1986 M923 intermittent no-start condition

[IsaLandr]

I just wanted to update that this thread hasn't been forgotten or ignored. I haven't had a chance to do much on the M923 yet. Some things in real life came up, interfering with my ability to get out there and work on the truck. I did get the lower connector chiseled open, so that's a start. And the PowerProbeIV arrived, so I've got that now.

We'll see if this weekend proves any more viable than last weekend for getting things done on the truck. I'll need to stock up on wasp spray... the yellowjackets seem to think the cab of the truck is an ideal nesting location, I have to chase them out of there and knock down at least one new nest every time I open the truck.

 

[Bill Nutting]

Hi guys, I'm not hijacking this thread, but I have a similar problem with a friends M934 (1987 with ABS). This truck has demons in it! The original symptom was, when we turn the battery switch to on, the starter starts cranking (run, start switch is off). Also no gauges or lights. After replacing the battery and start switch problem continues. So I'm attempting to trouble shoot the wiring using the diagram above. here are a few questions so far:
Where are all of the battery connections shown on the drawing? Example: 81, 81A, 6B, 81B, 569A, 15 These are shown all connected together in the diagram, but I can't find these connections anywhere. Wires 5A and 10 show an arrow to "circuit breakers". I have no idea where these circuit breakers are. There are also a lot of wires going to "STE/ICE" I don't know what that is (maybe a harness connector somewhere). Just to clarify, I spent 51 years reading schematics and wiring diagrams. These diagrams are above my head. I'm not sure why. Please help....
BTW, I forgot to mention that the control box was replaced as well. After reading this thread I will have to check to make sure the correct box (ABS) was installed. Wes, if you see this post, I may need to order one of your rebuild control boxes to carry on my truck for a spare part.

 

[IronGiant5Ton]

Hey guys, my 923 just decided to not show battery power in the dash gauge. Checked both batteries and they're both at high 12v and high 800s for CCAs. I flick the battery switch, nothing but dash lights, the blower works and headlights work. I read through a bunch of your knowledge and ripped my PCB off and apart. Turns out I have the circuit board one. But different from the one posted in this thread.

I was wondering if anyone had pictures of a pcb with the 2 Cole hersee 24063 solenoids in it. I really need this truck running soon. I hate a 21k lb lawn ornament.

 

[IronGiant5Ton]

Here's a few pictures of what m truck had been rocking.

 

[IronGiant5Ton]

I have re wired my PCB without a circuit board and without diodes. Going to throw it in the truck tomorrow and see what happens!

 

[IronGiant5Ton]

I have re wired my PCB without a circuit board and without diodes. Going to throw it in the truck tomorrow and see what happens!

Update, Rewiring as shown in the previous post did the trick! No more starting issues.