M923a2 no start

[trooper632]

Hey all, Got a M923a2 in great shape the other day RRAD rebuild in 1-07 and has 420 hrs since rebuild. Problem is it wont start on its own with out Slave cable. Batteries are all 09's, i know they are old but 2 of them have over 12 volts on em and the other 2 have 10.7 volts. truck has a solorgizer on it and the volt gauge shows it charging in the green while running. Is it possible that two of the batteries are bad or should i look for something else. I am going to pull the 2 lower volt batteris out and try fully charged ones to see.

 

[M35A2-AZ]

You need to check the voltage when you try to start it and see if they hold the voltage.
But I would say they are bad. You can use two group 31's or 27's and it will work just fine in the south.

 

[trooper632]

is there a scematic on here somewhere showing how to hook up just two batteries instead of 4

 

[Suprman]

The control box could be going bad it is the black box next to the washer fluid bottle. It doesn't take too much to crank over the 8.3. Turn on the power switch with the ignition switch off watch the battery gauge do it a bunch of times see if the battery gauge shows the same reading each time with a bad control box the relays or contacts are worn and don't always fully engage.

 

[Suprman]

I would make sure all the battery terminals are clean and tight and check the connections on the starter. Rebuild is a loose term in the military.

 

[trooper632]

All terminals on starter and batterys are very clean and tight, it fires right up if the slave cable is hooked up, just wont even attempt if not hooked up

 

[Suprman]

Disconnect the 2 low batteries it will start with just one pair of 12v. See if it cranks. If yes then the 2 bad batteries were dragging the other set down if no then it's probably the control box. The solargizer is more a maintainer than a charger.

 

[Tornadogt]

It sounds like just bad bad batteries... just because they show 12V don't mean there good or hold any cranking amps... I run 2 regular diesel truck batteries with no problems .. just make sure the small 12V+ wire goes on the first battery's in series Positive post..


I picked up 2) 08 RRAD trucks not to long ago and 1 had 2 bad batteries and the other had all 4 bad...

 

[M35A2-AZ]

is there a scematic on here somewhere showing how to hook up just two batteries instead of 4

I have not seen a scematic on SS. But I would just hook the two batteries up in series. then put the heater 12v tap in the center of the two batteries.

 

[wreckerman893]

I picked up a wrecker for a fellow member last year and the batteries would not crank the truck. Since I have two twelve volt chargers I set them up in the cab and slow charged all four batteries for a few days. The truck has not failed to crank on the first try ever since.

 

[Reckless]

If you take them to Oreillys or an auto store like that, they have a machine that will load test the batteries and see if they are good and or can be saved. Oreillys will trickle charge the batteries free of charge (not sure about the other stores though).

 

[DJones]

 

[212sparky]

I bought a load tester from harbor freight. I test them in my truck. Wish it did 24 volt to check the alternator but oh well.

 

[RetiredNavy]

Have it load tested and have the tech determine if there is a bad cell.

 

[trooper632]

My battery charger says two of them have an internal short and wont take a charge so i guess they are going to get replaced. I will try to put two other in from another truck just to be sure, but I think i will just run two batterys in it

 

[trooper632]

Pulled out the two batteries that my charger said had an open circuit short and just hooked up the other two batteries in series. flipped the battery switch and volt gauge popped up in the yellow, hit the starter switch and it started right up. Truck has two solargizers wired in it now I am going to take one out since I left one hooked up to the set of batteries and put the other one in a different truck. Will probibly do this to my other 5 tons since I dont need 4 batteries to start them. Thanks to all for the help.

 

[M35A2-AZ]

Glad two of the batteries came back to life.

 

[Karl kostman]

When I got my 925A1 it had 4 batts that looked brand new, after about 3 months the truck would not crank over, I charged the batts and tried again and still same problem. The batteries all tested out fine all putting out over 12 volts, the only way I finally figured what was good and what was not was to load test each battery, I found two of the 4 were shot. I hooked the two good ones up and used it that way for a few months and that worked fine and this Spring I replaced the two old ones with two big new ones all has been fine ever since! Dont waste to much time testing voltages, go directly to a load tester it will tell you all you need to know!
KK