charging/alternator PROBLEMS

[jager07m1008]

ok lets start by from what I can see the wiring on this truck is now what it is suppose to be my problem is that i can not hook up the red/white wire to the right alternator. if i do so i have sparks at the last battery terminal that i hook up and not little sparks. the left alter. is hooked up with red to engine wiring harness block and black to intake ground. then the tiny brown wire to the wire harness. I am not sure what that wire does.. right alter. red to positive teminal block. red and white i can not hook up . i have tried to replace gen # 2 light and i still get no light when starting i took dash apart today and have 24 volts at light bulb connection i did not test the generator #2 relay not sure how and also not sure if the one that is there is the correct one. i have been working at this for 2 weeks now and one step from selling the rocket. if anyone wants to give me their phone number so i can talk to a english speaking human I would greatly appricate that. thank you ahead of time. also if I do not respond right away i may be trying to figure something out THANK YOU

 

[Warthog]

You need to let us know what type of CUCV and if it is still stock or not. Have you replaced the alternator recently?

You have classic problem of a bad passenger side alternator that does not have the "isolated ground". There has been dozens of post on this. Many by me.


Do you have a ohm meter? If so then:

Keep the batteries disconnected, remove the wires from the passenger alternator and check for resistance between the case and the "ground terminal", the one where the red/white wire connects. It should be an open circuit. if it is not then you will have sparks fly when you hook up the batteries.

If the ground terminal has a connection to the case. that is the same as a direct short for the battery.

Check this and let us know.

 

[jager07m1008]

will try tommorrow thanks

 

[Crash_AF]

Guessing from his username that it's a 1008 and sounds like it's still a 24V system.

Did you replace the Alternator in question? If so, where did you purchase it? If it's not a military specific unit, then it's probably a non isolated ground alt like Warthog said and that will cause your direct short to ground when connecting the batteries.

Later,
Joe

 

[jager07m1008]

yes it is a 24 volt system. i disconnected the batteries and checked like you told me to and i had about 13.00 ohms so is this what you think or is that ok thank you again also what is the exact number of the alt. if it is bad so i know what one to get. hey just to make sure the wires are correct the big threaded post is positive the small one is negative nothing else is connected to the alt. thank you

 

[Crash_AF]

If you have 13 ohms between the ground stud and the case, then that is not an isolated ground alternator. Did you purchase the alternator from a chain store or did it come with the truck? The system will not work with a non-isolated ground alternator on the passenger's side. The driver's side is ok, but the passenger's side is not and will throw sparks as you have seen.

If you did get the alternator from a chain store, call them and see if they still have your core. If they don't (or you didn't have one) you need to go get a refund and then purchase the correct alternator from a military vehicle vendor.

Later,
Joe

 

[Warthog]

yes it is a 24 volt system. i disconnected the batteries and checked like you told me to and i had about 13.00 ohms so is this what you think or is that ok thank you again also what is the exact number of the alt. if it is bad so i know what one to get. hey just to make sure the wires are correct the big threaded post is positive the small one is negative nothing else is connected to the alt. thank you

Correct on the size of the terminal posts, big is positive, smaller is ground.

You have the wrong alternator, it is bad or was rebuilt wrong. With only 13 ohms (should be infinite) it is just like laying a wrench acoss the battery posts. The Smoke Genie is released from the bottle.

From the TM 9-2310-289-34p Parts manual, the correct GM part number is 1105500. This is a DelcoRemy 27SI, type 100 alternator that has been manufactured to separate the Rectifier Bridge Ground from case. This is accomplished with some insulated screws and fiber washers. Nothing really special.

Tell us about the alternator. Did you buy the truck with in? Just installed it? What. Where did it come from.

 

[jager07m1008]

well the jersey girl came with that equipment installed when i purchased it . like i said it was rebuilt Dec. last year to so the shop has been very good so far now this but i am sure it will be fixed is there any other possible causes that would cause it. thanks again i will be taking it off this week and geting the alt.. repaired i will let you know how i make out thank you

 

[Warthog]

It is very possable that something inside the alternator broke and is allowing contact between the electrical and the case. It could be as simple as the fiber washer broke. The alternator rebuild/repair is covered in the Tech manual and has been posted many times.

Make sure you download the Tech manuals and study the wiring diagrams. All the wires that hook to the alternators are covered. You will need to look at two different diagrams.

Good luck with the repairs.

 

[jager07m1008]

well i took the alt to the shop and the man took it apaprt in front of me by looking at the pics and what i saw there isn nothing wrong with it he also tested it . so i have to believe that this is correct and i have some other PROBLEM. so i came home and hooked it up and well no spark at battery when i connected the cables but as soon as i started it the wire where the fuseable link was hint hint now was burning. so there was no link there and now there is no wire either. so what can you tell me know. also i still do not have a gen 2 light when starting. also what is the correct number for the relay for number 2 generator. i am not sure that it is good it looks new. thinking maybe idiot before me had problems and replaced it any ideas would be great. THANK YOU

 

[Crash_AF]

The relay under the dash is a 12V Bosch relay commonly used in automotive applications.

If the alternator had 13 Ohms between the case and the ground stud, then something was wrong with it. If it did not have any Ohms between the ground stud and case after he reassembled it, then the problem is solved. If it still has any resistance other than Infinite (open) then there is a problem with the alternator as used in this application. It would be perfectly fine in a 12V vehicle, but it will not work in a 24V system on the passenger's side.

Which fusible link are you describing as burned up?

Later,
Joe

 

[jager07m1008]

joe the fusible link that is connected to the red and white wire coming out of the pass side # 2 gen. that goes up tp the firewall. so let me get this straight the ohms select to ohms touch red probe to terminal and black probe to case. correct. also are both relays the same under dash. hey by the way how does this all work with the positive out of one gen to the neg out of the other. thanks again

 

[Crash_AF]

Yes, both black relays under the dash are the same.

The theory of operation for 24V is just like the batteries themselves. If the alternators are wired in parallel (Pos to Pos, Neg to Neg) you get 12V with twice the capacity. If the alternators are wired in series, (Pos to Neg) the system adds the voltage with the same capacity.

Here's a little diagram that I drew up to illustrate the difference.

Lastly, the procedure you describe is correct, one lead to the ground stud, one to the case. Set to Ohms (or the diode check where it beeps). If there is anything other than OL displayed on the meter (or whatever equals infinite ohms or Open Line) current can flow from the case to the ground stud, which means 12V is going to the ground which causes a short circuit.

ETA: the fusible link you blew was the one for the circuit in question. It most likely blew because of the flow through the alternator case which I'm assuming has SOME resistance but it isn't open so instead of a spark show, it was a slow blow.

Later,
Joe

 

[jager07m1008]

hey joe thanks again i am going to try to have another shop check the alt for me since you know so much where is a good place to buy the 27si and don't say auto zone or a store like it. thaks again i will check again the ohms tommorow if weather permits me to do so thanks

 

[Crash_AF]

OD Iron has some, there are also other military vehicle suppliers who occasionally have them. You might be able to get them from GM (Part# 1105500) but I don't know for sure.

A good alternator shop should be able to rebuild them no problem, it's just that most don't understand the purpose of the isolated ground and therefore don't make 100% sure it's truly isolated unless you stress to them why it's necessary.

As an alternative you can do the repair yourself, they are not that hard to work on once you get the pulley pulled off and rebuild parts are cheap.

Here's a PDF manual for the alternator from GM, it gives some tests and troubleshooting information and shows the internal configuration.

Later,
Joe

 

[jager07m1008]

hey joe i could not open that pdf. also i took the alt. to another shop the man checked it out and said again there is notheong wrong so i came home and put it in truck and still got sparks at battery so can i test that diode in the dash or does that have nothing to do with it at all. by the way i check the ohms before i put it in and it read .0004 or something close to that. any other suggestions thanks again

 

[doghead]

Swap your alternators, from one side to the other. See if that solves your issue.

 

[cjtroutt]

Do what doghead said.
It sound like non Ice gr alt for alt 2
most alt & start shops have no idea on ice ground alt 12 & 24V system .
Send me an PM I give my ( PH number to you call me I will explain.

 

[Warthog]

hey joe i could not open that pdf. also i took the alt. to another shop the man checked it out and said again there is notheong wrong so i came home and put it in truck and still got sparks at battery so can i test that diode in the dash or does that have nothing to do with it at all. by the way i check the ohms before i put it in and it read .0004 or something close to that. any other suggestions thanks again

Time to find a shop that knows what they are doing.

If the ohms are anything other that Infinity (multi gazzilions) it is not an isolated ground and will cause sparks. It will work on the drives side but not the passenger side.

Are you comfortable taking the alternator apart yourself?

If so the rebuild is covered in the -34 manual. Section 4-2.

Here some photos that show what the "isolated ground" is. These are the bolts and washers that mount the rectifier. This is the only special item for this alternator. That is the purpose of the "isolated Ground" to "isolate the Rectifier from the case.

They are items #18 and #22 in the diagrams.

I am working on a rebuild writeup but it isn't ready. I rebuilt it for $25 in parts and a couple of hours of time (including taking pictures)

 

[jager07m1008]

ok thanks again i guess i am going to break down and buy a new on thank you