Help for a new m936 owner please...

[nayrbrellim]

Bad pcb. Smack it with a hammer if you need it to work.

Rebuild it afterwards.

It's the black box behind the washer bottle on the drivers side of the engine bay.

Pcbs go on the fritz during hot and cold snaps in weather generally

Fuel vents won't cause any issue like you had. Especially broken

Where in TN are you?

I actuallty had my PCB go bad, incredibly enough hitting it with a hammer works, well for a little while.

 

[The FLU farm]

Alright, resurrecting an oldie here as I'm not sure what's the least dumb thing to do next.

M936 A1 with ABS (or at least the sticker) that one day had a completely unresponsive dash when turning that battery switch on. It clicks under the hood, lights work, etc., but dead dash.

Bonked the box somewhat lightly with a small hammer, resulting in that the the warning lights lit up, the shrieker made a muted noise, the fuel gauge woke up, and the volt meter moved up a needle width or two.

Removed the box and activated the solenoids with a small 12 volt battery. The bottom one sounded perfect, the top one a bit lame. Cleaned the corrosion off the easily accessible posts, plugged the box back in...back to nothing (could have been a bad ground to the box).

So here are my questions after watching Simp's videos: Do I need the electronics on the board in this application?

Do I need the second solenoid? I don't need functioning ABS.

Could I simply wire in a single 24063 solenoid and mount it outside the box, or maybe even leave the box off altogether?

Any words of wisdom will be appreciated as I need to move this one to access a trailer.

 

[IronGiant5Ton]

Alright, resurrecting an oldie here as I'm not sure what's the least dumb thing to do next.

M936 A1 with ABS (or at least the sticker) that one day had a completely unresponsive dash when turning that battery switch on. It clicks under the hood, lights work, etc., but dead dash.

Bonked the box somewhat lightly with a small hammer, resulting in that the the warning lights lit up, the shrieker made a muted noise, the fuel gauge woke up, and the volt meter moved up a needle width or two.

Removed the box and activated the solenoids with a small 12 volt battery. The bottom one sounded perfect, the top one a bit lame. Cleaned the corrosion off the easily accessible posts, plugged the box back in...back to nothing (could have been a bad ground to the box).

So here are my questions after watching Simp's videos: Do I need the electronics on the board in this application?

Do I need the second solenoid? I don't need functioning ABS.

Could I simply wire in a single 24063 solenoid and mount it outside the box, or maybe even leave the box off altogether?

Any words of wisdom will be appreciated as I need to move this one to access a trailer.

View attachment 937300View attachment 937301

FLU Farm, I just had this exact issue happen to my truck. My box circuit board shit the bed. I tested the old solenoids and they ready 55ohms on ne, 25 ohms on the other. Correct for continuous and intermittent solenoids.

In short, I'd wire 2 solenoids in the box even if not using ABS to prevent further issues down the road. I used 2 Cole hersee 24063 solenoids and the original box. No diodes inbetween.

If you need to start it just to move it temporarily you can jump "D" and "C" in the wiring harness, disconnect the electrical line on the same side as that box that goes to the fuel cutoss solenoid and touch negative and positive on the starters solenoid. You just won't have gages.

My circuit board looked like a resistor and a diode got way too hot and fried out.

I just got it rewired and started it up today no problem.

 

[The FLU farm]

Thanks! I ended up doing the very same thing (in here waiting for the liquid electrical tape on the new wiring to dry) hoping it'd work. Now I'm confident it will.

One thing I did differently was to modify the box a bit. basically cut the end of the lid where the connector goes off of the box and welded it to the base. That way the lid can be removed without disturbing the connection, should a 24063 stop working. Also haven't looped the yellow wire like you did. Should I, and if so why?

When testing the OE solenoids the top one had a much fainter "click", and no continuity. Anyway, I'll post some photos when the new paint on the box has dried.

 

[IronGiant5Ton]

Thanks! I ended up doing the very same thing (in here waiting for the liquid electrical tape on the new wiring to dry) hoping it'd work. Now I'm confident it will.

One thing I did differently was to modify the box a bit. basically cut the end of the lid where the connector goes off of the box and welded it to the base. That way the lid can be removed without disturbing the connection, should a 24063 stop working. Also haven't looped the yellow wire like you did. Should I, and if so why?

When testing the OE solenoids the top one had a much fainter "click", and no continuity. Anyway, I'll post some photos when the new paint on the box has dried.

I looked the yellow wire because its a sensing line from the alternator. I have a Brushless aftermarket alternator which is wired in differently from the OEM. therefore, kinda useless.

 

[The FLU farm]

Put the lid and base on top of the furnace for tonight, to hopefully cure the paint quicker. As you can see, I didn't spend any time making it look good, but it should work.

Drainage holes by the connector small enough to keep insects out, but should be enough to vent the interior and avoid the corrosion that was present in the OE box.

Had the same ares blackened on my circuit board, by the way.

 

[The FLU farm]

Alright, ready to install.

With some luck it'll even work.

 

[IronGiant5Ton]

Alright, ready to install.

With some luck it'll even work.View attachment 937740

Good luck! Keep us updated!

 

[The FLU farm]

Okay, this has me wondering.

The batteries in this 936 have always impressed me, staying at around 28 volts for months. Figuring that they deserved some attention after some two years I added water in most cells, as needed, then had them on a solar charger for several days, combined with desulfation units.

Those Canadus desulfators shut off when the voltage goes below about 13 and I liked seeing that they stayed on for many days after having disconnected the charging. They were still on when I switched to a single 24 V desulfator from PulseTech that I'd received.

That one stays on no matter what, but according to PulseTech the 12 Volt version only draws 0.010 Amps.

It was a couple of days later that I tried starting the engine and found the dead solenoid in the PCB. Yesterday I reinstalled the "new" PCB, had power to the dash...but no start. Checked the battery voltage and it was down to 23.1. Apparently that's not enough to crank a 250 Cummins.

To me it's odd that the voltage was suddenly so low, and also that it wasn't enough to turn the engine over. The batteries are charging (at 10 A) today, and once (if) they charge up I'll load test them. Each one measured about the same voltage. The obvious suspect is the new PulseTech unit, but I've always had good luck with their products, including the other 24 V desulfator I've had for almost a year.

If I'm lucky the Cummins will fire up later today. In real life I'll be trying to figure out why it didn't start.

 

[IronGiant5Ton]

Okay, this has me wondering.

The batteries in this 936 have always impressed me, staying at around 28 volts for months. Figuring that they deserved some attention after some two years I added water in most cells, as needed, then had them on a solar charger for several days, combined with desulfation units.

Those Canadus desulfators shut off when the voltage goes below about 13 and I liked seeing that they stayed on for many days after having disconnected the charging. They were still on when I switched to a single 24 V desulfator from PulseTech that I'd received.

That one stays on no matter what, but according to PulseTech the 12 Volt version only draws 0.010 Amps.

It was a couple of days later that I tried starting the engine and found the dead solenoid in the PCB. Yesterday I reinstalled the "new" PCB, had power to the dash...but no start. Checked the battery voltage and it was down to 23.1. Apparently that's not enough to crank a 250 Cummins.

To me it's odd that the voltage was suddenly so low, and also that it wasn't enough to turn the engine over. The batteries are charging (at 10 A) today, and once (if) they charge up I'll load test them. Each one measured about the same voltage. The obvious suspect is the new PulseTech unit, but I've always had good luck with their products, including the other 24 V desulfator I've had for almost a year.

If I'm lucky the Cummins will fire up later today. In real life I'll be trying to figure out why it didn't start.

You know what's crazy... my batteries shit the bed the day before I attempted to start it and found the PCB to be faulty. In my truck, there's 2 12v AGM 900CCA batteries. One was at 0 CCA the other at 600. I had them both charging for a day or so and got them both up to about 850CCA. That seemed to do the trick. I'm not a battery wiz but I know enough to have figured this out.

Do you have a battery tester for a regular car? Like an OBDII with a battery test function? I wonder what kind of CCA's your batteries have.

100% worth the investment if you don't have one.

I'm in CT and my vehicles have been having a hard time starting in 10° weather.

 

[The FLU farm]

Got the batteries to a full charge today, but was running out of daylight by the time I was able to get to this issue. Bypassed doing the load test and tried starting it.

Everything looked good on the dash, and after turning on the ignition. Hitting "start" made it sound like low batteries and the starter might have turned the engine a 1/4 turn. Consequent tries were worse or slightly better.

Tried the desulfator on a pair of fresh Group 31s and in 24+ hours it hasn't drawn them down more that 0.1 V, so I declared that one innocent. For tomorrow's adventures I plan on doing a load test and bypassing the solenoid. Well, in my case bridging it since that's easier than undoing the connector and connecting C and D there (if I remember the letters correctly).

 

[The FLU farm]

Okay, now I understand why it won't start.

Load tested the batteries and the two "end ones" (positive and negative for 24 V) failed miserably. Not sure I've ever had a battery make the needle go to zero that quickly. Oh well. Now the question is; what happened to those two?

Connected a 24 V solar charger to the jump start plug in normal fashion, and then connected a 12 V desulfator to each "end battery". Also disconnected a smaller gauge wire that was attached to the negative post of the positive "end battery" (it's still connected in the photo). No idea what that wire is for, but at least it can't affect the system now.

While I get that batteries go bad, and when connected to each other can bring the whole set down, in this case the other two tested very good. Also new to me, there was a faint "crackling" sound when putting a load on the two bad end ones.

It'll be interesting to see what things look like tomorrow. Even with minimal charging (it's overcast and snowing on and off) I'm hoping that testing the specific gravity again will show some improvement. Really don't want to have to buy four new batteries.