A little ctis advice while recovering please!

[Slate]

I am in New Mexico and recently picked up a 923A2. My front drivers boot is leaking oil now and my all ctis lights blink. The air compressor is constantly running. Can I unplug the ctis and drive home? Or just deal with it? I'll m a deuce guy and don't really know the ctis system. I am currently taking a break but have another 400 mes to go. Thanks

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[10isBestmm]

Im no expert so corect me if i have it wrong, but the ctis wont go active until the governor air pressure cutoff. Fixing the air leak might fix it. Madams showed me this on my 7 ton.

 

[Slate]

It started out fine. IM hearing an air leak under front of engine. It's slowly getting worse the more I drive these horrible New Mexico roads.

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[10isBestmm]

If its getting worse then you might not go anywhere if the air brakes all lock up from being under the psi requirement.

 

[Slate]

Primary air pressure is just below 90 secondary is perfect.

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[Slate]

Could the air dryer cause the system to continually cycle and purge?

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[Jbulach]

Just unplug the cannon plug on the back of the ctis controller , that will eliminate it from the equation, but if all five lights are flashing it’s not causing your air pressure problem.

 

[Slate]

Just unplug the cannon plug on the ctis, that will eliminate it from the equation, but if all five lights are flashing it’s not causing your air pressure problem.

I got that after reading a bit. Unplugged and back worked for 60 miles then blinky again. Dryer is purging every 10 min or so and primary is losing air fast enough I can see needle move. I'm getting down the road though.

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[Coffey1]

Yes unplug the cannon off controller
Check air pressure in all tires and air them up to prober pressure.

That will take ctis out of the loop.

 

[Slate]

Tires are good but dryer is piping off every few seconds now.

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[simp5782]

Tires are good but dryer is piping off every few seconds now.

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Find the leak. The air dryer only sees air from the wet tank. It doesn't see what the gauges display. You have a leak on the primary side or you have a leaking check valve causing a back flow.

Shut your primary air tank valve. Located on the front of the wet tank. Your system will still operate normally with the valve closed. The secondary tank will take over the spring tank fill duties rather than sharing them

If the air dryer continues to purge with the primary tank closed then you have a leak on the pressure protection side and a bad primary check valve

 

[Slate]

Which is primary second and wet? New to 923.

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[simp5782]

Which is primary second and wet? New to 923.

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Wet is under the truck. Right in front of the transfer case. Primary is top passenger tank. Secondary is bottom. Spring brake is on the drivers side behind step

Primary air lines are red. Secondary are green. Pressure protection is yellow. Vent is white.

 

[simp5782]

If its getting worse then you might not go anywhere if the air brakes all lock up from being under the psi requirement.

M939s are not designed like normal trucks. If the secondary is holding air it will fill the spring brake tank and take over those duties. They both send air to a valve that allows air from either tank to supply depending on which has the most pressure

 

[Slate]

Bad primary check valve. Would that be the little governor needs replacing?

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[simp5782]

Bad primary check valve. Would that be the little governor needs replacing?

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No. Its on the front of the tank itself between the fender and tank. Napa Kn23000

So the primary tank holds air once you close that valve? Compressor still cycling? If so it could be a bad governor. You can crack the drain valve on the wet tank so you can drive and the air dryer won't continue to purge all the time but this will allow water to escape and drive on

 

[Slate]

There is a red going in top tank and a green from top tank to wet tank.

 

[Slate]

So with top tank shut it doesn't just cycle all the time.

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[simp5782]

Then you have a primary side leak. That is easier to track down if the primary loses pressure on the gauge but the secondary holds that makes it even easier since that means its not on the spring tank side

 

[simp5782]

Just drive it on home with that valve closed. That is what they are for.