Ctis on a m35a3

[Jeffval]

I just put new tires on my M35a3. The CTIS system was working fine. I aired up all the tires to 60 psi. I drove 6 miles and checked the air pressure in each tire. 5 of the tires, are reading 32 psi, but the front left tire is reading 60 psi. The CTIS is running its cycle but is not brining the tires up to 45 psi and the air pressure in the front left tire remains a constant 45 psi. And the CTIS control box will not shut off when I hit the off button. Does anybody have any idea what I should do? Thank you.

 

[HDN]

I'd start with the CTIS troubleshooting instructions in the TMs if you haven't already. TM 9-2320-386-24-1-1 has the unit-level troubleshooting instructions for the CTIS.

 

[glcaines]

I'd start with the CTIS troubleshooting instructions in the TMs if you haven't already. TM 9-2320-386-24-1-1 has the unit-level troubleshooting instructions for the CTIS.

As HDN says, start with the TM. The CTIS on the A3 is a very simple system. Since 5 of the tires are at the same pressure, to me it sounds like you need to remove and clean the wheel valve on the 6th wheel. They are very simple to open up and clean.

 

[Jeffval]

I just put new tires on my M35a3. The CTIS system was working fine. I aired up all the tires to 60 psi. I drove 6 miles and checked the air pressure in each tire. 5 of the tires, are reading 32 psi, but the front left tire is reading 60 psi. The CTIS is running its cycle but is not brining the tires up to 45 psi and the air pressure in the front left tire remains a constant 45 psi. And the CTIS control box will not shut off when I hit the off button. Does anybody have any idea what I should do? Thank you.

 

[Jeffval]

I'll try cleaning the ctis valve. Good idea. I thought that I might have not got the run flat lined up with the valve stem when I replaced the tires. However my CTIS control unit won't shut off when I hit the off button and it won't air up my tires beyond 32 psi. I'd like to bring it up to 45 psi but it won't. I've been looking on ebay for a new ctis controller and some of them have additional letters on the part number. For example my controllers part number is 10114063. The ones on ebay are 10114063 B and 10114063 REV A. Are these upgraded versions of mine or are the for a different vehicle? Thank you J.V.

 

[HDN]

Last I checked, replacement controllers for the truck are pretty expensive. Also, I'm unsure as to how much of the controller's functions are in the box itself rather than the power manifold under the truck - for example, is the Off button turning off the box, power manifold, or both?. I'd either try to take the controller apart to test the button's function, or rig up a separate off switch in the controller's wiring harness to turn the thing on or off.

 

[glcaines]

I think CM Automotive Systems is now out of business. It's too bad, because I've talked to them on the phone in the past and they were very helpful. They even sent me a brand new wheel valve at no cost when I told them it was for my ex-military M35A3. Try cleaning the wheel valve first and see what happens. One thing you might not be aware of regarding the M335A3 CTIS. You should never turn on the CTIS when the weather is cold, or even chilly. Drive the tuck for several miles first, longer if the weather is really cold, to warm up the seals. If the temperature is in the 20s or lower, don't use the CTIS at all. Otherwise, the seals will fail due to being brittle. CM Automotive told me that when I talked to them on the phone. I mention this because we are heading into winter and you live in a cold state.

 

[Jeffval]

I think CM Automotive Systems is now out of business. It's too bad, because I've talked to them on the phone in the past and they were very helpful. They even sent me a brand new wheel valve at no cost when I told them it was for my ex-military M35A3. Try cleaning the wheel valve first and see what happens. One thing you might not be aware of regarding the M335A3 CTIS. You should never turn on the CTIS when the weather is cold, or even chilly. Drive the tuck for several miles first, longer if the weather is really cold, to warm up the seals. If the temperature is in the 20s or lower, don't use the CTIS at all. Otherwise, the seals will fail due to being brittle. CM Automotive told me that when I talked to them on the phone. I mention this because we are heading into winter and you live in a cold state.

Thank you so much for your reply. Cold weather/-40 degrees may have caused the problem with the CTIS system. Last winter, I started the truck to air up one of the tires that went flat. The CTIS control module started behaving differently after then. It won't shut off and won't bring all the tires up to 45 psi. The I aired up all the tires to 50 psi. Hit the highway button and the system released all the air to 32 psi per tire except the left front tire still has 50 psi. I'm going to try cleaning the ctis valve on the left front tire and see what happens. Someone else said the wiring harness could cause the control module to not operate correctly so I'm going to check the contacts. I'll let you know what happens.

 

[87cr250r]

I see so much complaint about the CTIS systems. Is it typically the controllers that fail or the valves and seals? If it's the valves and seals what are you using as a lubricant?

 

[HDN]

I see so much complaint about the CTIS systems. Is it typically the controllers that fail or the valves and seals? If it's the valves and seals what are you using as a lubricant?

I think it's a combination of valve and seal failures. If any gear oil gets into the valves through leaking axle seals, the valves get gummed-up and won't work right. Air seals at the bearings can fail - the M44A3 has four seals per hub whereas I believe the M939A2 has... two? But the 939A2 axles were designed for CTIS from the start while M45 axles weren't.

From what I've seen with the A3 trucks, other culprits include poor quality brass fittings in the wheel CTIS plumbing, which crack and leak, and wheel turret valve seal nuts that weren't torqued to spec.

 

[glcaines]

One other thing to remember is that these trucks range from 25 - 30 years old and most have had minimal or no PM on the CTIS system either during active military use or subsequently. In addition, the M35A3 trucks were the first deuces to have CTIS so mechanics and drivers had no practical experience on maintenance and proper use under different conditions. As HDN mentioned, only a little oil leaking into the CTIS wheel cylinders can end up causing problems and there is no such thing as a seal that is 100% perfect. When I got my M35A3 one of the first things I did was remove all six wheel-valves and cleaned them internally. I also broke down the wheels and replaced the grommet on the valve stems and torqued them properly as well as replacing the O-rings. Virtually no problems with the CTIS since, although I don't often use it because I run my tires at 60 PSI and my tires don't leak air.

 

[Jeffval]

When I replaced the tires, I also replaced all the old seals with new seals and I greased all of the bearings. I did replace some of the plumbing fittings. Instead of the cork, I used gasket sealer in the green tube to fill the little cavity. However prior to this maintenance I did see differential fluid on the outside of two tires and when I took the tires off the rims there was about a cup of differential fluid inside each tire and the brake pads were covered with differential fluid. So I'm guessing a differential fluid clog is the culprit in my left front valve. I'll have more time to work on it today.

 

[87cr250r]

I ask because I used to have a lot of pneumatic controls in my fleet. Many valves would fail every 2-5 years. The crews were using whatever white grease they had which was usually white lithium. They were supposed to be using silicone on PTFE grease. The petroleum greases caused premature determination of the rubber. With PTFE greases such as Krytox GPL205 these controls can easily exceed 20 years without service.

 

[Jeffval]

I ask because I used to have a lot of pneumatic controls in my fleet. Many valves would fail every 2-5 years. The crews were using whatever white grease they had which was usually white lithium. They were supposed to be using silicone on PTFE grease. The petroleum greases caused premature determination of the rubber. With PTFE greases such as Krytox GPL205 these controls can easily exceed 20 years without service.

That's good to know about the Krytox GPL205 grease. The next time I grease everything I'll use it! Thank you

 

[87cr250r]

The price tag is a bit of a shocker. It's $200 for an 8oz tube but that is a lifetime supply for normal people. I started buying a tube for every propeller shaft seal job which is close to $20k. It takes just over 4oz which means I can't use a tube twice

 

[Jeffval]

The price tag is a bit of a shocker. It's $200 for an 8oz tube but that is a lifetime supply for normal people. I started buying a tube for every propeller shaft seal job which is close to $20k. It takes just over 4oz which means I can't use a tube twice

I took the rim off of the tire and found that the run flat wasn't lined up with the valve stem. I knocked it into place with a dull chisel and hammer, cleaned the Ctis apparatus of oil, and hooked everything back up. While the tire was still jacked off the ground, I started the truck and set the tire pressure to highway 45mph. The one tire that i just fixed, aired up to a total of 22 psi. Meanwhile the other tires dropped from 32 to 22 psi. I checked everything, including cleaning contacts, using dielectric grease when reconnecting. The main controller is continuously blinking "highway" and won't shut off. It will dump the air if I tap the lowest setting, but I don't want to manually pump them up again. I guess I'll have to buy a replacement control module. There's several models that all look identical online that have the same part # as mine 10114063, but they have additional letters like "B" and "Rev A". I'm wondering if they are upgraded models, from a different vendor or for different vehicles?

 

[glcaines]

It's good that you at least now have all six wheels airing up to the same level. You are making progress, so don't get discouraged. Are you certain that you don't have an air leak in the system somewhere such that the compressor can't keep up with the leak and the controller is trying desperately to air up the tires to 45 PSI, but can't get past 32 due to a leak? What happens if you set the controller to 32 PSI or somewhat lower? Will the controller then shut the CTIS off?

 

[Jeffval]

It's good that you at least now have all six wheels airing up to the same level. You are making progress, so don't get discouraged. Are you certain that you don't have an air leak in the system somewhere such that the compressor can't keep up with the leak and the controller is trying desperately to air up the tires to 45 PSI, but can't get past 32 due to a leak? What happens if you set the controller to 32 PSI or somewhat lower? Will the controller then shut the CTIS off?

Hi. I thought their may be a leak but I didn't hear anything. I used the liquid leak detector on all the fittings I could find. However just prior to the system discharging it's extra air, I do hear a hissing noise. I don't know if that sound is a leak or just the air going through the system. There's a bunch of hoses in a tight space behind the fuel tank and it's difficult to locate a leak. As for the control module I think it got ruined when I changed out the batteries. I accidentally touch the opposite terminal with the wrench and it created a spark. Afterwards the CTIS control module started acting irradically, the air pressure buzzer stopped buzzing and the hazard light switch won't pull out. I don't know how these malfunctions occurred because the accessory switch was in the off position at the time the battery sparked?

 

[glcaines]

The hazard light switch is the turn signal switch, there is nothing to pull out. You simply move the arm up past the right turn position and the hazard lights come on. The cab hazard light is the same light as the light on the turn signal switch. It is very common that this light doesn't work properly because of a faulty ground to the steering wheel column. The only thing that ground is used for is the light that flashes. Even if this bulb doesn't light, your turn signals and hazard lights will still work. If the bulb is good and is not lighting up when it should, scrape some paint off of the column and make sure you are getting a good ground contact between the switch and the column.
Shorting between ground and a battery and sparking shouldn't have impacted anything. However, when working around the batteries, always disconnect the negative lead to ground from the battery post. I know someone that accidentally shorted the battery positive to ground. The wrench welded itself in place and the battery exploded, blowing sulfuric acid all over him and his face.

 

[Jeffval]

The hazard light switch is the turn signal switch, there is nothing to pull out. You simply move the arm up past the right turn position and the hazard lights come on. The cab hazard light is the same light as the light on the turn signal switch. It is very common that this light doesn't work properly because of a faulty ground to the steering wheel column. The only thing that ground is used for is the light that flashes. Even if this bulb doesn't light, your turn signals and hazard lights will still work. If the bulb is good and is not lighting up when it should, scrape some paint off of the column and make sure you are getting a good ground contact between the switch and the column.
Shorting between ground and a battery and sparking shouldn't have impacted anything. However, when working around the batteries, always disconnect the negative lead to ground from the battery post. I know someone that accidentally shorted the battery positive to ground. The wrench welded itself in place and the battery exploded, blowing sulfuric acid all over him and his face.

That's good insight. Thank you. One more question...When I disconnected the ctis cm there's 2 ground wires that screw into the back side of the terminal. One ground comes from somewhere in the truck. The other ground wire is about 6 inches long and is just independent/ by itself. I forgot the configuration when I went to put it back together. Does the independent wire attach to the same terminal on the back side of the cm as the ground wire coming from the truck?