Smoking wires and alternator SOLVED

[Curtisje]

So 3 weeks ago I started working on the rearend of my M1028A2.

M1028A2 rear end project

I put new used tires on all the way around and now I have a wobble of sorts. I put the rear axle on stands and had my wife run it up to 30mph so I could check it out for out of round tires. The right rear outer tires is either out of round or slightly off center. Easy day. I can fix that by...

www.steelsoldiers.com

I got it all back together and went to start it and it's dead. I mean dead... 1 volt per battery on the meter. I've left this truck sit longer than this before with no problems.

I put each battery on a charger overnight. Next day the rear battery shows 11.8 but drops to 2 v once I load test it. The front battery is still on 1 volt. They are well within warranty so I exchange them for new batteries.

I hook them up. Front battery positive, rear positive, rear negative and finally I touch the front ground cable and the blue wire off the 24v block on the firewall starts smoking. I pull it and watch the drivers side alternator spew smoke as well.

Looks like this project is far from over. At least the alternator is still under warranty too but I'll have to dig into the wiring diagrams and figure what's going on.

 

[nyoffroad]

So 3 weeks ago I started working on the rearend of my M1028A2.

M1028A2 rear end project

I put new used tires on all the way around and now I have a wobble of sorts. I put the rear axle on stands and had my wife run it up to 30mph so I could check it out for out of round tires. The right rear outer tires is either out of round or slightly off center. Easy day. I can fix that by...

www.steelsoldiers.com

I got it all back together and went to start it and it's dead. I mean dead... 1 volt per battery on the meter. I've left this truck sit longer than this before with no problems.

I put each battery on a charger overnight. Next day the rear battery shows 11.8 but drops to 2 v once I load test it. The front battery is still on 1 volt. They are well within warranty so I exchange them for new batteries.

I hook them up. Front battery positive, rear positive, rear negative and finally I touch the front ground cable and the blue wire off the 24v block on the firewall starts smoking. I pull it and watch the drivers side alternator spew smoke as well.

Looks like this project is far from over. At least the alternator is still under warranty too but I'll have to dig into the wiring diagrams and figure what's going on.

"I hook them up. Front battery positive, rear positive, rear negative "
It's not clear to me but if you hooked them up pos to pos that's not correct, I don't think that would smoke the alt. but I'm not going to try to reproduce your test results!

 

[cruzer747]

I hook them up. Front battery positive, rear positive, rear negative and finally I touch the front ground cable and the blue wire off the 24v block on the firewall starts smoking. I pull it and watch the drivers side alternator spew smoke as well.

Sounds like you put the batteries in parallel rather than series (if it is a 24v vehicle still)

 

[Curtisje]

No gentlemen, I did not hook up the batteries in parallel. I hooked them up in series as designed, as always.

 

[MarcusOReallyus]

That smoke means you have a short circuit somewhere. Smoke = short.

 

[Curtisje]

That smoke means you have a short circuit somewhere. Smoke = short.

Yup, I get that. I'll be taking the alternator to the shop tomorrow to see what they say about it. I'll also be checking all the wires involved to include the blue 24 volt wire coming off the firewall. Even though it doesn't appear to have anything to do with the drivers side alt it was also smoking. It is possible a pack rat chewed up some wiring over the last 3 weeks. I found an almost dead one near the truck recently. I thought the cat got it but maybe it was chewing some wires and got bit by the 24 volt.

 

[Curtisje]

The 24v blue wire off the firewall goes to the output side of the pass alt. I'll be replacing that in the morning. The drivers alt spit out the smoke but the wires all seem ok. I may just go ahead and replace them all anyway,not that tough of a job. I'll see what the alt shop says in the morning before I hook everything back up and try again. I have spare alternators sitting around.

 

[Curtisje]

The gentleman at the alternator shop had zero insight for me. I don't think he wants to speculate. They will rebuild the alternator regardless. Now to clean a few things up and start testing wires with the volt meter to be sure I'm getting the right voltage at the right places.

If anyone reading this has any expertise with this alternator please chime in and let me know what part within the alternator itself could have failed and caused the short within the alternator.

 

[Curtisje]

Some day this will become a lesson learned. I installed another alt on drivers side but tied up all wire connections. I also tried up the repaired blue wire on the firewall that goes to pass alt. My plan was to hook up batteries and check for proper voltage to driver alt. When I hooked up the batteries the pass alt went up in smoke. I'm stumped. I haven't found any wiring that was wrong. I've driven the truck for 2 years with no alt issues.

 

[MarcusOReallyus]

Diodes don't like reverse polarity. They go to Smokesville. That's a prime suspect.

 

[Curtisje]

Without hooking up either alt I can turn on the ignition and get all the right responses minus the gen lights and the volt meter; seatbelts buzzer comes on, wait light, glow plug solenoid activates.

I still don't have a clue so I'm hesitant to hook up the spare alternators.

 

[Curtisje]

Diodes don't like reverse polarity. They go to Smokesville. That's a prime suspect.

Well the alternators must have put themselves on backwards one night after a party. Everything else seems to work fine. I didn't rewire anything.

I get what your saying but I haven't changed the alternator wiring. I've checked for that even though nothing has changed since I drove it 3 weeks ago.

 

[Curtisje]

At least I rebuilt the fried fusible links on both alternators before I hooked it all up again. Looks like my packrat buddy probably chewed on the started cable and get a good shock. I hooked it all up. Connected the cables. Switched the 24 volt battery disconnect and immediately saw the sparks BELOW gen2. I shut it off but things were shorting in the alts again. Fusible links are fried. At least I know what to do next.

 

[antennaclimber]

Sounds like the passenger side alternator is no longer an isolated ground unit.

Looking at the schematic, if the passenger side negative terminal is ground, it is possible to have the results you have described. Ensure that the suppressor on the alternator has not shorted to ground either electrically or mechanically.

Use an ohm meter to ensure that the Negative terminal does not have continuity to ground.

 

[Curtisje]

Thanks for the input. Problem solved. The starter wire was shorting on the frame and burning out the alternators. Don't ask me how but that is what was happening. Luckily I have a surplus of used CUCV alternators laying around. Once I found the short on the frame and fixed it I got 2 good alts mounted. I fixed my fused links. Hooked up the batteries... no smoke. Turned on the key... gen1 & gen2 lights on. Started the truck. Revved the engine... gen lights out, charging on the high side of green.

Problem solved, problem staying solved.

 

[antennaclimber]

Thanks for the update.

 

[MarcusOReallyus]

Yeah, I'm not super impressed with the way Chevy routed their wires, especially the high-current wires. That's why I went through and sleeved them with wire loom. Cheap and easy.

Glad you found it!

 

[Curtisje]

Yeah, I'm not super impressed with the way Chevy routed their wires, especially the high-current wires. That's why I went through and sleeved them with wire loom. Cheap and easy.

Glad you found it!

It has a wire loom on it now!