M923A2 Power Problem

[will35010]

I have a weird power problem. When I turn on the battery switch I hear a click in the PCB box, but I don't get any lights on the dash and can't start the engine. At one point, I could flip the battery switch a few times and it would work fine, but now it's not doing anything.

I checked the voltage on the run switch and with the battery switch on I get around 5 volts there and when it magically works I get 24.

I need some help tracking down what's wrong and how to troubleshoot it.

I checked the battery connections and voltage and all the batteries are good with clean connections.

I thought about just replacing the battery switch with a toggle but wanted to make sure that it's the problem before I go to rigging anything up.

We use the truck as a brush truck for our fire department so it's hurting us being down.

Thank you for any help you guys can provide.

 

[goldneagle]

Sounds like the Black Control Box is acting up. If the solenoids inside get stuck or wear out the truck will not start. Try tapping on the box with a hammer or wrench while someone tries to start the truck. It may start but you probably need to replace the Black Control Box.

 

[will35010]

Is there a way to bypass the PCB box? I searched for a tutorial or to see if someone else has done it and haven't had much luck.

 

[will35010]

Nevermind, just found how to bypass it and repair the PCB box here http://www.steelsoldiers.com/showth...-Control-Box&p=1615353&viewfull=1#post1615353

I'm going to try this to make sure it's the problem.

 

[mdemars03]

I don't know of a way to bypass it. There are plenty of people here with way more experience with these trucks than me who may be able to give you an idea on bypassing it but I don't believe you can.

As far as looking for a replacement they are not exactly the cheapest from a normal vendor. There is one that shows for sale in the classifieds right now. It was last updated the first part of January so I don't know if it is still available. It doesn't show it as sold yet so you may want to check it out. http://www.steelsoldiers.com/showth...M939-series)-Power-Protective-Control-Box-100

Also I know a couple members have parts for sale and may have one for you. PM member 98G as he has a truck that is being parted out and may have what you need or know where to find it quickly. Also fuzzytoaster has some control boxes although I'm not sure if he has any PCB's. Both of those guys are extremely helpful and very easy to deal with for getting parts if they have them.

 

[74M35A2]

Yes to all pretty much. You can bypass it, but you would need the vehicle side harness connector to do so, and then you would have to unplug it to shut down, so that would be emergency road side use only. When you hear a click, it is the solenoid pulling in, but the contactors are not completing the circuit anymore, they are worn or dirty. You can rebuild the PCB box with new solenoids, there are several threads here on how to do it. They indicate part numbers, how to get the box open, all that. Check it out.

 

[Swamp Donkey]

Or you can buy them direct from the manufacturer without the "middle man mark-up".

http://www.southernautomotive.com/catalog/index.php/cPath/33?osCsid=c6f67a131bfc13f9cf220a5dd5ebbe9e

Call them for price and availibility if you decide against the other suggestions.