Trouble-shooting the Protective Control Box in a 5-ton

Hey all,
I had a starting problem a couple of times at the Aberdeen show. When I flipped the Batt switch to the on position, the gauges would kick on like always. Then, when I flipped the Stop-Run-Start switch to the Run position it would sometimes turn on the CTIS/ABS and sometimes not. Then, when flipping it to the Start position, it would make one hit with the starter and then start kicking the solenoid like the batteries were dead. We got it jumped at Aberdeen and we didn't turn it off all the way home. The next day I tried to start it and nothing comes on when I turn the Batt switch on. The Protective Control Box (PCB) will click, but no gauges move. When I turn the Stop-Run-Start (SRS) switch to the Run or Start position, I get nothing.

Terminal B on the Batt switch sends 12v, yes 12v from the center tap, to terminal A on the PCB. That is working. Then, terminal D on the PCB is supposed to send 24v to terminal B on the ignition switch. It is only getting around 2-3v at the SRS switch, which explains why the ABS/CTIS won't kick on and why it won't start.

I fully charged the batteries with a charger and still no dice. I read another post about similar symptoms in a M813. The post mentioned rebuilding the PCB, but no one ever came up with the article.

The problem is, I am supposed to have the truck at a 5 year old kid's birthday party this saturday afternoon. He loves the military and has been begging his parents to ask me to bring it. I agreed and the kid is stoked so I hate to disappoint the little guy.

I might be able to have one over-nighted here. Anyone have any suggestions on rebuilding it? From the wiring diagram it looks like it provides a 24v feed to the gauges, the alt, the CTIS, the ABS, the starter, the air dryer, etc... so I ain't going anywhere without it.

Thoughts?

Chris, it looks like the "protective control box" is a bit more complicated than the one used in the 809 series.
With a wiring diagram on hand, it would probably be possible to bypass it, pretty sure the simpler 809 box can be.

Check the status of the "neutral start" switch, wires 498 and 499.

I have not actually climbed up on my five ton yet, but I do know that John Winslow has the control boxes for less money than the other dealers... I have also heard that the 900 series box will work on a 800 series truck, but not vice-versa. It has been suggested to me that I get a spare.
AMGeneral has experience working around these...

Whats the NSN...... I think I have one of these boxes sitting in my stash of stuff........


Ziggy

I might have one also, get the NSN posted.

According to the 272-20P it is 2590-01-144-8674

to tell the truth this sounds like the main power selenoid, mine sticks every now and then, if no gages ,ect come up when the main on/off switch is fliped, i flip the switch a few times and it is ok,, not sure if its all in the pcb or seperate

The NSN is 6110014442546 PN is 12450333. I have flipped the heck out of it back and forth a hundred times and still nothing. The numbers came out of TM 9-2320-272-24P-1.

Sorry, I dont have one.

I showed this thread to Sarge at work (he just got back from Iraq a couple months ago) and he said to double check the ground on the control box. He then said that they had a truck in his unit that was mission ready only three months out of twelve due to control box problems, that it would get fixed, then die, etc... He then said that a Sargent from a unit based in Germany that was tasked with fixing thier stuff (starting near the end of his tour) had figured out a common thread to the failure mode for these things, and thus, a repair/avoidance fix, but could not remember what it was.
I think that he has contact info for him though, so he's scratching his head some more on this...

Hope you get it fixed Chris.

Chris, The fuel pump has a manual setting. It's on the solinoid where the wire is, at the front. It's a knurled knob. Just turn it in and use a starter button. The engine will start, but won't shut off. You can turn the knob out to shut it off. All this is if it is an 855 cid engine. If it's a C model, just wire the fuel shut off up and use the starter button. To shut it off, un-do the wire.

Chris,

Tap the control box with a metal headed hammer a few times and then try to fire it up. It sounds like your protective control box is going, but you can make it work for a while yet by giving it a few "love" taps, before you fire her up.

Don't worry about screwing up the box, as it sounds like it's on its last leg anyway.

Joe

Chris, if you end up with an extra unservicable unit, I'd like to take a look at it, if you wouldn't mind sending it to me.
Thanks.

Thanks everyone for your efforts and tips! It was dark when I got home last night so I didn't get to check anything out. I will work on it tonight. I'll check the grounds first to make sure nothing vibrated loose coming down I-95, since it is such a smooth road If that doesn't help, then I'll wack on it a bit. If it's still a no go, then I may see if I can get it apart to inspect the guts.

I am afraid to rig the engine to get it to start. The PCB controls too many things. It energizes the alt, the CTIS, the ABS. I don't want to break anything expensive. John Winslow is only an hour from here. If I can't get it going, I'll give him a call and see if he has one. I may be able to run down there in time to get one and get back.

Well fellas, I went out at lunch and wacked on the PCB with the BFH After a severe beating (not really) and much clicking from On to Off, the gauges finally kicked on! I switch the SRS switch to Run and the CTIS and ABS lights lit up. I flipped it to Start and the ol' 8.3 clattered to life! I let it run for a bit to see if it would charge. I checked the starter solenoid lug and got around 29 volts so I'd say it was in high-charge. Looks like I'll make the Birthday party after all. Also looks like I'll be buying a new PCB from Winslow. He loves to see me coming, right John?!

Good news. The PCB worked again this afternoon and I made the little boy's Birthday party. He said it was the best party ever. Even better than the blow-up Jupiter Jump. It's fun to make folks happy with your big green iron. Thanks again gang for helping me get on the road.

I hope to take my PCB apart later this week or next to see what makes it click! If I get a new one, I'll pass the old one on to you Bjorn for your inspection.

Thanks Chris, I'm always a bit sceptical about fancy electronics, especially when so much depend on it. A by-pass procedure should be available, even if it means disabling an important(?) feature such as the CTIS.

I'm glad the birthday party was a success.

A lot of electrical problems lead to the ground on the trucks and getting a good bond to the ground. Used to work on Boeing Jets in Everett ,WA . We had a meter to check the bond on grounding lugs we installed . A good bond to the ground makes things work like they should , a bad bond to ground gives headaches!