M923A2 Won't start... All the lights work though!

[crolfe1984]

Starting a thread here to get some ideas flowing. Hopefully I'll have time this Sunday to dig into the problem a bit further.

So I go out Friday (12-19-14) around 2300 to start & warm up my 1990 BMY M923A2. I flick on the battery switch, turn the ignition to run and nothing. No clicks, no buzzer, no warning lights. Not a sign of life comes from the truck. Turning it over to start did absolutely nothing.

Now prior to this I had it running on Wednesday (12-17-14, just 2 days ago). It started like a champ and drove fine. That morning i also verified that the batteries were putting out just over 24v. Other than a 10 degree F drop in temperature nothing was changed or done to the truck. it remained parked.

Interestingly enough my headlamps, turn signals, hazards, and rear flood lights all turned on and worked perfectly. The dashboard lamps too worked when switched on.

I plan to go through sections 0006 and 0088 of TM 9-2320-272-23-1 and see if any voltages up front are off. Anyone have an experience such as this one?

 

[juanprado]

Make sure you are in neutral on the tranny. Neutral safety switch will not let you start in gear!

I know I had to get used to the pattern at first as you natural reflex is Park to the top but there is no park........

 

[crolfe1984]

Make sure you are in neutral on the tranny. Neutral safety switch will not let you start in gear!

Very true! Now I did indeed make sure it was in neutral. That I'm sure of.

Question at large though... When shutting off the truck I leave the the shifter in neutral. Once shutdown is complete I move it to 1-5 where it sits until I go to start next time (moving it back to N of course). This won't cause any undo harm will it?

 

[juanprado]

I don't think it will hurt anything but I am not sure as I always leave it neutral.

I had a similar problem and went through the tm trouble shooting step by step until I got to check the shifter/neutral safety and had a duh moment..........

 

[R Racing]

You could have a shorted battery. Happen to me more than once. No current to turn the engine over but had 24v

 

[1 Patriot-of-many]

Could be the starter switch.

 

[Scar59]

Load test your batteries, cold could have zapped one of them. If they check good, give the PCB a love tap or two.
double check the transmission selector. If you park it in gear the cold could stiffen up the safety switch so it remains open.
Let us know what you find.
JC

 

[Swamp Donkey]

Do your gauges work when you turn on the battery switch? Your voltage gauge should read and the fuel gauge should show the current fuel level with the battery switch on, even with the truck not running.

If they don't, then I'd verify the PCB is working correctly after checking the other things listed above.

 

[goldneagle]

If you need a replacement control box i have used ones for sale. Just PM me for details.

 

[mcmullag]

I showed my M923a2 to two different former army mechanics and they both noted that the PCB usually has dents and hammer marks from being beat on.
I would try a wack on the PCB as one experiment. just my two cents....

 

[R Racing]

Thinking back. My m35A3 did that to me a few times. Ended up being the power on switch was bad. Try cycling it off and on a bunch of times then try starting it.

 

[cwc]

If you are not getting gauges on, then it sounds like PCB or the Battery switch or related connection.

This seems to come up about once a week...maybe it should be a sticky.

http://www.steelsoldiers.com/showthread.php?113634-Ever-see-inside-the-Protective-Control-Box

Chris

 

[Floridianson]

Hope you get it figured out. I allways keep a OTC remote starter with me when I am out or at the shop. As long as you have battery and motor is correct then I can get them fired up atleast.

 

[crolfe1984]

UPDATE

So I went out tonight with tools in-hand to take a crack at this thing. I should note it was just as cold as it was the night it failed to turn (about 36 degrees F). First I made sure the batteries were still putting out 24v. Indeed they did - multimeter confirms just over 24v. I then took a look at the ignition switch to make sure there were no loose wires or connections. That was good to go. Then I made sure the gearbox was in neutral, and gave a healthy whack for good measure. Decided I might was well try and start this thing up.

IGNITION. The green monster turned over like it was 85 and sunny out. I let it run for 20 minutes to warm up and took it out for a test ride. Started and stopped the engine many times and no issue. I can only conclude that either the neutral safety switch was stuck (and now its not) or the PCB magically reset it self on the past 48 hours.

Thank you all for the quick input! Definitely not the first time I've received words of wisdom here and I know it certainly won't be the last.

 

[Scar59]

If you did not touch the PCB, it was most likely a stuck safety switch. Glad you're making smoke.
JC

 

[Swamp Donkey]

Glad to hear you got it going. Still curious whether the gauges were working when it was dead. This will tell you if it was the neutral safety switch causing the problem or something else.

 

[crolfe1984]

Glad to hear you got it going. Still curious whether the gauges were working when it was dead. This will tell you if it was the neutral safety switch causing the problem or something else.

If this happens again I'll surely take note. As I'm not 100% sure what caused this it's a bit unnerving that it may happen while I'm out and about (instead of happening when it is safely parked).

 

[infidel got me]

If I were you I would take a oh crap tool/parts kit in truck until you find problem.

Maybe you got lucky with banging on the shifter, but you really don't know.

Hopefully that was it. I know a breakdown is unforeseen, but if you are prepared

for it, it makes life a lot easier. Keep us posted and don't get the gremlins wet.

Good luck

WILL

 

[crolfe1984]

If I were you I would take a oh crap tool/parts kit in truck until you find problem. Keep us posted and don't get the gremlins wet.

Solid advice. I've already got a few wrenches, including a big 1.5" adjustable, in the cab.

I might do a search on here for a thread for the ideal emergency/road-ready tool kit and put something a bit more comprehensive.

 

[Swamp Donkey]

If this happens again I'll surely take note. As I'm not 100% sure what caused this it's a bit unnerving that it may happen while I'm out and about (instead of happening when it is safely parked).

If it happens again and the gauges don't work, turn the fan on to high and see if it works. The high setting is 24v and runs through the PCB and the low setting is 12v and doesn't run through the PCB. If it doesn't work on high but does work on low and your gauges are not working then I'd be looking at the PCB.

Hitting the PCB box or flipping the Battery switch repeatedly will usually get you back going like you found out with the safety switch...at least for a little while. A couple of other symptoms of a bad PCB are charging problems and ABS faults. If the alternator doesn't charge, the batteries will run down. The ABS system is voltage sensitive and doesn't like low voltage so it sets off the ABS light. If you start having a lot of random electrical issues pop up start looking at the PCB instead of the safety switch.

Not trying to push the bad PCB diagnosis but since you don't know the problem I'm giving you some simple things to check next time it happens so you can rule out one or the other. It can be hard to follow the trail of symptoms back to the PCB if you weren't already looking there.