Is this a starter solenoid? Clicks but no power to starter.

Intermittently my M923a2 will not start, flip the power switch and it just clicks near the firewall, no power to start truck. I have got away with toggling on/off over and over and eventually the power comes to life but that does not seem to work anymore.
When I flip on the power this bottom solenoid clicks, (located on driver side firewall under hood. Looks like it has a diode jumping across. I shorted across where the diode is and power came on and was able to start truck, could it be as simple as replacing the diode or the solenoid? If so any idea on the part number or specks for them so I can find and order a replacement(s)
(D on the picture points to the diode and c points to the solenoid that clicks)

I'm not sure, but that may be somebody's home-made deal. Those crimp connectors and different colored wire are not typical of military issue. Regardless, the lower solenoid looks in much worse condition than the top via corrosion, and the small black wire on the lower can seems over-heater at the crimped on terminal. Terminal insulation seems burned black and the wire insulation itself looks split open in the same area.

There is a protection box which supposedly prevents the starer from being re-engaged when the engine is running. It is not fully reliable, and some people do away with it and route the starter switch directly to the starter. Not sure if they are still using the neutral safety interlock when doing so.

I have the same problem. I flip the power on and off until it actually stays on which I can tell because the fuel gauge shows a reading. I ordered a new one from Memphis and hope to get around to installing this week.

That's the electrical control box. It pretty much controls all the electrical.

I've had one apart but ended up just getting a good used one to replace it with. I've still got it laying on the shelf and may tinker with it sometime.

Mine was just like yours but I've seen others that also had a circuit board in them.

Replace the master power switch. 50/50 chance that is the issue. I just fixed one with the same issue by replacing the master power switch. Only mine actually got to where it finally just crapped out all together. The contacts inside break off.

I found online someone with similar problem replaced the lower solenoid with a golf cart solenoid so i ordered a 67020 SPST 24V 100A Insulated Continuous Solenoid for $25 I will replace it first, then the switch and finally just replace the entire box if the first 2 don't work. Thank you all for your help.

The diode is for surge suppression on the solenoid. Don't bridge the contacts, that is just bridging the positive and negative terminals together and will result in more problems down the road.

From my understanding you can put the 939 series pcb in the 800 series but not a 800 series in a 939 series.

Check your starter switch with an ohm meter and see if it is working properly all the time. Check the solenoid manually to see if it engages all the time. That will tell you where your problem lies.

Had the same problem on my wrecker. Replaced the black control box and solved the problem. The contact on the solenoids get corroded and do not make good contact. After a while they get burned from arcing and it goes down hill from there.

Search PCB here and a bunch of info available, and yes those crimp connectors are a correct vendor supplied part. They fail, your same problem starts. Memphis Equip and Erik's has brand new latest update ones available.

Ordered the replacement 24v Solenoid when was taking off the old one noticed the broken ground wire shown in picture, could have tried to just replace the bad wire but already had PCB off the truck and new solenoid in hand. Had to grind off the solenoid mounts from the back side of the box and then used self taping to remound since the holes did not line up. Hooked it all back up, ran new ground wire (the blue one) and she fired right up. Thanks everyone for your help.

Anybody have a schematic for this box?

It's in the -20 all the way in the back.

Search "inside the protective control box"

Thenext44. So this means we can start shipping our noworking box's to you and you will spice them up? LOL

Did you ever try jumping the contacts on the starter with a screw driver? My 923 has been doing this too, I replaced starter switch and that worked for a while, I have banged on the starter and that has worked in the past too, today I banged on it and tried jumping it at the starter and all it does is spin like the starter isn't kicking out and engaging I don't have any idea what to replace but I'm about fed up with it

I have brand new modern gear reduction starters on sale right now. 3 year warranty. Jumping the solenoid large terminals should spin the starter motor but not engage the pinion gear. Check for power on the small wire going to solenoid for +24v when held in crank. Applying +24v to the solenoid small wire energizes the solenoid coil to pull the shift fork and throw the pinion gear out and into the ring gear. Once the solenoid is fully engaged, a copper bar inside the back of the solenoid cap connects both large solenoid terminals together and applies power to the starter motor to spin it. The starter should also have a large ground wire on the back of it as to not pull 600 amps through the engine bearings.

I have no clue what's wrong with this thing, some days it's totally fine, it ran foe a couple hours yesterday, I shut it down and two hours later nothing, didn't do anything with the key, usually a little love tap on the starter will fix this,but it didn't, when I jumped it on the starter it spun but didn't engage, when out this morning and she cranked right up several times. It seems like it does what ever it is doing once it gets hot, but I have no idea

Kvrazelm923 said:

I have no clue what's wrong with this thing, some days it's totally fine, it ran foe a couple hours yesterday, I shut it down and two hours later nothing, didn't do anything with the key, usually a little love tap on the starter will fix this,but it didn't, when I jumped it on the starter it spun but didn't engage, when out this morning and she cranked right up several times. It seems like it does what ever it is doing once it gets hot, but I have no idea

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Solenoids go bad a few ways. One way is the coil that creates the magnetic field to actuate the device becomes weaker at the end of it's life. When the coil cools down they usually become stronger again to some degree resulting in intermittent operation as you described.

tactical45 said:

Anybody have a schematic for this box?

Click to expand...

I found these...

You're going to have to use a voltmeter if you want to solve this without throwing parts at it. Check for +24v on the small wire connecting to the starter solenoid when held in crank (when it won't crank). This will tell you if it is the starter or further upstream such as the switch or PCB. This is easy to solve, but you have to do some quantitative diagnostics to do it economically. Also check all 3 wire connection points on the starter to make sure they are snug and not loose.