2nd Gen Non-Engine/Transmission Charging system getting lazy (going south?), did my winch kill the altenator?

[Coalsmoke]

I've noticed the last few months that my charging system seems to be lazy. It still works, but I am only reading 10-11 volts or so at idle after starting the truck, and to get it up to where it is charging in the 13-14 volt range I need to rev the truck to 1500-1800rpm range. So, its not completely dead but it has me really worried as I tend to make heavy equipment service calls to remote locations. I tested each individual battery, and they are fine, and I disconnected the grid heaters and they are not sticking on, so that leaves the PCM with the voltage control circuitry inside of it and the Altenator. I am really hoping its the altenator and not the PCM. What I am also wondering is if my 9000lb Warn winch (which can draw upwards of 400amps) killed something when doing a heavy winching one day, because as a general rule I always run the truck when winching, but then I was talking to a couple of tech people (one majoring in electronics and whom I trust quite well) and they told me that this could be dangerous for the Altenator because whatever power at 12volts that the winch cannot get from the batteries, it will try and suck from the Altenator. So, I'm wondering A. is it likely to be my altenator that is dead and B. what can I do to prevent killing it or anything else next time I use my winch?



Thanks guys

 

[BK]

You may have popped a diode on one of the phases.

Either check the diodes yourself or take it to a parts place and have it tested.

I've run winches off of less powerful alternators and have not lost the alternators... but it's always a possibility that you'll smoke out a bad diode through such an acid test.



The alternators also don't put out full capacity at idle. They will take some rpm.

But with the heater grid disconnected you should be above 12. 6 after a few good minutes. . it will take a bit to charge the batteries up after cranking.



The other thing to, is that the charging system is controlled based on temperature. A lower float voltage is called for from the computer when it's warmer out. Higher when it's colder out. (And most of the country now is seeing much warmer temperatures).



Your in a gray area,. . hence why if you saying the charging just ain't what it use to be and you most definitely see a difference, you may have taken out a diode... . which will reduce capacity a bit.



If you need to replace the alternator , look for an aftermarket one with 200a +.



The alternators are suppose to protect themselves, be current limited based on impedance. . but as I said above, you always have a chance of smoking out a weak diode. . it happens even without winching.

 

[San Felipe Bob]

Alt. Brushes

Check your Alt. brushes.

I thought it was my PCM.

Turned out to be worn brushes.

It acted just as you describe yours.



SFB

 

[Coalsmoke]

You guys, I really appreciate the accurate help, thank you. After reading the first reply I decided to pull it apart, and sure enough, one of the soldered leads going to one of the 4 diodes was burnt right through and black, looks like it really got cooked. Also, the brushes were worn a good 1/8" into the commutator, and they were at the very end of their life. I was really surprised as the bearings in that Denso sounded like they were still in good shape. It has been my experience before that they go before brushes etc, and I didn't know about the diodes. Needless to say I decided to go get a new Bosch 120A unit, comes with a Lifetime warranty, Oo. Thanks again guys, very much appreciated.



BTW, why would D/C go through all the trouble to make the PCM that varies voltage depending on the temperature. It makes sense that in colder weather the grid heaters would be on more and need more charging capacity, but why cut the current down for the summer?

 

[BK]

The batteries... ...

At hot temps, for them to have a longer life,they want a lower float terminal voltage. Heat is an enemy of the battery. Even during discharge.



At cold temps, capacity of the battery is lost, I forget the temp, but at one point the capacity is about 1/2. So to obtain a reasonable charge, to have a reasonsable capacity, at cold temps, to get the capacity, they need a higher float terminal voltage.

 

[Coalsmoke]

BK, thanks for the info, that's a new one for me but it makes sense. I guess that PCM isn't so bad after all. Should I be concerned that the old diode burnt out? In terms of some sort of fault causing the new diodes to burn out like that, or is that what they do when they turn to smoke?

 

[BK]

Not a problem, past life , for 15 years I designed all sorts of battery chargers for all sorts of different types of batteries for military and telecom applications.



It could have even just been the connection to the diode that went south, and got all carbonized... . that happens too. If the connection got hot enough, the heat could have fried the diode too. Is the actual connection in much worse condition than the body of the diode?



Mud / dirt / water-corrision could have been to blame if it was just the connection.

 

[Coalsmoke]

The screw tap connection on the block that holds the 4 diodes looks fine, but the wire is burnt right were it enters the diode, and as a result no longer enters the diode b/c it is burnt through. Both wires going to this diode look black and burnt, only one burnt through, the diode body itself doesn't look too bad, but it is hard to tell because they are all sort of enclosed in a casing.

 

[Coalsmoke]

Just put the new altenator in and everything is back to normal. The old one was quite dirty, like you suggested. I was thinking though, my fuel shutdown solenoid died a couple years back, so i put in the manual shutdown cable, which means I can have the truck running but the ignition turned off. Now, I have never noticed anything happen after doing this, and even some times I would would run it for 5 or so minutes with the ignition off and I never noticed any adverse effects, but I'd like to just check here for peace of mind that it wouldn't be that which possibly hurt the diodes. Thanks again for lending you expertise, if you ever have welding questions feel free to hit me up