Diagnosing CTIS M1078

[RRaulston]

So..... where can you get a CTIS pressure switch for less than $500??? ouch....

 

[coachgeo]

So..... where can you get a CTIS pressure switch for less than $500??? ouch....

if your speaking of the one on the tank.... yeah those are OUCHHH

Find it parts has them same 500.. BUTTT here is some discount codes? https://www.retailmenot.com/view/finditparts.com

found one hundred or so less...... but out of stock so dont trust the price

DANA Spicer Tire Pressure Switch Assembly - 599959 - 599959

DetailsProduct DescriptionDesigned for minimal downtime and fewer maintenance intervals. Engineered, manufactured, and field-tested to ensure the application-specific demands of your vehicle. Trusted by OEMs and fleets. This part is under warranty for twelve (12) Months/1 Year; some exceptions...

www.jittruckparts.com

truck pro is redoing their site to they are down for the night

ebay.... best price so far https://www.ebay.com/itm/3047242975...+3w/AR1DVmT99kWVSTXzaZIkVWRn|tkp:BFBM9JbJgJ5h

Funny thing is ebay ad is from FinditParts....

CTIS Pressure Switch on air tank

TruckPro/Spicer

599959

 

[Ronmar]

So..... where can you get a CTIS pressure switch for less than $500??? ouch....

Thats a tough one. Like the alternators, It is a pretty specific component, and the bandits know it. Thats why I like to throw out cost effective alternatives whenever I can The CTIS sw closes at 117 and doesn’t open again until 89PSI. But there are inexpensive off the shelf 90-120 PSI air compressor switches. I have not found one with normally open contacts though, so these open at 120 and close at 90 to cycle an air compressor this is opposite of the CTIS sw. You could invert that output with a relay, so maybe $20 in parts and a little bit of wiring?

IMO the main purpose of that switch is to allow the air system to recharge fully occasionally. It may be that CTIS also expects to see it open after a certain amount of fill(guessing here)… This behavior could probably be mimicked close enough to keep CTIS happy with a simple programmable interval timer… About $10?

 

[Reworked LMTV]

Thats a tough one. Like the alternators, It is a pretty specific component, and the bandits know it. Thats why I like to throw out cost effective alternatives whenever I can The CTIS sw closes at 117 and doesn’t open again until 89PSI. But there are inexpensive off the shelf 90-120 PSI air compressor switches. I have not found one with normally open contacts though, so these open at 120 and close at 90 to cycle an air compressor this is opposite of the CTIS sw. You could invert that output with a relay, so maybe $20 in parts and a little bit of wiring?

IMO the main purpose of that switch is to allow the air system to recharge fully occasionally. It may be that CTIS also expects to see it open after a certain amount of fill(guessing here)… This behavior could probably be mimicked close enough to keep CTIS happy with a simple programmable interval timer… About $10?

I agree. It would not be hard to do this with a weather-proof box. Speaking of inexpensive work-arounds, like the penny collection I started in the old farm house fuse box. Who needs fuses, when a penny will suffice? Old Abe trick

 

[Ronmar]

I agree. It would not be hard to do this with a weather-proof box. Speaking of inexpensive work-arounds, like the penny collection I started in the old farm house fuse box. Who needs fuses, when a penny will suffice? Old Abe trick

Wouldn't even need a weatherproof box. Cut the connector at the tank and Install the 90-120PSI air compressor sw at the normal location at the tank and install new connections on the end of the wiring harness and weatherproof them to the switch. Splice the relay into the CTIS wiring harness under the trailer and park brake valves in the dash.

The normal CTIS pressure switch config grounds wire 1790/pin T in the CTIS harness when the tank reaches 117 PSI, and maintains that ground until tank pressure drops to 89PSI. So you cut wire 1790, and connect the CTIS controller end to a 24v automotive relay pin 30 and connect pin 87A(normally open contact) to ground. The truck side of wire 1790 you connect to one side of the 24v relay coil, pin 85, and you sample 24v CTIS power from wire 1911/pin H and connect it to feed the other side of the coil at pin 86.

So when you turn on the main switch and start the truck, if the new tank sw is below 90PSI(switch closed), the relay energizes, removing the ground to CTIS. once the air charges to over 120PSI, the new switch opens, de-energizing the relay. This applies that ground to CTIS and it then goes to work like normal… about $25 in common off the shelf parts…

The expensive and hard to find 205F normally closed temp switch(opens at 205) that controls the engine fan, can be replaced in the same fashion using a far more common and affordable normally open automotive cooling fan control sw and a relay…

in playing with my manual CTIS, I know that the PCU can drain the wet tank from full to the 85 PSI protection valve limit in as little as 3 seconds when filling low tires. At a high idle it can take 12-15 seconds or so to refill that tank. I am not sure exactly how the controller interprets/uses that switch info as I have only ever played with working units briefly. It may use the high pressure point to trigger the start of an operation, like it does the initial pressure check to insure the brake system gets topped off regularly. It may use the high and low points like an air compressor control switch to fill in pulses, which would also guarantee a brake tank pressure recharge. But because that sw also cycles due to brake usage, I am sure the CTIS controller ignores it unless it is doing some programmed operation. An interval timer wired in to provide that ground on wire 1790, set to copy a typical high low tank pressure time cycle, say when filling the tires(3-5 sec on - 15 sec off) would allow CTIS to function and also modify CTIS function to allow the tanks to recharge regularly. This might slow down a fill cycle though, particularly if CTIS is filling based on high/low tank pressure sw conditions…

 

[Lostchain]

I am not sure exactly how the controller interprets/uses that switch info as I have only ever played with working units briefly.

Any time that pressure switch is open, the CTIS system will not do anything that consumes air. So for example if you start up with empty tanks, the CTIS system will not even pressurize the wheel valves to check the tire pressure until that switch closes. If it is in an inflate cycle, it will pause the instant that switch goes open. That switch state is continuously monitored. Its been a little bit since I have played with it, but I believe it will continue an already started deflate cycle if the switch goes open during, but as soon as it tries to do a periodic check in of the pressure, it will go back to waiting again until the switch closes, at which point it checks and resumes deflating. Of course for that same reason it will not start new deflate cycle, because it doesn't want to use air for the check.

 

[Ronmar]

Any time that pressure switch is open, the CTIS system will not do anything that consumes air. So for example if you start up with empty tanks, the CTIS system will not even pressurize the wheel valves to check the tire pressure until that switch closes. If it is in an inflate cycle, it will pause the instant that switch goes open. That switch state is continuously monitored. Its been a little bit since I have played with it, but I believe it will continue an already started deflate cycle if the switch goes open during, but as soon as it tries to do a periodic check in of the pressure, it will go back to waiting again until the switch closes, at which point it checks and resumes deflating. Of course for that same reason it will not start new deflate cycle, because it doesn't want to use air for the check.

I suspected as much, and that makes perfect sense, but have no observation to support it

 

[RRaulston]

The pressure control unit is the manifold that the controller manipulates to control the system. It is located under the passenger dash, an aluminum block with hoses connected to it and a black plastic cover on the bottom. It has 3 solenoid valves under that plastic cover. One is the control solenoid, it is normally open to vent the manifold and the controller must energize it to close it and seal the system. It vents the manifold into that plastic cover which has a hose that connects it to a port on the floor to vent the air outside the cab.
The second valve is the supply valve. When the controller energizes it, it lets in supply air from the wet tank to pressurize the system/inflate the tires.
The third valve is the deflate valve. When energized it connects the manifold to a little 6.5PSI pressure relief valve on the side of the manifold block. This vents the system down to that point, which is just enough to keep the wheel valves open. Since the pressure in the tires is greater, air trys to flow back from the tires to the manifold. This reversal in flow causes the dump valves(remote pressure regulators) to vent the tire air rapidly.

The stable pressure it is looking for is the combined tire and system pressure. When the system is sealed and the wheel valves are open the tires should all equalize at the same pressure. If one or two tires are at a different pressure this can take a while to equalize thru the plumbing and the controller may fault Because the pressure is changing.

The only place to really sample the manifold pressure, already has the pressure transducer installed there. You can monitor the pressure at the tire Schrader valves... if you can get it to fill then it was probably faulting because not all the tire pressures were the same initially and it takes a while to equalize them. If low, 30 minutes to fill at idle sounds about right, they take a huge ammount of air. When low, the tires will empty a 120 PSI wet tank down to its 85psi cutoff in 3 seconds...

Finding leaks is a problem on the system as it only pressurizes in pulses and the engine is running. The easiest way is to disconnect the controller connector and jumper 28v to the control solenoid and momentarily jumper 28v to the supply solenoid to pressurize the system(as long as the wet tank is full). the system should then set at tire pressure as long as the control solenoid remains energized and you can look for leaks without the engine running...

my controller was bricked when I got my truck and I decided to go to manual control. Here is a video of how the PCU operates with me controlling the solenoids manually. The gauge on mine is connected where the pressure transducer was connected on the PCU...

So each button is wired into the big cannon plug giving you manual control of the 3 valves? I'm guessing all 3 buttons have a common 24v power wire going to them and each button then has a different valve wire. Hit the button and send power to the respective solenoid?

 

[Ronmar]

So each button is wired into the big cannon plug giving you manual control of the 3 valves? I'm guessing all 3 buttons have a common 24v power wire going to them and each button then has a different valve wire. Hit the button and send power to the respective solenoid?

That would be correct. You close the control then open the supply or deflate solenoids appropriately to control tire pressure.

That was my prototype. I put up a slide show of that original wiring(drawing and pics) In another youtube video On my channel.

I do it a little differently with a latching relay Now. I am working on a updated drawing that I will publish when I get to it

Here is my current system built into the dash…

 

[RRaulston]

That would be correct. You close the control then open the supply or deflate solenoids appropriately to control tire pressure.

That was my prototype. I put up a slide show of that original wiring(drawing and pics) In another youtube video On my channel.

I do it a little differently with a latching relay Now. I am working on a updated drawing that I will publish when I get to it

Here is my current system built into the dash…

OK I watched this one too. I thought I had watched all your videos but missed this one. This is a cleaner setup.....Awaiting schematics!!