mess when the charging system is not up to par.

Be it grounds or low voltage the issues can drive things nuts.

When the Alternator is not on line the batteries alone can fall short of keeping the computer happy.

Some of the circuits are long and the wires are small. with some years and miles on the clock and likely a ground or two thats not perfect, the voltages can fall off out on the fringes and therein lies the problem most likely.

Glad you got it fixed.

Missy.
 
Here's the pics. There is the HD alt on the ground with harness. You can see the one small harness is from my Dually. I had to take it out to replicate it as I had no schematic.
 

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Glad to see you have it under control now. I looked last night for the harness, and it seems as though a few of the plugs were cut off. And wouldnt you know it.....the alternator plug was one of them. I do have a pile of misc crap he gave me, so theres a good chance it might be in there if you still want the factory plug.
 
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