Dryer under dash cycles over and over

[VikingatWar]

925a2 - dryer under dash cycles constantly once pressure is reached (120-125). No pressure loss really even at idle. Only cycles like this when CTIS ECU is plugged in. Unplug the CTIS ECU and no more dryer cycling. When plugged in cycles about every 2 seconds, stops every so often for about 10 seconds then starts again. Looks fine when taken apart and put back together.

Thanks for any input.

 

[capnkirk]

that's your CTIS controller. Might want to read up a little bit on the troubleshooting. Lots of useful threads on here already.

 

[VikingatWar]

I have read the TM concerning the operation. The Highway light flashes all the time indicating "correct" operation according to the TM but the dryer continues to cycle repeatedly. Also, I don't really see or hear any difference in tire pressure regardless of which button is pushed or how long it stays in each position.

Thanks.

 

[capnkirk]

Might try a gauge in line with the outlet of the CTIS controller. You may have a pressure switch somewhere that's AFU.

 

[VikingatWar]

OK, I'm thinking the pneumatic controller may also need to be tested.

 

[1 Patriot-of-many]

What freaken dryer under the dash? The pneumatic controller is supposed to repeatedly cycle until all tires are up to the proper pressure. Use the hand throttle, set it at 1500rpm or so, and let the pneumatic controller fill the tires, use that time to walk around and see if there are air leaks. If in 15 minutes or so, it hasn't stopped cycling you have a leak somewhere. I fail to see how you can determine by sight or hearing if the air pressure has changed....... Unless the tire was flat and now it isn't....

 

[VikingatWar]

Keeps moisture out of system? Makes no noise if CTIS is unplugged. If CTIS is plugged in, it spits a burst of air every 2 seconds once pressure is reached (normally 120 on both gauges). Highway light flashes as if all is normal.

 

[searls84]

That "freakin" air dryer should have no air coming out of it at all. Something is wrong with it, so repair or replace it.

 

[hklvette]

That "freakin" air dryer should have no air coming out of it at all. Something is wrong with it, so repair or replace it.

FWIW, since the truck should have a full-system air dryer (the Haldex unit inside the passenger frame rail) that you regularly service (right?), the air/water separator or "freakin' dryer" really shouldn't be necessary. In light of this, I'll be getting a double-ended compression fitting to eliminate that separator completely.

 

[searls84]

FWIW, since the truck should have a full-system air dryer (the Haldex unit inside the passenger frame rail) that you regularly service (right?), the air/water separator or "freakin' dryer" really shouldn't be necessary. In light of this, I'll be getting a double-ended compression fitting to eliminate that separator completely.

It's there for a reason. Not only is it an air water seprator, it also acts as a filter to keep rust particles etc. out of the PCU. When I picked my truck up from GL at Ft Bliss, TX (arrid dry dessert) that "unnecessary" seprator was clogged with rust particles that would have no doubt trashed the PCU if it wasn't there. So no, it is necessary and should be repaired or replaced.

 

[RustyM923]

Drill out the base and add a shraeder valve in place of the rubber disk and plastic pin dongle thing. Check it for moisture once a month. Or replace it. $40 or so.