We recieved a deicent snow storm yesterday, dumping 6-8 inches of snow. So needless to say, I spent a couple of hours plowing snow early this morning after work. After I finished, I let the truck idle for 5 min or so to recharge the batt and cool everything down.

Left for work this afternoon, and noticed that if the truck was left to idle, or idle down the road, it wouldn't charge. If I gave it fuel, it shot up to 14.3 volts.

Long story short, I poped the hood after work and found that as the grid heaters kicked on and off, the power lug off the back of the alt was glowing red hot, getting brighter as the call for power became greater. Pulled the alt and the power lug, cable and nut are all melted togeather, and the power cable is brittle most the way back to the black square thing bolted to the alt.

I did find the ground cable coming from that black square thing, and while it was tight, i'm sure it needs cleaning. The alt is new, having been replaced only a week ago when I had charging problems before.

My question, what gives? Is this a simple matter of a bad ground and alot of resistance, or trying to draw too much through that little power wire? How can I keep this from happing again?
The plow is an old school western, and the cables for that are hooked right to the batt. This truck has been a plow truck all its life, having a Boss V-Plow on it when I got it. And yes, it was abused something fierce.

While plowing, I did keep the rpms up while operating the plow, as I didn't like how the volts dropped and stayed low for a second or 2 while operating it at idle.

Thanks again for everybodys help/input. All of it is greatly appreciated

 

The crimp on the lug has failed, and has a fairly high resistance. The heat is caused by the current through that resistance, concentrated on the bad crimp. I'd replace the cable. I think the stock cable is too light for the job if you run it hard, as in running electric plow hydraulics.

Unfortunately, the heat has probably done some violence to the alternator itself. It should be checked out and any insulators or connections, including internally, that are damaged dealt with.

 

Yep, thats what happened. I had to cut back at least a foot past the black box to get to wire good enough to solder to. Its a temp fix for now, as I want to run a heavier cable, just don't have the time right now.
Did do some damage to the alt itself, mainly the power stud. The alt guy in town was able to replace that internal part and she's now up and running, even gained .10 volt charging, now charges at 14.46 volts

Whats the largest cable size one can run using that alt setup? I noticed the plastic sheild limits the lug size that can fit, I actually broke part of mine with the new lug, because of the excess material when I crimped/soldered a new lug on.

 

I think Jim Lane recommends 2 gauge. I would concur. You can trim the plastic crap out of the way.

120 amps through 6 gauge is ridiculous in my book.

 

Knowing little about the electrical side of these trucks, I thought the draw during the start up event did not route through the alternator?

 

No, not directly. They do, however, draw more than the alternator puts out, so the alternator has much more time at max output recharging the battery than it would in a gasser. That's why when you put frequent high loads on the system, ie plow hydraulics, they will burn an end off once in awhile.

6 gauge wire, assuming each end crimp is the equivalent of 1' of wire (a generous allowance by the way), the 5' length would have a 0.332V drop and dissipate 40 watts of heat at 120 amps. 2 gauge would be 1/3 of that, ie 0.1V drop and 13 watts dissipation.