Alternator / generator problem again

[tkgvz]

He is my situation. Bought a gl truck back in August. Determined that alternator was bad ( almost burned up). Replaced it. Turns out that its charging at around 26.7 volts. Today I noticed a burning plastic type of smell and touched the side of alternator and its screeching hot. Does not look discolored and I did not see if it were still charging but I don't think it should be that hot. If you left your hand on it for more then two seconds you'd get burned is how hot it is. Any ideas? Thanks.

Ps I hate electrical problems.

 

[Suprman]

Maybe a short somewhere in the wiring? There really isnt that much to trace in the truck. You can download the P2P wiring guide it makes it really easy to find electrical gremlins. Look at all the starter connections make sure nothing is loose or rubbing on anything else. How are your batteries?

 

[tkgvz]

I guess the only way to check the batteries is to unhook then all from the 24 volt pattern and check them individually. I prolly do that tomorrow as well as check voltage at alt. I wonder if you found a bad battery or two you could just use two good ones to make the 24 volts and go from there. I duno. I let the truck cool down for two hours and started it again and kept my hand on the alt and in about 1.5 min it was back to hot as heck. Thanks tho superman. Can you send me a link for that P2p wiring guide?

 

[Suprman]

Me and linking do not get along. If you type p2p in the google search box it will come up though. You can divide the batteries by disconnecting the center cable on each and see what voltage each is at. Should be 12 and change resting.

 

[tkgvz]

Roger that. Don't think the bearings are bad because no squealing and housing heats up too fast. Hope it's not the copper insulation because this mega bucks unit just came in the mail from memphis equipment. I'll search that diagram and test the batteries too. Good idea with just unhooking the bridge wire. That will definitely make it easier to check all four. Gracias.

 

[ichudov]

Get a Hall effect DC Ammeter and measure the current going out from the alternator. See if it is excessive.

 

[tkgvz]

the alt that i got from memphis has 3 bolts for connections along with an attached pig tail. looking at my connections i have the ground wire hooked up to the top largest bolt. next is the positive from battery or starter. then is the pig tail which i hooked up to existing plug. and the bottom bolt i hooked up the only other wire. i believe this to be the 566 wire which i have no clue where and what it does. do i need all these for proper operation? when i get over there this afternoon i will put the fluke multimeter on it and see whats up. ill prolly take belt off too and turn by hand and see if the bearing is problematic. then check batteries. then if still no luck put it at the end of the driveway with a for sale sign on it..... hopefully not, just frustrating...

 

[Suprman]

The tm shows diagrams and what gives where. Measure the voltage at the alternator with it running, then measure at the +battery connection they should be the same. The ground on my alternator is off to the right if you are looking from the front. The positive is covered in silicone and under a metal cover with 2 screws. I know it can be frustrating it takes a little time you will get through it don't give up yet.

 

[tkgvz]

chudov, the alt was putting out an excessive amount of volts. 36 to be exact. truck off i got 26.9 volts at the batteries. did not check them individully yet. but yes the alt is putting out way too many volts. i unhooked wire 568 which i found to be the circuit that senses system voltage and excites the alt field which caused the volts to go back to normal but im sure this is because the alt was not making any juice and i was just reading the battery voltage. one thing that is strange is that after unhooking this 568 the truck started way easier and much more in a snappy manner. with this 568 wire hooked up it seemed that the starter had a tougher time and it just seemed like there was big load on the electrical system while trying to start. whatever is going on with this 568 circuit is the culpret i think. i will pan thru the tm's once again and follow this 568 wire. suprman, thanks for the encouragement, im hanging in so far. i appreciate all yalls ideas.

 

[rrrr]

The protection control box has relays that work in conjunction with the alternator. I recently replaced my alternator because of low output and the loss adjustability. I received two military replacements one for a deuce with a 3 wire hookup, not correct, and the other a used takeoff for a 939 series truck that was dead.

So I decided to change over to a civilian type alternator. Do a search if you want more info. Anyway, after installation, only a two wire hook up, everything seamed fine but every once in a while it would go full charge ? Doing a shutdown and restart would correct the problem. Finally one morning the truck did it again. At idle it would be fine then rev the engine a little the voltage would go way up. So I took a stick and banged on the protection control box and problem solved. I know there are a couple of relays in the box that help control voltage and a few other functions. I replaced it Friday and everything is working great.

 

[juanprado]

Just changed mine yesterday on a nhc 250 using the stock alt. Under the cover goes 2 wires on threaded studs. The wires are all different size ring terminals and easy to identify. The ground is the largest and bolts to the outside case with a 1/2 nut. The positive is the next biggest inside the cover with a 7/16 nut. There is also a small wire with a ring terminal that goes into the inside smaller bolt with a 3/8 nut. They are held in place with a plastic insulator and 2 screw plate. The wires inside the cover are supposed to be siliconed and sealed after assembly. The other wire hanging out with the Packard connector goes to a separate wire with its mate.

There should not have been any wire on the bottom bolt. Alt takes 4 wires. It definitely should not be hot. Voltage regulator on the back end panel can be adjusted via a pipe plug. I hope your regulator did not get fried.

 

[tkgvz]

Wire 568

Has anyone ever routed wire 568 which sends electrical voltage to the alternator and causes excitation to some other connection to by-pass the pcb box? My alternator is making excessive voltage and as soon as I unplug this wire the alt cools off but doesn't make any juice. I was thinking about finding a 24 volt source and connecting it to it thinking there is something going on inside the box. And how important is the starter protection relay? Is it just a protection so you don't hit the starter switch by accident or has there been a situation where the starter has been engaged on its own without hitting the switch.

Thanks for y'all's patience.

 

[73m819]

Has anyone ever routed wire 568 which sends electrical voltage to the alternator and causes excitation to some other connection to by-pass the pcb box? My alternator is making excessive voltage and as soon as I unplug this wire the alt cools off but doesn't make any juice. I was thinking about finding a 24 volt source and connecting it to it thinking there is something going on inside the box. And how important is the starter protection relay? Is it just a protection so you don't hit the starter switch by accident or has there been a situation where the starter has been engaged on its own without hitting the switch.

Thanks for y'all's patience.

The pcb turns things on, I would look at the regulator on the back of the alternator, if your over charging and getting hot, the pcb will have nothing to do with this issue other then turn on/off the exciter, a seperate hot wire WILL cause the same issue.

 

[juanprado]

One of the functions of the pcb box is to protect against reverse polarity when something something is hooked up wrong. On your previous alt post, which wire did you hook up to the bottom of the alt wrong?

Could be that the volt reg is bad (blew due to the miswiring) or the pcb box is now toast? The alt could also be fried.

check the 23 series of tm's for the m939 as they have real good trouble shooting flow charts. I find them better than the 24 series.
available here:
http://www.jatonkam35s.com/jatonkaM939seriesTMdownloadpage.htm

 

[tkgvz]

Thanks for the link. I'll check it out. I do not think I wired anything wrong in the alt. when I bought truck the pcb box was bad and the alt was cooked from the git go. I have replaced both and thought I hooked up alt the way it should. I read a TM and hooked up the ground wire to outside big post. Next under the cover was the positive post to which the positive larger gauge wire from starter and battery. Next was the 568 wire which was already attached to alt and just plugged into existing plug and the last post is the 566 wire which is for the starter protection relay. The alt came from memphis equipment and the guy who actually rebuilds them told me he tested it on a test bench and seemed very informative. Name was Tim I believe. He was the one that told me to try and hook it up to another 24 volt source incase the pcb box was messed up.


So is there anything I can do with the regulator? I know there is an adjustment on it to either turn down or turn up voltage but with it pushing out 36 volts I feel that something else is wrong. But in the brighter side the fellow at memphis said I could send him the one I got back and he'd try sending me another. But if any of you ss guys that are very savvy with electronics and live near northern va I'd be glad to work some sort of deal to get this problem solved once and for all.

 

[juanprado]

The voltage regulator is available on ebay and directly from the source Southern Automotive Wholesalers $50-$70? They sell the alt and all the parts.
http://www.southernautomotive.com/catalog/product_info.php/cPath/25/products_id/101

There appears to be 2 styles depending if it is a early model with pin connectors or spades. I would suspect you have spades.

If They are willing to swap the unit, it might be worthwhile if you determine it is the regulator. I don't think the adjustment would be that out of whack if they bench tested before shipping.

Sorry, I mis-read your post on the wire. I thought you had a wire in the wrong place.

I have no knowledge of the other wiring procedure they are recommending?

The flow chart for the pcb will let you know if that is ok?

Best of Luck with everything! ( luck is sometimes a vital ingredient )