Had a bit of an emergency, Electrical mystery disaster of sorts.

[rivercreek]

Well, I've been called out to plow for VDOT this evening and a truck of mine (M923A1) has decided she wants to sit this one out.. I've lost every gauge with the exception of the tach and both air gauges. I've also lost the blower motor. I can smack the PCB box (lightly) with a BFH and get them to come on momentarily, but I can't get them to stay on. I know there are many posts on here regarding PCB boxes and their quirks - I've been scanning them as quickly as I can for pertinent info, but everything I've seen so far concerns the A2 variant. I'm not one to ask for "emergency" help typically, but here I am.. I guess my specific request is if someone knows how I can semi-safely bypass the PCB for a couple days to do what I've gotta do with the truck. It doesn't seem as simple as just bypassing the solenoid (I tried that already). Although I'm reasonable handy, I'll be the first to admit I am no electrical guru. Any advice/input would be soooooooo greatly appreciated!! Thanks in advance, I'm havin' a really bad night here...

 

[Swamp Donkey]

Post #21 in this thread deals with an A1 PCB.

http://www.steelsoldiers.com/showth...-Control-Box&p=1615353&viewfull=1#post1615353

 

[rivercreek]

Post #21 in this thread deals with an A1 PCB.

http://www.steelsoldiers.com/showth...-Control-Box&p=1615353&viewfull=1#post1615353

Thanks Swamp Donkey for the quick response - I'm gonna get reading on that thread further. The photos I saw in that post included a circuit board which I do not have. I'm attaching a photo of mine for reference - just in case someone has an epiphany - cause I sure aint...

 

[Swamp Donkey]

Hopefully it'll get you back going. I've never done it but I had that post stashed away in case I ever had to. The solenoids are common and can be replace fairly easily so that might be another quick fix.

I was in the same boat when I first got my truck, but luckily I didn't have profits on the line like you do now. Good luck.

 

[rivercreek]

Hopefully it'll get you back going. I've never done it but I had that post stashed away in case I ever had to. The solenoids are common and can be replace fairly easily so that might be another quick fix.

I was in the same boat when I first got my truck, but luckily I didn't have profits on the line like you do now. Good luck.

Well, I did the jumper procedure (Used an old PCB plug instead of jumper wires) and it did work to start the truck as explained. However, I still have no gauges. My question is - what are these two green wires and are they the reason I've got no gauges? They were originally to the solenoids. Any ideas on that?

 

[The HUlk]

Well, I did the jumper procedure (Used an old PCB plug instead of jumper wires) and it did work to start the truck as explained. However, I still have no gauges. My question is - what are these two green wires and are they the reason I've got no gauges? They were originally to the solenoids. Any ideas on that?

What are the green wires connected to?

 

[The HUlk]

When you jumped pin C to pin D power was supplied to wire 5 (pin D)which provides power to the heater switch and gages. However there is a circuit breaker (fuse?) inline before these devices. If the circuit breaker is open it would cause your symptoms.

 

[rivercreek]

One goes to signal terminal on bottom solenoid, one goes to signal terminal on top solenoid. I'm not even certain that these two green wires are the source of my no gauge/no fan issue (They aren't numbered/labeled like others in the wire harness)- I can make the truck start and run just fine, even with the old (bad)PCB box, I just can't get gauges or the fan. I even tried jumping each green wire individually to 24+ using an inline 5A fuse just for the **** of it with no result.

 

[The HUlk]

One goes to signal terminal on bottom solenoid, one goes to signal terminal on top solenoid. I'm not even certain that these two green wires are the source of my no gauge/no fan issue (They aren't numbered/labeled like others in the wire harness)- I can make the truck start and run just fine, even with the old (bad)PCB box, I just can't get gauges or the fan. I even tried jumping each green wire individually to 24+ using an inline 5A fuse just for the **** of it with no result.

I believe your problem is the circuit breaker I mentioned. I think it's in the dash wiring but have never seen it, know of it from the wiring diagram. You can temporarily run +24v to pin E (wire 27B) on the large diagnostic connector above the passengers feet under the dash to get the heater & gages working until the circuit breaker problem is solved. Fusing that supply may be a good idea in case there is a short which may have caused the the circuit breaker to open in the first place.

 

[The HUlk]

The open circuit breaker would also cause the front axle lamp to not illuminate and no ether function.

 

[rivercreek]

Hulk, I was able to follow your advice and jump 27B with a fused jumper directly to 24V+ and get all my functions back long enough for me to get through this messy storm. I'll dig into it further once things settle down a bit. I can't thank you enough for taking the time to help me through this - I wouldn't be up and running now without your advice. I had to quit messing with this truck last night to do some minor wrenching on another truck, just got back to it late morning today. If you were a girl (I'm assuming you're not with a name like Hulk) I'd give you a big sloppy wet kiss. Perhaps I should re-think that, because if you ARE a girl with a name like Hulk I believe I'd have to settle for a handshake. Here's a couple pictures from the big storm a couple weeks ago just for the heck of it. I've got some pretty cool plowing videos from that storm I'd like to post - haven't figured out how to do that yet. Files are too big.. Anyway, another day.. Thanks again Hulk, you're a life saver!

 

[swede69]

these guys are the best !!!!!! nice help with NO BS

 

[porkysplace]

It looks like you need to keep a spare PCB or 2 on hand since your running it commercial and can't afford down time.

 

[The HUlk]

It looks like you need to keep a spare PCB or 2 on hand since your running it commercial and can't afford down time.

Keeping critical spares on hand is always a great idea. Failures always seem to happen at the worst possible time. I do not believe the PCB box is the problem in this case. I believe a fuse or some other conductor is broken and when he struck the PCB box the shock would cause the broken conductor to make momentary contact.

 

[The HUlk]

View attachment 608442View attachment 608443View attachment 608444Hulk, I was able to follow your advice and jump 27B with a fused jumper directly to 24V+ and get all my functions back long enough for me to get through this messy storm. I'll dig into it further once things settle down a bit. I can't thank you enough for taking the time to help me through this - I wouldn't be up and running now without your advice. I had to quit messing with this truck last night to do some minor wrenching on another truck, just got back to it late morning today. If you were a girl (I'm assuming you're not with a name like Hulk) I'd give you a big sloppy wet kiss. Perhaps I should re-think that, because if you ARE a girl with a name like Hulk I believe I'd have to settle for a handshake. Here's a couple pictures from the big storm a couple weeks ago just for the heck of it. I've got some pretty cool plowing videos from that storm I'd like to post - haven't figured out how to do that yet. Files are too big.. Anyway, another day.. Thanks again Hulk, you're a life saver!

A handshake would do fine lol, glad to hear youre back in business. I know the snowplowing business is feast or famine and glad you didn't miss the opportunty to pay the bills. When you find that circuit breaker, or any of the other ones, let me know where they are and post up photos if possible. Thanks.

 

[juanprado]

The circuit breakers are on the firewall in the engine compartment in front of the driver.

 

[The HUlk]

The circuit breakers are on the firewall in the engine compartment in front of the driver.

Thank you sir!

 

[The HUlk]

Here's a couple pictures from the big storm a couple weeks ago just for the heck of it. I've got some pretty cool plowing videos from that storm I'd like to post

Nice photos, just post up videos to youtube and paste the links into a post. I'd like to see them. I'd love to get a snowplow attachment for my M939, I didn't know they existed.

 

[The HUlk]

The circuit breakers are on the firewall in the engine compartment in front of the driver.

I just had a quick look on my M931A1 and couldn't find them? Do they move around with different versions? And what do they look like? Are they buried in harnesses? I'm looking for the one for my horn circuit in particular.

 

[MWMULES]

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