battery meltdown, could it cause alternator issues

[CCATLETT1984]

recently the rear battery in my m1008 decided to ground itself to the battery holdown (it wore through the rubber coating) and melted the treminal before I could get it apart. I ave replaced both the batteries with some deka 6tl's that i got with the 2 blazers (i grabbed em before they went to scrap), but I am still noticing harder starts. The truck was running when this happened, do ya think that it could have messed up an alternator or the starter? I haven't checked the voltage on the batt's since putting them in a few days ago, but I haven't been driving it since on the same day one of the oil cooler lines decided to get a pin-hole in it. Got two new hoses from the dealer and noticed that the new hoses have stainless steel hardline instead of the aluminium that the old ones were made of (gee who would have thought).

 

[cranetruck]

Check your battery voltage while the engine is running and supposedly charging. That should give a clue.
The regulator (built-in in the alternator) would most likely get damaged if the positive terminal was grounded while charging. There is no fuse/circuit breaker here.
Even a poor connection will create huge voltage spikes, especially if the battery is not charged and the alternator putting out at the max. These spikes are called "load dumps" and can also ruin other electronic gear hooked up and turned on at the time.
Bottom line is, check your battery terminals from time to time.

 

[mangus580]

The other thing is, these trucks are noted for wanting new battery's in pairs...

Is it cranking hard? or just starting hard?

 

[CCATLETT1984]

Its is cranking hard, and i did replace both of the batteries. I had the batteries tested and charged at the local auto parts store. they tested to within 5cca of there rated specs and that was before charging them ( only took about 10 min. to charge each up to full).

 

[mangus580]

I wonder if one of the cables is no good now? There isnt any reason it would have messed up the starter... but if its cranking slow on fresh batteries, I would suspsect something between the two.

 

[CCATLETT1984]

I replaced the cables that go in between the two batteries, and the one that goes from the first batt to the 12v bus on the firewall. I don't remember how to check cables with a multimeter, could you provide some insight.

 

[CCATLETT1984]

I have tested that batteries with the engine off and while running, they seem with tolerences. When engine is off they both read 12.6-12.8 volts while running they both read about 14.7.

I am thinking that its the connection from the second battery to the 24v bus bar, also I think that the connection going from the "pos" of the first batt two the "neg" of the second batt and then on to the 12v bus bar on the firewall might be getting a bad connection. I am going to clean all of the connections tomorrow and prolly will replace the cable that I suspect. Any other ideas?

 

[CCATLETT1984]

I forgot to mention that while driving the voltage guage is dancing up and down sometimes, other times it will hold steady at about 18-22 volts. When the voltage drops the lights dim on the truck really bad. Its sitting lower than it used to before the meltdown. It sticks and i have to tap the front to get the needle to move, so it might not be accurate anymore. I have a replacement to install, putting in when I replace the dashpad with the one in my basement. Might even do that tomorrow

 

[mangus580]

Sounds like bad cables/bad connections. Possibly a bad connection at the alternator as well, if your lights dim like that.

 

[CCATLETT1984]

thanks for the insight, and BTW the letter is in the mail for you.