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Key On

Was curious, I am thinking about adding a tee into my air line coming into the Air Dryer to allow me to hook up to an outside air compressor.  This way, while in my garage for the winter, I could still turn on the key and raise or lower the coach without having to start the engine.

My questions are :
When turning on the key, does that activate the Air Dryer ?
Will any harm be done to any components by leaving the ignition key in the "ON" position for a long time ?

If the above are okay, does anyone see any issues with this with the key on idea?

I saw the Tee Air Line on Rogers Coach and really liked it. 
Mark & Bev
2001 U295 36' Slide
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Key On

Reply #1 –
I have teed an air line in before the air dryer and when I am filling my tanks I put the key on. I wouldn't leave the key on 24/7.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Key On

Reply #2 –
Quote from: MarkC –
When turning on the key, does that activate the Air Dryer ?
AFAIK the only electric component on the air dryer is the 12 volt heater element on the purge valve.  Unless the coach is parked in below freezing temperatures, I don't think you need the ignition key on for the dryer to function.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Key On

Reply #3 –
Quote from: MarkC –

My questions are :
When turning on the key, does that activate the Air Dryer ?
Will any harm be done to any components by leaving the ignition key in the "ON" position for a long time ?


Not really.  The air dryer is cycled by a line from the D2.  It all works on compressed air.

The only components that could be harmed by leaving the key on with the engine not running are the ignition points.  Your diesel doesn't have ignition points.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Key On

Reply #4 –
I asked that question when I did mine. The answers I got made me think that it is only needed when cold.  The air coming into the dryer is already hot from the compressor.  It would be easy enough to add a switch and power it from the engine bay so you don't have to turn on the ignition. But then you have to remember to turn it off.

Be sure to use a 1/4 turn ball valve between the T and the incoming air connection.  I used a 3/8" x 3' air line with a female end.  That gave me another air stop.  I use a male to male adapter to make the connection to my external air compressor.  I noticed that the female end of the short hose gets really dirty so I added a cap to the fitting to keep the dirt out.

It works well.  If you are working on your air system and need to air up you can do it without running the engine and keep it pressurized while on the elusive hunt for leaks.  And when it gets to the appropriate pressure the purge valve does what it is supposed to do. 
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Key On

Reply #5 –
As others have said, I would NOT leave the ignition on 24/7. Depending on year model and coach wiring, the ignition ON may activate the fuel shutoff solenoid, may add engine hours to the hour meter, etc.

Sure, if you want to use an auxiliary compressor to provide air "pre-air dryer" in well below freezing conditions pretty easy to wire a second source of 12 VDC to the dryer heat element.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Key On

Reply #6 –
Quote from: wolfe10 –
As others have said, I would NOT leave the ignition on 24/7. Depending on year model and coach wiring, the ignition ON may activate the fuel shutoff solenoid, may add engine hours to the hour meter, etc.
Plus, you are activating the ignition solenoid, which in turn supplies power to a number of other circuits, including the HWH leveling system and the Allison CPU.  The leveling system will attempt to go to ride height, and if air pressure is low the alarm will sound continuosly.

IIRC the heater element on the air dryer purge valve is thermostatically controlled.  Even if hard wired to a separate 12V (fused) power source, the heater would only operate when ambient temps fall below the set temp on the control.

In other words, it would only work when it was needed, and would not draw power otherwise.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Key On

Reply #7 –
Thank you to all, I appreciate the information !!!
Mark & Bev
2001 U295 36' Slide
Cummins ISC 8.3 350HP
Build #5802
Jeep Wrangler Toad

Re: Key On

Reply #8 –
Not sure of this is helpful but I can air up my coach from the on board air hose...in reverse. I found a fitting I can use to hook up a portable air compressor to the end of the coaches air hose. I open the valve and fill her up.
1993 U300 40ft GV SE
Build # 4344

Re: Key On

Reply #9 –
That bypasses the dryer when you use a male to male adaptor.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean
 

Re: Key On

Reply #10 –
So any modifications to your air system deviates from the DOT certified system. Make sure everything you do is very robust and built to last the life of your coach. A failure will cause complete loss of being able to build air. Also you could find yourself having to represent your self and actions if your coach ever has a new owner. Dual flow stop devices? Precrimped high pressure flex lines, quality ball valve inline, quality hose line disconnect, physical functioning plug with lanyard. Large size is not needed. A 1/16 line will supply all you need just at a slower rate. I use mine all the time. Was one of the very first mods to my coach. I do keep key on time limited to a minimum, but better than running engine. IMO.
Scott
I would never recommend modifying any DOT certified system to anyone without manufacturers recommendation.