Help needed/truck stuck - Cycling pneumatic relay under PDP in 2000 M1088 w/3126

[ckouba]

Need some help from the forum's collective knowledge....

Took my truck ~100 miles yesterday to Eugene to have the habitat structure blasted and painted. Drive down was hot with a bit of traffic but went smoothly. The fan cycled a bit more than expected but ran everything ran fine despite my nervousness. No reasons to think anything was going to go wrong.

Got to the shop and took about an hour and a half to unload the camper. Went to move it out of the building and park it and everything started fine, but after ~10 seconds, what I presume to be a relay started to endlessly cycle. I presume it's pneumatic because by the time we had driven across their lots to park the truck, the low air alarm had started whining.

The relay sounds like it's located below the PDP behind the kick panel but I didn't have time to troubleshoot because we were already past closing time, the shop was closing up, and I needed to get out of there. I was also out of daylight.

I am back home, ~100 miles away, and need to head back and get it running. I will start poking through TM's but if anyone has a strong idea of what is happening and how to resolve, please drop a note here.

Thanks!!

 

[Skyhawk13205]

Need some help from the forum's collective knowledge....

Took my truck ~100 miles yesterday to Eugene to have the habitat structure blasted and painted. Drive down was hot with a bit of traffic but went smoothly. The fan cycled a bit more than expected but ran everything ran fine despite my nervousness. No reasons to think anything was going to go wrong.

Got to the shop and took about an hour and a half to unload the camper. Went to move it out of the building and park it and everything started fine, but after ~10 seconds, what I presume to be a relay started to endlessly cycle. I presume it's pneumatic because by the time we had driven across their lots to park the truck, the low air alarm had started whining.

The relay sounds like it's located below the PDP behind the kick panel but I didn't have time to troubleshoot because we were already past closing time, the shop was closing up, and I needed to get out of there. I was also out of daylight.

I am back home, ~100 miles away, and need to head back and get it running. I will start poking through TM's but if anyone has a strong idea of what is happening and how to resolve, please drop a note here.

Thanks!!

Sounds like your fan solenoid. Good luck

Checking the FMTV fan system

Here are some notes on the engine cooling, fan system components. The temperature switch is located on the coolant piping in front of the engine. This is a switch, not a sensor, and has two wires. It is a Kysor 07950, 200 deg, NC-normally closed when cold (reads zero resistance), two wire...

www.steelsoldiers.com

 

[ckouba]

Should also say that someone went out and tried the ignition this morning and the solenoid is still clicking after everything cooling down overnight.

 

[NDT]

Fan solenoid and CTIS control live there. I would guess CTIS as the fan doesn’t consume air.

 

[Ronmar]

Unplug your CTIS controller and see if that stops it. You can also turn on the fan fording sw to see if that stops it. If it is cycling regularly it is probably the CTIS…

If CTIS STOPS IT, just leave it unplugged and check your tire pressures and drive home. If the fan sw stops it remove I believe CB 22 which should keep the fan engaged for the drive home….

 

[ckouba]

Thanks gents. Packing up now to head down to troubleshoot.

 

[ckouba]

On site.

Turned on ignition. Still cycling, 2x/sec or so.

Unplugged CTIS controller, all good.

Does that mean my controller just took a dump?

 

[ckouba]

Starting to scour TM's but if anyone can point me to the correct one, I would appreciate it.

 

[Ronmar]

Starting to scour TM's but if anyone can point me to the correct one, I would appreciate it.

Could be, also could be a bad ground power or pressure sensor or wet tank sw. what are the indicator lights doing?

 

[NDT]

Starting to scour TM's but if anyone can point me to the correct one, I would appreciate it.

The big one. I suspect it’s the valve module not the controller.

 

[ckouba]

Ronmar - I didn't note this when I was down there but it was in HWY mode and I think the indicator was flashing (just that one). Maybe the HWY and RUN FLAT. I am forgetting now. It was doing something though, not just all dark.

With the truck functional enough to get home, I called it a day and drove back to Portland. I will bring a hose and air chuck with me when I pick it up and make sure tire pressures are good and then drive it home.

I've been poking around and have found something for CTIS troubleshooting: TM 9-2320-365-20-2; section 2-24, page 2-1767

Step 6 tells me to "Repair or replace manifold valve assembly (para 12-7)", so now trying to find that...

Thanks for the pointers this morning!! Glad it will still get itself home.

 

[NDT]

"Find" as in a new one or on the truck? You know, could there be a possibility that they poked a hole in a tire? The system is supposed to keep the tires at pressure and overcome small leaks.

 

[ckouba]

Not quite sure what your question is NDT. I will look at the CTIS component behind the pass kick plate to see if there is something mechanical wrong with it. Someone on the FB group suggested that, along with a servicing of the dryer.

 

[ckouba]

"Find" as in a new one or on the truck? You know, could there be a possibility that they poked a hole in a tire? The system is supposed to keep the tires at pressure and overcome small leaks.

Forgot to mention the tires were all holding air. They were still robustly inflated when I got back down there today.

 

[coachgeo]

could a short be making the solenoid click on and off..... like somewhere a hot wire is shorting onto a wire that activates the solenoid?

 

[ckouba]

FYI - Thanks for the help, got the truck home today with the unplugged CTIS. Will take a look at the manual conversion set up before diving through the troubleshooting process.