It's alive!!!

[Thunderbirds]

Well, it had to happen at some point... I believe my PCB box went out yesterday.

Without any previous symptoms, yesterday tried to start. Cranked for for 10 seconds, no start, filled the garage with white smoke. For some reason I even watched the trucks' voltmeter and no voltage drop or rise, even though the wait light came on for 7 seconds. Waited for 90 seconds and cranked again for 10 seconds, then a hesitant start. But much more white smoke. Ran into town, started up every time with the hot engine.

I believe my PCB gave up yesterday. This morning I went out and confirmed with a digital voltmeter, even with the wait light on for 7 seconds, no power to the plugs. Plugs are about 5 weeks old.

Is there any way to tell which version box I have just by looking at it from the outside? I know its one of the older, it doesn't have the diagnostic port.

I read posts for bypassing the plug controller, posts for DIY repairing, posts for others offering to repair, and then posts for upgrading to the newest box and TSU but that gets expensive.

What are the options that make the most sense, are there any more troubleshooting steps? I will get into the T/S part of the TM tonight, just thought to poke here first.

Thanks all.

 

[TOBASH]

Read my signature line for ways to fix and improve it.

Schematics are posted. Feel free to PM

 

[Thunderbirds]

Read my signature line for ways to fix and improve it.

Schematics are posted. Feel free to PM

I started on that thread a while back, but until I actually get into the box itself, most doesn't make sense in my noggen. I will be removing the box and opening in the next few days, maybe do some multimeter probing. I would reach out in the next few days via PM with tons of questions. Thanks for the offer!

There aren't too many other problems that could lead to this, could there be?

 

[Mogman]

I started on that thread a while back, but until I actually get into the box itself, most doesn't make sense in my noggen. I will be removing the box and opening in the next few days, maybe do some multimeter probing. I would reach out in the next few days via PM with tons of questions. Thanks for the offer!

There aren't too many other problems that could lead to this, could there be?

If you let the magic smoke out it will not be hard to find the problem, likely a FET or two with big holes it them, that is a really old box so its time was due.

 

[Thunderbirds]

If you let the magic smoke out it will not be hard to find the problem, likely a FET or two with big holes it them, that is a really old box so its time was due.

Depending on what happened, feasible to repair, bypass or replace is my guess?

 

[Thunderbirds]

Right now I am completely baffled and am asking for a sanity check. I have completely disconnected both batteries, all 4 terminals, and wanted to make sure all power is dissappated before I remove the PCB. To do that I flipped the start switch to run, and the brake light is on

What is happening? Where is this power coming from? Mind you, it's not a full 24V bright, but still very bright, even under the garage light very visible

 

[Mullaney]

Right now I am completely baffled and am asking for a sanity check. I have completely disconnected both batteries, all 4 terminals, and wanted to make sure all power is dissappated before I remove the PCB. To do that I flipped the start switch to run, and the brake light is on

What is happening? Where is this power coming from? Mind you, it's not a full 24V bright, but still very bright, even under the garage light very visibleView attachment 932169

.
So... About 12 hours later.
Is the light still on?

Even a "cap" would have drained itself by now.

.

 

[Thunderbirds]

.
So... About 12 hours later.
Is the light still on?

Even a "cap" would have drained itself by now.

.

I couldn't tell you, once I saw that I continued to remove the box for more T/S. As soon as I disconnected the under dash connector and tried the switch again, the light did not come back on. So I assumed it is a capacitor powering the system and not a "ghost" exciter. That gave me pause and I didn't break open the box for inspection, just because vehicle electronics are foreign to me and I hated the idea of discharging that via my body.

I then reinstalled and reconnected the box just to see if any wires were lose, but no-go. Still no voltage drop, the wait light comes on for the 7 seconds or so, much smoke during the first start of the day. Once the truck ran for just even a few minutes, it fires right up within one second so I know the other systems are working ok.

There are a few avenues one could go, I am not sure yet how I want to go ahead. Manual push button, Camo box, new KDSS.

Life is throwing me for a loop, so it may be a few weeks before I get back to troubleshooting and fixing. Still open to ideas or suggestions.

Thanks!

 

[Thunderbirds]

.
So... About 12 hours later.
Is the light still on?

Even a "cap" would have drained itself by now.

.

I couldn't tell you, once I saw that I continued to remove the box for more T/S. As soon as I disconnected the under dash connector and tried the switch again, the light did not come back on. So I assumed it is a capacitor powering the system and not a "ghost" exciter. That gave me pause and I didn't break open the box for inspection, just because vehicle electronics are foreign to me and I hated the idea of discharging that via my body.

I then reinstalled and reconnected the box just to see if any wires were lose, but no-go. Still no voltage drop, the wait light comes on for the 7 seconds or so, much smoke during the first start of the day. Once the truck ran for just even a few minutes, it fires right up within one second so I know the other systems are working ok.

There are a few avenues one could go, I am not sure yet how I want to go ahead. Manual push button, Camo box, new KDSS.

Life is throwing me for a loop, so it may be a few weeks before I get back to troubleshooting and fixing. Still open to ideas or suggestions.

Thanks!

 

[Mullaney]

I couldn't tell you, once I saw that I continued to remove the box for more T/S. As soon as I disconnected the under dash connector and tried the switch again, the light did not come back on. So I assumed it is a capacitor powering the system and not a "ghost" exciter. That gave me pause and I didn't break open the box for inspection, just because vehicle electronics are foreign to me and I hated the idea of discharging that via my body.

I then reinstalled and reconnected the box just to see if any wires were lose, but no-go. Still no voltage drop, the wait light comes on for the 7 seconds or so, much smoke during the first start of the day. Once the truck ran for just even a few minutes, it fires right up within one second so I know the other systems are working ok.

There are a few avenues one could go, I am not sure yet how I want to go ahead. Manual push button, Camo box, new KDSS.

Life is throwing me for a loop, so it may be a few weeks before I get back to troubleshooting and fixing. Still open to ideas or suggestions.

Thanks!

.
You may want to open the box and look at the "board" down in the bottom. It could be that a capacitor was "blown" off that board. Maybe. Maybe not, but definitely worth an investigative look...

 

[mow***com]

There are a few avenues one could go, I am not sure yet how I want to go ahead. Manual push button, Camo box, new KDSS.

Life is throwing me for a loop, so it may be a few weeks before I get back to troubleshooting and fixing. Still open to ideas or suggestions.

Thanks!

I remember being at this crossroad with my M1123 and chose to just use a new KDS smart start.
Back when I worked on little Mitsubishi Mighty Max/Dodge Ram50 trucks.... The 2.3 turbo diesel had a voltage reduction glow plug system at 12/6 volts.
I can't recall if I was missing a few things, or wanted simplicity. But, remember bypassing it and just wiring a momentary switch to a solenoid, powering the glowplugs. In the 5+ years that I owned it, I can't remember a single problem with it.
You just have to be smart enough not to hold your switch for too long.

I never favored the idea of having two sets of glow plug wires in the engine bay. That is the only way I have seen it done in a HMMWV, due to the box.