No start- Bad control box?

[98hd]

Went to start my M818 this past weekend, and got nothing. I flipped the batt switch everything was as normal. Flipped the other switch to start and it wouldn't turn over. The batt gauge went into the yellow, but nothing still.

I thought maybe batt's were really low, so I slaved over my M342 w/ 2 brand new walmart special group 65's. Still same symptoms.

In the past I've had nothing happen when flipping the switch to start, but trying it again a few times and it would start.

So does it sound like a control box? Any way to check the box or bypass it? I hear they are expensive.

 

[DaveP]

Chris, did the batt gauge move when you hit the start switch?
any clicking? cranetruck (Bjorn) did an article on the control boxs i think.
I got a new one off ebay for a spare and it looks like the XM819 is going to need it soon! if you have to use or move it, call me and we can walk thru the bypass method.

 

[98hd]

Chris, did the batt gauge move when you hit the start switch?
any clicking? cranetruck (Bjorn) did an article on the control boxs i think.
I got a new one off ebay for a spare and it looks like the XM819 is going to need it soon! if you have to use or move it, call me and we can walk thru the bypass method.

Batt gauge did move, you can tell it seemed like it was taking a load of some sort. No clicking, except what sounded like a relay when the swtich first goes to start. Nothing like a start solenoid or anything.

I don't need to move it, just would like to fire it up now and then. I just got the new trans, clutch, and t-case in. Didn't even get it the interior or the top bolted back down and now this. Always something.

 

[DaveP]

Might want to start with the easy checks first. loose connetions at batterys, frame ground, starter ground, starter hot lead, starter solenoid energiser wire.

 

[98hd]

Might want to start with the easy checks first. loose connetions at batterys, frame ground, starter ground, starter hot lead, starter solenoid energiser wire.

Yup, I am planning to, just didn't have any tools with me at the time. Thought I'd see if it sounded like a control box first before I screw around out in the cold , I'm sick of winter already.

 

[cranetruck]

The control box houses two 50-amp relays, the first click you hear should be from the one that prevents damage from a reverse polarity condition. That relay will only energize if the polarity is correct (a diode in the coil circuit does it).

Power relays like to switch "live" loads, the always present arcing helps to make a good contact, "dry" switching, like in this application may be a problem.

Also, as posted elsewhere, vent the case to keep moist air from condensing and water from collecting inside. There is a pipe plug by the connector, that should be removed.

Looking at the diagram, you should be able to bypass the the box or part of the circuitry anyway. I haven't looked too closely at that......

 

[cranetruck]

Here is a better view of the circuit diagram. Couldn't edit the above post for image....

 

[98hd]

Here is a better view of the circuit diagram. Couldn't edit the above post for image....

Thanks Bjorn, looks like I will have to study that when I get home.

 

[Army Ed]

or you could try the old army way and wack the control box with somthing similar to size and weight of a kevlar....lol

 

[TedG]

800 series control box

I recently rebuilt one of my control boxes and thought I would pass this information along.

The silver can relay is Stancor 70-903 and can be purchased for around $20 at Allied Electronics.

The black plastic relay is AMTEK SAZ4401 and are becoming harder to find. Since they are used in helicopters, I found a repair shop to source them. $50

The open relay is a Stancor but is obsolete according to my connections. So I swapped it for: Potter&Brumfield T92P11D22-24. This relay is 24vdc and is DPDT though you only need on pole.

I tested the diodes and reused them.

I cut the box open with a hack saw. It was easy. Then I chisled the copper coated steel plate off the box and removed the guts. I removed all three relays since they ALL had high resitance and since I was opening up the box, I decided to replace all relays. It is very important to assemble the unit exactly same way it came apart. I shortened the lugs of the relays to ensure a safe distance from the black box wall. I popped riveted the relays on. It is also important that the copper coated steel plate is grounded to the black box once it is reassembled. I tack welded the plate and then the box end covers and sealed the rest with silcone. All in all it take about 1.5 hours to do the job. I also drilled a 1/16th hole in the brass plug to allow the enternal not to condensate.

Good luck and happy control boxing! I hope this helps!

 

[Armada]

Thanks for posting Ted. You just took all of the voodoo out of the 'blackbox'.
I can also see why it's been suggested to vent the box. There is surface rust buildup on the bottom of the inside of the case.

 

[nk14zp]

Great info Ted thanks.

 

[98hd]

Thanks for the info Ted.

Since I started this thread I figured I would update. My control box was fine. My starter was the issue.

They are not easy to find, and are expensive rebuilt. I found a manual on the prestolite website. Wasn't 100% accurate, but very close. I pulled it apart and started the testing. I thought the switch (forget the name) on top was bad.

I put it back together so I could get a replacement. Only thing I did different is there is a large copper disc that connects the power in to the power out to the starter. It was worn so I flipped it. Once back together I bench tested it and it worked. Threw it back in the truck and all was well once I primped the pump w/ fuel.

Just a temporary fix for now, a new starter is in the trucks future once I get everything else ready for the road. Need to go through the brakes, and hubs, and put a few parts back on that came off w/ the trans swap, and I should be good to roll.

 

[Armada]

Hey Ted. Got into my 'blackbox' today. Thought it might be the cause of my intermittant loss of electrical power and truck dying. I've been operating on the overide thumbscrew for awhile, and when the truck is running I sometimes still notice the gauges will all drop out intermittantly. Well, I split the case on the box to get to the internals. I didn't have to saw it like you did, as it was a different style box. I used heat and then pulled out the sealer used to hold the cover on onto the base.
The internals are different than the one you have shown too. The 2 relays are identical physically. I can read a number on one of them, 24??45 or 05. Maybe a P/N, maybe a date. Truck was refurbed in 2006. Are they the same internally or would there be a need for different values? I see no signs of corrosion or condensation.
I'd hate to pull it apart and replace the relays if they don't need it. They would be very easy to replace except for the fact that they are bonded to the base. I guess I'll clean the already clean ground contacts again and put it back on the truck and try it. Any thoughts?

 

[TedG]

hi paul,
that might be a 900 series box. they work in 800's though. can you check resistance through each contact? intenals might be oxidized. since I can't see well using my phone maybe there is an issue with the pcb .
even 'new' trucks have problems!
ted

 

[Armada]

I'll check the resistance of the 2 relays tomorrow. Here is another part that mounts next to the blackbox on the firewall. Also looks like some knid of relay. It looks the same or similar to the one you have inside of your box.

 

[5_TON_TOMATOE]

I had the same problem when i recovered my 818. Damn thing has 4 batteries, and after charging, when put on a load, 2 of them would drop to 10 volts, and not start, just a click. Seems like the oth er 2 would carry the load, but not. Now I need a cheap source for some batts

 

[cranetruck]

........... I also drilled a 1/16th hole in the brass plug to allow the enternal not to condensate...........

Excellent final touch! Venting is important unless the box is filled with an inert gas...

It's funny how the manufacturer gets away with using "Radio Shack" parts when the box is welded or encapsulated.

 

[cranetruck]

hi paul,
that might be a 900 series box. they work in 800's though. can you check resistance through each contact? intenals might be oxidized. since I can't see well using my phone maybe there is an issue with the pcb .
even 'new' trucks have problems!
ted

Like I have posted before, the reverse polarity protection relay (the one with a diode in the coil circuit) is switched without a load the moment the master switch is turned on, which means that its contacts will build up an non-conducting oxide over time. Power relays are supposed to switch a specified minimum load, so that the oxide can burn off....
A sealed mil spec relay would be a better choice in this application, much less chance for oxidation in an inert gas environment.

 

[Armada]

Ted, Bjorn,
Excuse my ignorance, but electricity is not my forte. I know enough to crawl around with a chaperone, lol.
I tested the resistance on both relays. For puposes of explanation, the control box is positioned in the installed position.
Well, I was going to type the results out but it will be easier to just post some pictures. So here you go..... see below.
What does all this mean? I'm guessing the top relay is bad? What about the values from the center posts?
Next question, if the relay is bad, where can I get a 24v 50a replacement? Is that the relay from Allied you mentioned Ted? Did I see 4 posts on that one? Please help an electrical dummy out. Thanks!