Community Forums

ardbark · 04-17-2012, 11:45 AM

While setting up camp last week I dumped air to lower the coach. No big deal. But while breaking camp and warming up my air pressure was down to 60-ish, the low air warning buzzer was screaming and it took a VERY long time to just get to 100. I've always lost a few pounds while parked but never down to 60 and it always built back up in just a few minutes of idling.

I usually run around 130 on both air systems but now, even after being at speed on the road for some time I'm not much above 100psi.

I'm running a 1996 36' HR Endeavor DP on an X-Line 4 bag Freightliner chassis. It might be just a coincidence but this is the first trip I've felt the need to dump air at camp and the first time I've had a pressure problem.

The only change I've made to the MoHo was the addition of a trailer brake controller. Also on this same trip I started seeing some strange electrical issues, e.g. guages bouncing around, dash heater blower acting squirrley, etc. I can't see how this could be affecting the compressor, but Murphy being who he is, well...

Any troubleshooting advise would be appreciated. The moho is approaching in-op with air pressure this low and DW has another trip planned for us next month. And we all know that we can't disappoint DW

BCooke · 04-17-2012, 01:06 PM

Going to have to get under the coach and listen for air leaks. A bleeder stuck (dump valve), line that got pinched, hopefully not a bag having an issue. (My father had one that let go and he found out when he tried to air up the next morning)
Dump valve could just not be seating properly.

wb7auk · 04-17-2012, 02:23 PM

Had almost the same deal air worked good then the next time could not get over
80 lbs. Problem found manual air bleed cables fouled in jacks not letting one of
them totally close valve. After a few nice words said about the truck shop that
routed them that way corrected the issue and works fine now.

jlfbatonrg · 04-17-2012, 03:12 PM

There is an air pressure control valve on the compressor that can go bad and cause the same problem. Another relatively common problem on some of the older coaches is the air line from the compressor to the air filter runs over the transmission and can rub causing a small hole that will lose air. As to the bouncing gauges, I would suspect a loose ground. I would check the grounds carefully.

Jim

ardbark · 04-17-2012, 05:15 PM

Quote:

Originally Posted by wb7auk

Had almost the same deal air worked good then the next time could not get over
80 lbs. Problem found manual air bleed cables fouled in jacks not letting one of
them totally close valve. After a few nice words said about the truck shop that
routed them that way corrected the issue and works fine now.

funny you should mention jacks, the jacks seemed to take for-ever to retract on this trip. Usually I have to be carefull with the joy stick or the jacks will slam back in to place, this trip it took so long for the jack warning light to go out I actually crawled under to watch them e-v-e-r s-o s-l-o-w-l-y retract back to the up position.

But aren't jacks hydraulic? I would never have put the two symptoms (low air/slow jacks together.

wb7auk · 04-17-2012, 05:17 PM

On mine they are retracted by springs that should not have cable from the air
dump valves in them. Ha Ha

ardbark · 04-17-2012, 05:19 PM

Quote:

Originally Posted by jlfbatonrg

There is an air pressure control valve on the compressor that can go bad and cause the same problem. Another relatively common problem on some of the older coaches is the air line from the compressor to the air filter runs over the transmission and can rub causing a small hole that will lose air. As to the bouncing gauges, I would suspect a loose ground. I would check the grounds carefully.

Jim

I think you're right and I've already convinced myself that the strange electrical stuff is probably a bad ground. Now to find the culprit out of the 752 ground points on my moho

EngineerMike · 04-17-2012, 05:30 PM

You can check this guy's thread on low air. He worked his way thru just about every cotton picking thing that might cause it, and I was amused (since I was not him) at the number of possibilities. Once you get a short list, the diagnosis should be easy.
Off chance you may find there is more than one leak, and the compressor was making up for the minor one(s), but one just started to exhibit big time.

Yes jacks are hydraulic and separate from air issue. try a rub-down on extended jacks w/transmission fluid; clean them w/it first, then rub down w/a dry rag. Most folks find that cures a new-to-them slow jack return.

ardbark · 04-17-2012, 08:01 PM

Quote:

Originally Posted by EngineerMike

You can check this guy's thread on low air. He worked his way thru just about every cotton picking thing that might cause it, and I was amused (since I was not him) at the number of possibilities. Once you get a short list, the diagnosis should be easy.
Off chance you may find there is more than one leak, and the compressor was making up for the minor one(s), but one just started to exhibit big time.

Yes jacks are hydraulic and separate from air issue. try a rub-down on extended jacks w/transmission fluid; clean them w/it first, then rub down w/a dry rag. Most folks find that cures a new-to-them slow jack return.

EM
Just read through your linked thread. I don't think my '96 4-bag Endeavor is anywhere near as complicated as a 2006 Alpine but OMG - I hope that story isn't me. I enjoy a challenge as much as the next guy but 4 years of the same problem is way beyond my patience level.

I'm going to run her for as long as it takes to get some pressure and do the crawl tomorrow. Hopefully I will hear a nice gentle hissing sound on a loose fitting in an easy to reach location (yea right, what's the chances of *that* happening :-)

I missed the part of Art's post about having a bleed cable tangled in a jack, hence my confusion. I haven't touched any of those systems so I doubt it will be that easy, but while I'm down there tomorrow I'll spruce up the jack pistons, which was on my Spring list anyway.

Thanks for the link, waaaaayyyyy more info than I ever want to know

ardbark · 04-18-2012, 09:29 AM

Its raining here today, so I won't be doing the crawl listening for leaks, but its given me time to think. I've always been of the opinion that when something goes south my first step in troubleshooting is "what's changed?" from the baseline when all systems were working.

And something did change on this trip, I added a new Primus IQ electronic trailer brake controller. Although I can't imagine how it could be the problem, it does interact with my brakes and my brakes obviously operate on air, and air is my problem, so here goes...

The controller takes its signal straight off the brake light switch, which is hanging off an air control module attached to the service brake pedal. We also snagged power from one of 4 ignition-switched hot posts that were located near the Onan genny. Each of these posts has multiple wires coming off of them, it appears to be a kind of distribution point for hot wires and I have no idea which systems are fed off the post we stole power from.

Is it posisble that somehow by tapping into the brake light switch we've upset some line impedence, or cross-connected some control circuit that is leaving some monitoring air valve slightly open or.... well, who knows?

The guy that installed the unit is a pro, trailer wiring is all he does, but by his own admission he sees very few motorhomes and even fewer DPs. I know I'm grasping here, but adding the controller is really the only thing that changed.

I'll disconnect the new controller and see if things change, but has anybody seen or heard of any issues with slaving in a controller and buggering up other systems in the process?

wb7auk · 04-18-2012, 09:38 AM

Anything is possible and the time you think no way not possible you find out oh yes
it is.

Skip426 · 04-20-2012, 11:41 AM

I'll agree that Murphy is in the building ; and throw in my 2c worth. The dash on my coach gets all it's info from the VIM ( vehicle information module ) in the engine bay. Via a data link connection, a twisted pair of wires from the engine bay to the front of the coach. If the installer disturbed the VIM ground in the engine bay ; rear frame rail area; or hooked into the data link wiring by mistake , all the dash readings/warnings will be haywire. The power posts you discribe , should be 1 chassis batt power 2 coach batt power, a cross feed through the controller between the 2 can also give you problems.
Was your coach pre-wired , front to rear for the controller ?
Or did the installer run his own wiring to the trailer connector ?
If the installer had the trailer connector apart, look there first.
When it comes to wiring issues , I'd rather be lucky than good !
So Good Luck.
PS. I'm trying to find out why my fuel gauge reads a 1/4 tank high when my headlights are on, and not making any progress.
Contact Freightliner help line for wiring diagrams, have your serial # when you call. Join Access Freightliner, tons of good info there too.

Skip426 · 04-20-2012, 11:53 AM

ardbark; on re-reading your post #10,

I see your working off ignition power posts, a disturbed connection there may result in poor/low power to other systems, so carefully test all other wires on the post for full battery volts.

EngineerMike · 04-20-2012, 12:05 PM

I'm guessing the only electrically operated air anything is the air dump on leveling. So if that isn't involved, the 'something new' hasn't touched air system. One of the fun things about diagnosing a DP issue, is that DP's have a lot of potential stuff in the mix. But I'm stuck on connecting the brake controller to the air system.
Now if you had one of those air-to-the-trailer setups......