CTIS: How I fixed my 5 flashing lights

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Truck Girl

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I've been pouring over these forums a great deal lately searching for answers to the delights of CTIS, and feel like I should share a little bit of information that really helped me. For my particular case of the 5 lights issue it turned out to be the pneumatic controller had lost one of the three solenoids. You can find out if this is the case with a quick resistance check on the terminals. A-E, A-F, and B-D all should have conductivity. My two working ones were around 40-50 ohms. The third was an open circuit. As these controllers are way out of my budget I went looking for repair parts.

Google image search is amazing for this sort of thing, and I ended up finding this little gem:

Peter Paul Electronics 24 vdc solenoid part# 5C-13-K24-PPF

The same vendor has it up on Amazon, Ebay, and a few other sites. Only three left though, but perhaps the part number which differs from the original can be of some use. It was an identical form factor, the only difference being it has about 70 ohm resistance. It has yet to give any signs of trouble, and my CTIS controller is worlds happier.

Edit: Truck is a 1991 M923A2
 
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gottaluvit

New member
Kind of an old thread but actually the best one I found describing this that a google search brought up. I have a full air blow by coming out of the threaded vent on the PCU, and these solenoids were my first suspects. All five lights flashing. Tore the PCU completely apart to make sure no o-rings were blown and they all look good. Being that the thread has only post, and it was the poster's only post, I was wondering if anyone else has verified that testing the solenoids with these terminals is correct? Also, which solenoids (S,D, or C) are on which terminals? I just didn't want to damage any more solenoid wires than necessary if at all possible. My A-E and A-F terminals test about 48+- but zero ohms across the B-D terminals.

Thanks in advance, Jim
 

gottaluvit

New member
Thanks Andyrv6av8r. I already ordered a used pcu off ebay figuring at least two of the solenoids should be good. At least with it I can cut into the insulation and figure out terminal label letters to which solenoids and cheaply eliminate questions pertaining to consistency of test outcomes.

Coffey 1, mechanically my pcu is in pristine condition. If the solenoids are all good, what could cause the constant blow by with five flashing lights? Maybe a shorted wire not letting solenoid open or close? Spicer's 2017 manual says to try another known working pcu with five flashing lights. That's just not possible.

When the new-to-me one comes in I should know more and will follow up on this thread to help others. I couldn't find any thing at all about the constant blow by in Spicer's manual or searches which should have brought it up from the TMs if they even spoke on it. I need a hard copy TM on this truck so I can look at it as I work on the truck instead of going back in the house to look on the computer. Can't see phone screen outside. Pics will follow as well. Thanks guys.
 

gottaluvit

New member
Got my new-to-me pcu in and at least one of the three solenoids were good. I knew it was a gamble getting the untested unit for as low a price as I did. Changed it out and system works like before. It aired up a low tire pressing the runflat and it kicked back to highway on it's own and topped them all off and has a steady glowing highway light now. So the solenoids can and do go bad on their own. It worked when I parked it last fall and didn't when I started up the truck in February. All good now. Here is a link to a great thread on the subject. My control solenoid was bad.
https://www.steelsoldiers.com/showthread.php?137569-M939A2-CTIS-PCU-solenoid-replacement
 

Western PA M923A2

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Good afternoon all! Sorry to rehash an old topic, but here we go. I've owned my 1991 M923A2 for 3 years now and the CTIS never seemed to work, so I disconnected the wiring harness at the control unit. After doing a few parades and other get togethers with other guys in my area with MV's, I've got the itch to get the CTIS functional. I don't have the all 5 lights flashing simultaneously... whatever button I press, that's the only one that flashes, and it just stays flashing and I never heard the sound of air flowing as I've heard that the CTIS makes when it's active.

Any thoughts, or better yet, a remedy? Thanks in advance!!
 

cbrTodd

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Good afternoon all! Sorry to rehash an old topic, but here we go. I've owned my 1991 M923A2 for 3 years now and the CTIS never seemed to work, so I disconnected the wiring harness at the control unit. After doing a few parades and other get togethers with other guys in my area with MV's, I've got the itch to get the CTIS functional. I don't have the all 5 lights flashing simultaneously... whatever button I press, that's the only one that flashes, and it just stays flashing and I never heard the sound of air flowing as I've heard that the CTIS makes when it's active.
Any thoughts, or better yet, a remedy? Thanks in advance!!
The single flashing light means it has never closed the CTIS specific 120 psi pressure switch at the tank saying that it has enough pressure to attempt to function. Seems like multiple people have found that the sensor needs more than 120 psi to read 120 psi when it gets some age on it. You can try to increase your truck air pressure a little at the air governor and see if that will make it close. It worked for me. If that doesn't work, you can jumper the switch to see if it is just dead or drifted way off. If the switch needs replaced, they have been available on Ebay in the past. The part number is in one of the CTIS threads here, can try to look later if needed.
 

Western PA M923A2

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West Newton, PA
The single flashing light means it has never closed the CTIS specific 120 psi pressure switch at the tank saying that it has enough pressure to attempt to function. Seems like multiple people have found that the sensor needs more than 120 psi to read 120 psi when it gets some age on it. You can try to increase your truck air pressure a little at the air governor and see if that will make it close. It worked for me. If that doesn't work, you can jumper the switch to see if it is just dead or drifted way off. If the switch needs replaced, they have been available on Ebay in the past. The part number is in one of the CTIS threads here, can try to look later if needed.
Hello Todd, and thanks for the reply and the info! So tell me... where on my truck would I find the 120 psi pressure switch that you mentioned?
 

mzak88

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Grand Forks, BC, Canada
I’ve acquired a 1990 M925a2 three months ago. The CTIS controller was unplugged when I got it. The importer told me the CTIS was deactivated. Everything appears to be intact on the truck. I plugged in the CTIS controller and I will have a single flashing light at whatever function I select, the after 10 minutes of driving it’s 5 flashing lights. The “overspeed” light does come on at 55 and at a lower speed when “sand” is selected. I have no audible noise in cab or anywhere when I make selections. I am dying to try to get mine going. Any opinions?
 

Andyrv6av8r

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With no audible noises, pressure checks, I would start with the PCU. Ohm out the coils and verify that they are all good. If so, take it apart and clean up all of the 3 valves. It could even be that you aren't getting pressure to the PCU because of a bad pressure switch on your wet tank.
 

mzak88

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Got it working! I turned the governor up a bit and I got all kinds of noises happening now. Inflated all tires evenly to 70 psi. Forgive me, I’m a newb. Now I would like to figure out how to upgrade to the 90psi Hwy setting.
 

Jbulach

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Sunman Indiana
Got it working! I turned the governor up a bit and I got all kinds of noises happening now. Inflated all tires evenly to 70 psi. Forgive me, I’m a newb. Now I would like to figure out how to upgrade to the 90psi Hwy setting.
What pressure did you have to turn the governor up to?

If your inflating to 70psi you should already have the updated ECM, now all you need is the 90psi wrecker transducer, and maybe the wheel valve upgrade depending on how they act. All of my old style wheel valves hold all the way up to 100psi, except one, but I think the issue with that one is a restriction in the hub that I haven’t chased down yet. I think I have a few extra NOS 90PSI transducers around here somewhere that I would let go cheap.
 
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mzak88

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Grand Forks, BC, Canada
I backed the governor screw out 1/2 turn so it now builds to 123ish. My system works good on HWY setting however if I try sand or cross country the run flat light comes on incessantly. I tried sand yesterday, fronts did not go below 60, pass side mid axle tire nearly went flat other tire 25. Rear axle was 50. I also had the 4 light flash going on. Would like to get this all figured out but thrilled I have some function happening. Would I need to change anything else besides the transducer? I had a guy on eBay tell me I would need the updated controller, wheel valves and pcu. I would certainly be interested in taking one of those off your hands. :)
 
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Rooster828

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So I got the 5 flashing lights and it started deflating my tires . So I unplugged the box , replugged it in with no change. Then I tried the trick where you hold the run flat and emergency button to equal the pressure out in all tires which from what I understand is also like a master reset for the control box. Well this worked as far as the flashing lights , but now it flashes on hwy mode like it should and it sounds to be inflating the tires but instead it’s still deflating the tires . I had manually filled them to 30-40 psi and once the truck was running it deflated the tires all down to 20 psi then a couple min later it’s down to 15.
Thinking it may be time just to cap the hubs off and be done. Just sucks that my tires slowly loose air and it takes forever to fill them with my 30 gal compressor
 

Afterburn

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Thanks Andyrv6av8r. I already ordered a used pcu off ebay figuring at least two of the solenoids should be good. At least with it I can cut into the insulation and figure out terminal label letters to which solenoids and cheaply eliminate questions pertaining to consistency of test outcomes.

Coffey 1, mechanically my pcu is in pristine condition. If the solenoids are all good, what could cause the constant blow by with five flashing lights? Maybe a shorted wire not letting solenoid open or close? Spicer's 2017 manual says to try another known working pcu with five flashing lights. That's just not possible.

When the new-to-me one comes in I should know more and will follow up on this thread to help others. I couldn't find any thing at all about the constant blow by in Spicer's manual or searches which should have brought it up from the TMs if they even spoke on it. I need a hard copy TM on this truck so I can look at it as I work on the truck instead of going back in the house to look on the computer. Can't see phone screen outside. Pics will follow as well. Thanks guys.
I realize this is an old post, and not sure if anyone told you before. Individual pages from digital TM's can be printed, I do it all the time.
 
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