Batteries draining randomly

[carter262]

1987 M1028
24 Volt
Doghead relay fix
Electrical is unmodified
Both alternators and batteries replaced in the past two years.
Only thing added was a radio that is wired to only come on when the truck is running. I.E. no power to it when the truck is off.

Okay, Truck runs fine. When running shows in the green on the dash. Neither of the Gen lights comes on when running. Every once in a while you will go to start it and the starter is dragging due to weak voltage. Jump start it and it fires right up. I have checked the grounds and looks good. Before this last time it happened, Saturday, I went through the wiring and checked all the outputs on the alternators and they were correct. I am at lose. Any ideas.

 

[cpf240]

Blackout drive light on? Very hard to see in the daylight, and can drain the front battery over time.

 

[carter262]

Blackout drive light on? Very hard to see in the daylight, and can drain the front battery over time.

Thanks for the good suggestion. That is an easy one to over look. I believe though that it is the back one draining. you can put a charger on the front battery over night and it still will not start. That is why I believe that it is the rear battery.

 

[Warthog]

You may have a bad battery.

Also sometimes the alternators are to blame. Either the trio-diode or the rectifier are the culprits. Unplug the 2-pin connector and see what happens overnight. Try each individually.

Buy a battery load tester and the next time it drains check each battery. Harbor fright has one for $22
http://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html

 

[carter262]

You may have a bad battery.

Also sometimes the alternators are to blame. Either the trio-diode or the rectifier are the culprits. Unplug the 2-pin connector and see what happens overnight. Try each individually.

Buy a battery load tester and the next time it drains check each battery. Harbor fright has one for $22
http://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html

View attachment 570360

Thanks. I know I have had the alternator problem in the past. I just hate thinking one could be bad after a year or two. I did have to replace a battery, rear one, once when this happened because it reversed polarity. Since the problem has happened a few times over the years I was thinking that there has to be something that may be causing it. Unless alternators just go bad often now. Which could very well be the case.

Thanks. I am going to try and make time to work on it tomorrow when I get off work.