CTIS Question

[j_boucher]

As you all know I picked up my M1078 last week and have been going through all the systems and I noticed something on my CTIS control box and I cannot find anything in the troubleshooting guides and such.

When I press the I switch the ignition rocker switch I see the lights on the CTIS all light up and then a solid highway, however if I switch it to another mode it does nothing except for the light illuminates for that mode but the system doesn't do anything, All I could find in the troubleshooting were if 2 lights were solid or lights flashing .

All tires have and hold air

Any insight is appreciated

 

[Ronmar]

Have you reached 125PSI in the wet tank(brake service tanks)? CTIS will do nothing until it see enough pressure in the wet tank to close the pressure switch at the wet tank.

 

[j_boucher]

Have you reached 125PSI in the wet tank(brake service tanks)? CTIS will do nothing until it see enough pressure in the wet tank to close the pressure switch at the wet tank.

I would assume so but not sure the brakes are at 120 PSI , Ive sprayed soapy water everywhere on the wet tank connections and around various fittings on the vehicle and no leaks but I did find the tractor protection valve needs a rebuild as it dumps pressure when the brakes are applied but if I don't press the brake I hear no leaks , I know I have some sort of leak though as the tanks will go empty after a few hours

 

[Mullaney]

I would assume so but not sure the brakes are at 120 PSI , Ive sprayed soapy water everywhere on the wet tank connections and around various fittings on the vehicle and no leaks but I did find the tractor protection valve needs a rebuild as it dumps pressure when the brakes are applied but if I don't press the brake I hear no leaks , I know I have some sort of leak though as the tanks will go empty after a few hours

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You said "The brakes are at 120 PSI" and I am guessing by saying that, you mean that the gauges are showing 120psi? If that is so, you need to get more pressure before anything is going to happen with CTIS.

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[j_boucher]

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You said "The brakes are at 120 PSI" and I am guessing by saying that, you mean that the gauges are showing 120psi? If that is so, you need to get more pressure before anything is going to happen with CTIS.

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Thanks for the help, so a question if I need to increase the pressure in the wet tank do I do it at the air compressor or the valve on the tank? I will tackle that after rebuilding the tractor protection valve in the rear

 

[Ronmar]

You adjust the governor on top of the compressor, but you need to connect a gauge to the wet tank to adjust this accurately to 125. Procedure is in the manuals...

The CTIS switch closes at 117, so the pressure may not be getting high enough to close the switch...

 

[GeneralDisorder]

If the pressure is up and the system isn't activating you can just insert a jumper wire between the two pins on the harness connector for the pressure switch at the wet tank and that will fool the controller into beginning it's pressure check/inflate/deflate cycle. Most of the time it's a wet tank pressure problem but the switch can fail or get broken also.

 

[j_boucher]

If the pressure is up and the system isn't activating you can just insert a jumper wire between the two pins on the harness connector for the pressure switch at the wet tank and that will fool the controller into beginning it's pressure check/inflate/deflate cycle. Most of the time it's a wet tank pressure problem but the switch can fail or get broken also.

Thanks ... I ordered an air pressure gauge for the tank, I will test it this weekend

 

[aw113sgte]

On my 2007, the governor was set a little low so I would get intermittent CTIS operation. That would be my first area to check

 

[j_boucher]

So, I attached a pressure gauge it does go to 120-122 but it slowly bleeds off to around 100, and then the compressor kits back in . So I must have a pretty good leak somewhere " I think it is the tractor protection valve " as it bleeds off when I hit the brakes, But at least I have a starting point, waiting on a re-build kit now hopefully it gets here in the next few days. I can't hear or find any leaks anywhere except the tractor protection valve when the engine is off. Headed out with soapy water to check fittings and such when it's running.

 

[flyfishtrailer]

So, I attached a pressure gauge it does go to 120-122 but it slowly bleeds off to around 100, and then the compressor kits back in . So I must have a pretty good leak somewhere " I think it is the tractor protection valve " as it bleeds off when I hit the brakes, But at least I have a starting point, waiting on a re-build kit now hopefully it gets here in the next few days. I can't hear or find any leaks anywhere except the tractor protection valve when the engine is off. Headed out with soapy water to check fittings and such when it's running.

You may also have a leaks (s) at the CTIS axle seals if you have checked all of the lines and valves along the way and had no luck. They seem to be one of the main areas of leaks in these trucks

 

[Ronmar]

Look for air leaking away out the vent up in front of the radiator. That would indicate the treadle valve or park valve is leaking Draining away the system air…

 

[j_boucher]

You may also have a leaks (s) at the CTIS axle seals if you have checked all of the lines and valves along the way and had no luck. They seem to be one of the main areas of leaks in these trucks

Thanks I guess I will need check the TM's and see what is needed to check those

Look for air leaking away out the vent up in front of the radiator. That would indicate the treadle valve or park valve is leaking Draining away the system air…

Is it located up front near the grill area? Grill is off and being prepped to be painted

as for the truck, I noticed it starts to drop off as soon as the drier releases air. It dropped faster when it was cold than when the truck was warmed up dunno if that is a symptom of anything. I sprayed every fitting and hose I could find and couldn't see any leaks, when the truck was off I couldn't hear anything, then again as an old helicopter crewman it could be blaring and I prob wouldn't hear it.

 

[Ronmar]

With the grill off, thats easy then, peek up in front of the top of the radiator. There is a pass-thru located there. The pedal and the park valve vents are tied together behind the heater and vent thru that port When you let off of the pedal or set the park brakes. If for instance the pedal supply side was leaking, since the pedal is not depressed, it would send that leaking air right to the vent port, same with the park valve in the dash…

 

[j_boucher]

With the grill off, thats easy then, peek up in front of the top of the radiator. There is a pass-thru located there. The pedal and the park valve vents are tied together behind the heater and vent thru that port When you let off of the pedal or set the park brakes. If for instance the pedal supply side was leaking, since the pedal is not depressed, it would send that leaking air right to the vent port, same with the park valve in the dash…

I checked it seems fine... but I did find near the driver's side behind the grill 3 fittings were loose . I don't know if this is how it is supposed to work, but since fixing those leaks the brakes keep their pressure up when the ignition is off, I turned the truck on after an hour the brake gauges still said 120 and no alarm but the wet tank was almost empty.

So I'm curious about another item... how does the dryer know when to dump air? Does the governor control that? Just curious if I had to increase pressure wouldn't the drier dump at the same pressure it's dumping now? When I say dump I mean the quick burst of air it releases. I've Been reading a lot trying to learn these systems better.

Thanks for all the help

 

[GeneralDisorder]

The governor both unloads the compressor (it sends tank air to the unloader pistons on top of the head and these hold the intake disc valves open), and controls the dryer purge at the same time. When wet tank air pressure drops below the governor set-point it vents the air from the unloader pistons. If you haven't serviced your dryer yet you should make that a priority. They can leak down air from the wet tank if the discharge check valve isn't sealing properly.

 

[Ronmar]

When the governor unloads at its set pressure, it sends system pressure to the small port on the bottom of the dryer. That applied pressure opens the purge valve on the bottom of the dryer To exhaust the collected moisture. There is a check valve in the top outlet port to the wet tank To keep air from flowing back from the wet tank. Air leaking out the purge valve all the time would indicate the dryer check valve is leaking.

there is a check valve up in the front bumper below the red gladhand that feeds the wet tank so a towing vehicle can fill the truck air system and the blue glad-hand can operate the truck brakes remotely. Look for air leaking out the front red glad-hand vent.

the protection valve on the back of the wet tank(looks like a regulator) only lets air out of the wet tank if the tank pressure is above 85 PSI. That air feeds the CTIS and fan solenoid on the passenger side behind the grill. If the wet tank leaks to zero the air is probably going out thru either or both of the 2 check valves. If it only drops to ~85, it is leaking thru CTIS or the fan solenoid plumbing…