M923 won't start

[patracy]

Not sure what a 939 program is....where can I download?

Try TM ...23-5 Maybe somewhere around Pg 611-612

The wiring Schematic is in TM...23-5 Pg-611+ Remember there is a 569 wire and a GRD A and a #68 wire that connect to batteries as well. My understanding is if the 569 wire is not connected you will have no low speed heater fan. The GRD and #68 wires I believe go straight to the Diagnostic Connector so I "think" if they are not connected you are "ok" . I am in Monrovia, CA

There is a schematic in the back of the TM.

TM 9-2320-272-24-4

In the TM.

Or download the 939 program and have them all on your computer. I worked on my 931 harness today. Super easy to trace things down with the app running.

Probably in the same place that everyone has been telling you to look?

 

[Retiredwarhorses]

Perhaps it would have been more useful to PM me if in fact you have the answers to my Posts? THat is unless you get more
joy from your replies.

 

[patracy]

Ok, so I should PM you a message that says to read the TM? I'll try to lead a horse to water...

At the top of every page here is a link to Technical Manuals = http://www.steelsoldiers.com/forumdisplay.php?95-Technical-Manuals

Clicking that link will give you a breakdown of all the various areas of discussion. Specifically in your case, you're interested in a 5 ton TM. So click on that section.

http://www.steelsoldiers.com/forumdisplay.php?115-5-ton-and-up-TMs

Under that section you'll see threads started that break it down into specific series. You're looking for a M939 series truck. So...

http://www.steelsoldiers.com/showthread.php?79228-TM-s-for-the-939-series-trucks

Now, Doghead already mentioned the TM you specifically need. TM 9-2320-272-24-4 which is:

TM9-2320-272-24-4.pdf (right click save as)

The M939_P2P.zip file is also there as well if you wish to load it.

If you're expecting someone to spoon feed you wire numbers, you're probably not going to get an answer.

 

[Retiredwarhorses]

Well, at this point I have gone through as much of the TSU section on no start that I care to.
truck starts and runs fine as long as it is jumped from the starter.
, just nada at the ignition switch....it's all wired right and I get proper voltages at the PCB connector and switches
as well as checked for opens. For now I might just wire an m35 start button to the starter....I'm thinking its a PCB issue.

 

[Retiredwarhorses]

Does wire 74 go to the starter solenoid post labeled switch?

 

[sandcobra164]

Even though I don't care for you over some comments concerning some training. The most common problem I've found is the wire coming from the PCB to the Starter Solenoid. I've spliced new wire into quite a few of those on the M939 Series trucks. Test by probing the wire coming out of the bottom of the PCB that engages the starter solenoid while an assistant holds the ignition switch in the start position. Probe close to the connector and start probing downward to see where along the run of the wire you lose the voltage. I normally lose it about 10 inches down just before the bend.

 

[Retiredwarhorses]

Problem Solved....Put in a Takeout PCB from another 9XX truck and fired right up....Pretty much what I suspected all along. I guess I should have gone with my gut instinct all along, that and the fact that all my TS revealed no issues anywhere else.

 

[Charlie B]

I'm a newbie and have searched and read every thread but can't find resolution. I have a m923a2 that will not start. I originally had no electrical power, power switch on then ignition switch, no alarm nothing. Took PCB off, opened up and cleaned all connections ( box has black melted plastic all over inside and white powder on inside walls of box). Reassembled box, sealed with silicone, and reinstalled. Now power switch activates gauges and turning on ignition sets air and brake alarm, but will not turn starter. Checked and cleaned all connections ( starter, solenoid, batteries, and under dash fuses). Confirmed shifter in neutral, reset park brake, fine tuned PCB with hammer, turned power switch off and on several times, turned ignition off and on several times. I'm at a loss. A new PCB is $400 and worth it if that is the only thing left but don't wont to waste money if that isn't the cure. Thanks !

 

[Retiredwarhorses]

Replace the PCB.....you can't have burnt anything in that box...you can find them for much cheaper then 400.00
i found mine, a used takeout for 75.00
any 939 series will work.

 

[Retiredwarhorses]

And you can't own these trucks without going through some financial pain...trust me.
it ain't like you can go down to napa and buy alot of the stuff one might need.
but I had your issue and it was a PCB.

 

[Scarecrow1]

I see little was changed since selling my truck . I've been a member for a long while and it is always the same B/S . Guys young and old buy these trucks and find this site looking for answers . Some find help others find insults and some smart ass trying to look good by making someone else look bad . I have a PCB Box Charlie B drop me a Email if you need one . No lectures just help........

 

[Retiredwarhorses]

Did I miss something? Seems its posts like yours that seem to start s**t where none exist....frankly, its only on this site does the mud slinging always seems to happen...dont have this issue on the G503.

 

[cwc]

Charlie B, it sounds like you have made some progress by getting the main power relay to pull in but just need to get the starter to operate. You might want to take a look at the wiring diagram again, figure out what each pin is doing and what is needed to complete the starter circuit (e.g. check the neutral safety switch). BTW, you can replace the individual solenoids inside the PCB. I had one go bad, the main (continuous) power relay. The circuit board was still working OK, powering the coil of the solenoid but the solenoid would not pull in. It turned out that the one permanently mounted (welded) into the box was an intermittent duty SAS-4418. I replaced it with an SAS-4410 rated for continuous duty, $32, easy to find online: http://www.texasindustrialelectric.com/pdf/ametek_relays.pdf .

 

[cwc]

Found a picture of the new solenoid installed in the PCB. Also a picture of the burned-up contacts in the old solenoid.

 

[Charlie B]

I found a new PCB from Boyce Equipment, received it yesterday and installed same. Truck instantly came to life!! Thanks again Steel Soldiers for the advice and detailed posts. This site has been extremely helpful in making resolution to situations!
Thanks Again!!

 

[chevy427]

I have a m923a1 that wont start...no power to the dash every thing is dead...read the threads....replaced the ignition,replaced the PCB it has 2 batteries in it that have 12.5 volts all to no avail....any help is greatly appreciated!