Low Air Pressure Switch Location

[Show 488]

Hi all, I’m starting to get very erratic low air pressure alarms on my 1988 40' 8V92. The Air pressure is always excellent when the alarm comes on, it seems to happen the most after the coach has been idle for a week or so. I suspect the Sw. has gotten moisture in the contacts, but after several searches, I can’t locate the Switch. Has anyone found this switch on their coach?

Thanks to all,

[Richard and Rhonda]

Have you looked at the primary tank, not the wet one? I think mine is mounted on the inlet to that tank.

Trace your brakes backwards.

[fulltiming]

Excellent point Richard. While it is likely that the brakes may still be up after a week, you would be fortunate indeed if your Supply tank hadn't lost enough air to get a low pressure light. You may not have as many air connections as the 1990+ models do but a coach that holds Supply pressure for over a week is a good tight system. Mine certainly won't.

There should be two gauges for air pressure, Brakes (which has 2 needles - one for the front tank pressure and one for the rear tank pressure) and Supply (which has a single needle). I just checked and I get a low air pressure light if the pressure in the Supply tank is below 65 psi even if the pressure in the two brake tanks is well above 65 psi. You should get a low pressure light if the pressure in EITHER of the brake tanks drops below 60-65 psi but that would be hard to verify because a leak from either brake tank should immediately be refilling from the Supply tank so the Supply tank pressure would be dropping immediately to equalize the pressure between it and the lowest pressure brake tank. There are check valves in each of the brake tanks to prevent them from bleeding back into the Supply tank.

[chockwald]

My coach loses air faster in colder temps, but seems to hold air a long time in the summer. Usually after 2 weeks in this weather my tanks are down to zero. In the summer after a month they were still at 60 psi.

[Wally Arntzen]

I have an 88 coach as well and if you are talking about the switch that is used when the vehicle is parked, mine is located in the air compressor compartment on the dirvers side of the coach in the front.
If you look at the compressor the switch is located on the wall panel in front of it near the top of the compartment. It is a limit control switch that you can adjust to provide air when the preasure drops. (I have mine set to come on when it drops to 60 pounds and go off at 90 pounds.)
The compressor that is in mine il limited to 100 pounds so can only go so far with the high end.
Check your switch to see if it is ok and if not I think you can get them a Grainger. I think I got from Newell parts department.

Good luck, Wally

[fulltiming]

Wally, the switch Richard is talking about is a low pressure switch located on or near the air tanks to warn of low tank air pressure.

The pressure control you are referencing sets the on-off pressure for the auxiliary 120 volt air compressor.

[Show 488]

Thanks Guys,
For the timely responses, I should have mentioned that this problem occurs while the Coach is operating @ 110 – 120 psi (which caused a great deal of panic the first time!) Richard, good call on the Pressure Switch being located on the Primary Air Tank, I’ll check tomorrow. I’m pretty confident that location will be correct, (don’t know why it didn’t occur to me!) Your guys are awesome!! Michael, on our last Coach, we once blew an air line apart in Gallup, Nm. & had just a few seconds to respond after the Cruise Control suddenly turned off (Non DDEC) before going into E-Brake lock-up. Your description of the Air Pressure indications & sequence of events are spot-on.
Wally, I recently renovated the Auxiliary Air Compressor and Compartment (still needs to be sound proofed with Dynamat) on Show 488, the Air Compressor is mounted in the compartment behind the Right Front tire, it never ceases to amaze me that these Coaches can offer so many different variants.
Clarke, Your coaches air system sounds like it very tight indeed!!
Again, thanks guys for all the great help. Will post the results.

Duanne

[Show 488]

Thanks Guys,
For the timely responses, I should have mentioned that this problem occurs while the Coach is operating @ 110 – 120 psi (which caused a great deal of panic the first time!)

Richard, good call on the Pressure Switch being located on the Primary Air Tank, I’ll check tomorrow. I’m pretty confident that location will be correct, (don’t know why it didn’t occur to me!) Your guys are awesome!!

Michael, on our last Coach, we once blew an air line apart in Gallup, Nm. & had just a few seconds to respond after the Cruise Control suddenly turned off (Non DDEC) before going into E-Brake lock-up. Your description of the Air Pressure indications & sequence of events are spot-on.

Wally, I recently renovated the Auxiliary Air Compressor and Compartment (still needs to be sound proofed with Dynamat) on Show 488, the Air Compressor is mounted in the compartment behind the Right Front tire, it never ceases to amaze me that these Coaches can offer so many different variants.

Clarke, Your coaches air system sounds like it very tight indeed!!
Again, thanks guys for all the great help. Will post the results.

Duanne

[tuga]

Duanne,

Just a reminder: block the coach with Jack stands or oak wood blocks BEFORE you get under it to work. These coaches have and will lose air and fall flat! Please be careful and good luck resolving your problem.

[chockwald]

Hi Duanne.....my air system may hold air a little better than the newer ones because the only thing air is used for in my coach is the braking, and suspension. No air operated doors, toilets, etc.....very low tech, and very few air lines and connections to worry about.

[Show 488]

Hi all, I spent the day searching the chassis of the Coach, the Low Pressure Switch is Located (at least on Coach # 180) above the Rear Air Storage tank, just forward of the Tag Axle, centerline in the Chassis. I removed the switch, and it was fully plugged with 21 yrs. of crud! It was mounted in the system clocked straight down, so any debris in the System gets trapped in it, the new installation will be in installed in the 12 “O” Clock position. After a complete cleaning, it’s still a little sticky, so a new one will be ordered tomorrow, P/n is Haldex BE13241, Cost is $19.13 + Shipping

http://www.ryderfleetproducts.com/cgi-bin/ryderfp/products/product_detail.jsp?BV_SessionID=@@@@2087320240.123 7160761@@@@&BV_EngineID=ccceadefmfhhlgfcfkmcgfmdfoldflm.0&oid=149848

Thanks Guys,
Duanne

[Show 488]

Replaced the Low Air Pressure Switch today, the System works great except the alarm comes on @ 72 psi vice 66 psi (as the Switch is rated). Reminds me that I might have spent a little too much time in the Navy!

Duanne

[fulltiming]

72 psi just gives you a little extra lead time. If the Low Air Warning comes on when traveling, 72 is still not a good number, just leaves a little more room before the spring brake comes on.

[Richard and Rhonda]

Nice post. I love it when the fix, and the link for the part get posted. Makes the forum a really good source for DIY.

Thanks and glad you got it taken care of.