1998 U-320 36' M11 Celect Plus
I was finally able to get under the coach today and check for air leaks on the front six pack.
One of the 10 PSI Hobbs pressure switches has a constant leak at the end of the unit where the rubber cap is located. The photo below is from Chuck & Jeannie's six pack thread from a couple years ago.
Does this mean that the unit has failed and needs to be replaced?
Thank you.
Chris
Chris,
The short answer "Yes"
The pressure switches can be gotten at some parts stores just take the old one in to see if they can match it up.
Mike
Mike,
Thank you for the reply.
Chris
Honeywell - 76578-10-01 - 0.5 A (Inductive) 1 4 A (Resistive) 8 15 10 PSI... (https://www.alliedelec.com/honeywell-76578-10-01/70111621/)
Mark
Excuse my ignorance, but what is the purpose of this pressure switch?
https://www.hwhcorp.com/ml20635.pdf (Page 19, System Pressure Switches)
"The front air pressure switches on all 600 and 680 Series Leveling Systems are used during any lower functions, manual operation, automatic operation or use of the "DUMP" button. When the pressure switch for a front bag turns on, it sends a ground signal to the control box. This will inhibit the opposite side front air bags from lowering.
EXAMPLE: While pushing the right side lower button, the right front air pressure switch sees low air pressure. The front lower button is then pushed. The right front lower solenoid valve will turn on and open, but the left front lower solenoid valve will not turn on. The left front bag will not lower. This is done to prevent the front of the vehicle from twisting. If one side of the front of the vehicle is as low as it can go, lowering the other side will twist the vehicle."
Thanks Chuck.
Received the new pressure switches today (replacement plus one spare), got it installed (not easy), and am doing a leak test right now.
Removing the old pressure switch was not easy. The threaded end of the switch had fused to the 45 degree brass fitting. I didn't want to remove all the other air line components on the six pack (7 more chances for something else to go wrong). I ended up cutting the pressure switch off between the brass fitting and the base of the switch using a small hack saw. Once the switch was off it was easy to remove the old 45 degree brass fitting.
New fitting and new pressure with were installed using yellow teflon tape (gas rated tape) and the joints passed the soap bubble test.
Chris
Chris,
I'm not criticizing or second guessing your work, but most of our more experienced "tech" members recommend using a thread sealing paste on air system fitting, rather than tape. Doing so reduces the chance of introducing a stray bit of tape into the air lines, where it might end up fouling one of the valves. Just something to consider next time.
I've had good luck with Permatex - found in most auto parts stores. 6 ml tube will last a long time.
Amazon.com: Permatex 59214 High Temperature Thread Sealant, 6 ml Tube:... (https://www.amazon.com/gp/product/B0002UEOP0/ref=oh_aui_detailpage_o03_s00?ie=UTF8&tag=foreforums-20&linkCode=as2&camp=1789&creative=390957&th=1)
How many of these low pressure switches are used through out the entire system?
As old as my coach is I'm sure all this stuff needs to be replaced before it eventually fails.
I would not proactively replace them. If you have symptoms OR if you do a "soap bubble" test on the fronts 6 pack, replace the "bubblers".
2 - on the front 6-pack manifold.
Two low pressure switches on the front, and the one on the rear six-pack (attached to the bottom of the manifold) is a 'whole system' pressure switch with a different range than the ones on the front manifold.