Manual ctis

[Andrmorr]

My CTIS Dumped my tire pressure while I was driving to the Denton Rallye...Got me thinking that I like the CTIS but am not impressed with the computer control of it. Wondered if a plain regulator valve could be put in place of the computer control...set the regulator for 70psi...check the gauge every so often...done. Any thoughts about if it will work or not? Better ideas? A valve core in each tire stem is the last line, but I'm sure it's possible to utilize the CTIS and make it more dependable.

 

[MtnSnow]

I found before pulling my CTIS off that it was usually one of the wheel valves or a QRV that was the root of my issues. I pulled mine as it's not often enough that I need to deflate/inflate to keep fixing the CTIS. Theoretically using a regulator should work but you will also need to have two quarter turn shutoffs one on each side of the regulator and the one between the regulator and the wheels will need to be on the open end of a "tee" so pressure can be bled off.

 

[Suprman]

If the system is unintentionally dumping tire pressure then you have a leak somewhere and when the system sends pressure to fill some is escaping and the wheel valves are seeing less pressure than they should. If you made something to send air manually, like a hand valve with a regulator, you would still have the leak and your end result would be the same.

 

[MtnSnow]

Suprman is correct even with a manual control if there is issues downstream from the manual control you will still wind up flat tires and this is why I pulled mine finally and just use an air hose.

 

[Gunzy]

I have "Manual" inflation. It consists of a gladhand with an air hose and a pressure guage with tire chuck. Works flawlessly every time and has "0" failure points. It has and never will let me down. This works best for me but your operation, use, and mileage may vary.

 

[Andrmorr]

If the system is unintentionally dumping tire pressure then you have a leak somewhere and when the system sends pressure to fill some is escaping and the wheel valves are seeing less pressure than they should. If you made something to send air manually, like a hand valve with a regulator, you would still have the leak and your end result would be the same.

I wish it was a leak...they can be fixed...but no leaks...checked with system at pressure, engine off, key switch on, no leaks...after the pressure dump, I aired system back up with gladhand hose (and a sore thumb) and drove home. Computer went to sand mode or something is my guess...just tired of constant issues with CTIS doing what it wants...when it wants...why should it take 40 minutes to air up tires at start up, or 20 to deflate (per manual), what logic is in use if one wheel gets hurt (think bullet hole in combat), you put it in RUNFLAT while trying to get away, and the system takes both tires on that axle to the lower pressure? That's useless...it should send pressure to the wounded tire not deflate it's axle mate...
If I put a regulator with gauge and a bleed for each axle in the cab then pressures could be monitored and changed quickly and with some assurance it's not going to change without my wanting it to. In the event of a cut tire, I send 70psi to all the control lines... if a tire is low it takes air, if a tire is full it equalizes with the control line and continues doing it's job...

Ever notice the CTIS puts pressure on each channel for only two seconds at a time? No wonder it takes so long to air up 6 tires when it's only sending air to each axle pair for two seconds at a time...my thought is to send 70psi to all tires at once and go do something else like packing...can't over pressure since regulator holds at 70psi...close regulator and check line pressure of control lines... when the control lines read a steady 70 psi, then the tires are full...close regulator feed, bleed off the control lines, done. To air down, I'm thinking a 3 way selector and a momentary switch to activate each dump valve or just dump each tire manually since air dumps would be rare... Whether it happens or not this will be just another project to smear some mental grease on...

 

[Jbulach]

Andrmorr, or anyone or any one else ever accomplish this?
Until someone figures out how to reprogram or build a new CTIS modual, I'm looking at this for a solution to run lower air pressure in my rears, than front for a better highway ride on my M925A2 while empty.
I also need more than the 60 PSI that the CTIS is delivering when I have a full load of stone on.
I love the ability to air down when I leave the road, but have resorted to putting valve cores in the rears so I can run 90 PSI to handle the weight.
So... I'm looking for a schematic and types of air valves and regulators to build a manual, pneumatic, two circuit, CTIS, control.
I'm thinking I need two regulators for my desired front and rear tire pressures and could possibly share another single regulator set at 12 PSI with a couple 3 position switches to get the wheel valves to open when airing down, and dump off air when system is idol at desired pressure. Does this sound right?

 

[Andrmorr]

I built a manual system by getting an air manifold log and plug it into the front glad hand, running two main lines (one down each side of the truck) with an air chuck outlet at each tire.
I have a main regulator on the front where it comes off the gladhand and I use clip on airchucks so its a matter of putting an air line on each tire and go make a sandwich while the tires air up or down. The main regulator up front makes sure it can't over pressure and if you needed a different pressure for the rear you could use a 4 hole manifold and run two lines to the fronts and two lines to the rear...it's quick and unless you have a leaking tire it's dependable...

 

[Jbulach]

Ok, thanks.
I'm hoping someone has built one that can be used on the fly through the factory plumbing. I'm sure I'll figure it out but I'm not familiar with what air valves are out there. I will start drawing and searching valve specs, if no one else has anything.
Will post back with details if I make it happen.

 

[74M35A2]

The CTIS controller just controls air valves in sequence, but it is not as easy as just running a regulator line and you're done. As mentioned or partially mentioned, the normal state is no pressure in the fill line when driving, and it actually sends pressure to deflate or fill the tires, and then bleeds that off to zero again when done. This is why it is automated. You could do it with a cab mounted regulator and such, but it would take a fill valve, regulator, and another valve to dump when done, and you would have to remember to do that sequence every time. It would not be that difficult to do though. Is this my next adventure after the bolt on 8.3 serpentine A/C compressor bracket?

 

[Jbulach]

Are you official done trying to reflash the CTIS modules? I was hoping someone could make it work!
I think the manual setup will be fairly simple, if I can find switches to do what I want.
I started tracking lines on the truck last night with no luck (too much paint), I need to start searching the TM's for a diagram.
I thought the front and rears of the M939's where already on two separate circuits, but from what I was seeing on the truck I'm having my doubts. Do big deal though either way.
Thanks, and good luck on your AC!
I'll have to read up on that, if I ever find a camper to make modular and put up on the back of my truck....

 

[74M35A2]

I'm not done trying, I still need to try the CAN bus termination resistors. Even if I can get it to work, it will only be useful for diagnostics and to change target pressure set points, which is still cool. The M939 CTIS is a single channel system. It has no idea how many tires it is responsible for, which is why I am going to connect it to the trailer I am making out of an M923A2 back half.

 

[Jbulach]

I'd be in for a fair deal of $ just to change the pressures!
Have you ever thought about if there's a way to trick the system on the pnumatic side into thinking its at a different pressure than it really is? I'm sure it's possible, but thinking it would take some very complex and expensive valving/ regulating?
I pretty sure if I get the manual system going I will make the front its own channel, so I can run the rears lower while empty.

 

[74M35A2]

Actually, this thread should be in the 5T mod section. Anyway, you could plot a curve of the pressure sensor vs resistance or output to the controller, and then switch out different value resistors to alter the pressure the ECU "thinks" the system is at. To do a dual channel, you would need 2 controllers and 2 ECU's, or manual valve control setups, unless you acquired a multi-channel from the civilian market.

 

[Jbulach]

Sooo... This could be as simple as putting a rheostat on one of the wires between the Ctis ECM and the electric over air valving ( don't know the technical name) that's inside the winch control housing??? Sorry, I guess I need to also post some of these questions on your CTIS reprogramming thread.

 

[Jbulach]

This is what I'm thinking, but... Of course I can't find a valve to do what I want!

This would let you use an adjustable regulator in the left position, relieve the pressure off the wheel cylinders when the desired pressure is reached in the center position, and the existing CTIS to function normally in the right position.

Anyone see any issues, or know of a valve like this?
If I have to, I guess I can use two 2-way valves or back the regulator all the way out every time, but really want to avoid that.


Sent from my iPhone using Tapatalk