Gary M Posted June 30, 2022 Share Posted June 30, 2022 Pulled into new spot for about another week. Spent two days with wife in emergency (all ok). Today decided to set up. Fired up engine to build up pressure to extend slides. Pressure was at 93 lbs and built up to 123 before slowly dropping to 111 lbs. Holds steady there but will not raise and no popping of at dryer. Have 40 miles up into mountains to my home base. Where should I be looking for this issue? Would it be safe to finish to destination in a week if issue is not solved? Link to comment Share on other sites More sharing options...
KevinH Posted June 30, 2022 Share Posted June 30, 2022 Last time I had a similar problem it was the air governor 1 Link to comment Share on other sites More sharing options...
JohnC3 Posted June 30, 2022 Share Posted June 30, 2022 Just a couple of thoughts. Compressor usually has a cut in pressure. 111 may be too high for the compressor to engage. Try hitting your brakes ancouple of times. Mine cuts in around 75-80 and cuts out around 115. At what pressure do you normally hear the air dryer chuff? Mine will get to about 120 rear and 115 front then chuff and drop to 115/110 as the air dryer is regenerating. Other than not hearing the chuff, your account could be normal operation. There is no air control board, it is all controlled by air pressure, springs and diaphragms (on my rig at least). I would pump the brakes to lower the air pressure to see if it will charge up above 111. If you should be at higher pressure, my money is on the compressor governor (sets the purge/chuff pressure)or the air dryer preforms the purge. 1 Link to comment Share on other sites More sharing options...
Gary M Posted June 30, 2022 Author Share Posted June 30, 2022 1 minute ago, KevinH said: Last time I had a similar problem it was the air governor I’ll check to see where it’s at on my 360 Cummins. Maybe give it a thump? Link to comment Share on other sites More sharing options...
JohnC3 Posted June 30, 2022 Share Posted June 30, 2022 One other thought, ony rig I need 65 psi to work the brakes (make them release) as I recall. If you can maintain pressure above the amount needed to use your brakes and the compressor will pump air into the system, then you should probably be ok to proceed, but I would get it looked at asap. If your pressure drops too low, your brakes will engage (and without the air pressure to release them)and you will need to be towed. 2 Link to comment Share on other sites More sharing options...
Gary M Posted June 30, 2022 Author Share Posted June 30, 2022 2 minutes ago, JohnC3 said: Just a couple of thoughts. Compressor usually has a cut in pressure. 111 may be too high for the compressor to engage. Try hitting your brakes ancouple of times. Mine cuts in around 75-80 and cuts out around 115. At what pressure do you normally hear the air dryer chuff? Mine will get to about 120 rear and 115 front then chuff and drop to 115/110 as the air dryer is regenerating. Other than not hearing the chuff, your account could be normal operation. There is no air control board, it is all controlled by air pressure, springs and diaphragms (on my rig at least). I would pump the brakes to lower the air pressure to see if it will charge up above 111. If you should be at higher pressure, my money is on the compressor governor (sets the purge/chuff pressure)or the air dryer preforms the purge. Mine purge’s around 122-123 and settles down to 117-119 while driving. Now that I’m supported by jacks I’ll drop the pressure below 65 at which low alarm activates and see if she will rise to the occasion. Hmmmm!! Link to comment Share on other sites More sharing options...
det944 Posted June 30, 2022 Share Posted June 30, 2022 25 minutes ago, Gary M said: Probably different but my 2006 Dynasty (ISL 400) operates exactly as John C3 states in his first post. I do not have hydraulic Jack's. 1 Link to comment Share on other sites More sharing options...
timaz996 Posted July 1, 2022 Share Posted July 1, 2022 When was the last time you had the air dryer serviced? Tim Link to comment Share on other sites More sharing options...
Gary M Posted July 1, 2022 Author Share Posted July 1, 2022 2 hours ago, Tim-AZ said: When was the last time you had the air dryer serviced? Tim 9 mo ago Link to comment Share on other sites More sharing options...
Frank McElroy Posted July 1, 2022 Share Posted July 1, 2022 Gary, attached is a good pre-trip check list for air brakes. See how your system performs especially under step 3. This should help you decide if the coach is safe to drive. Link to comment Share on other sites More sharing options...
96 EVO Posted July 1, 2022 Share Posted July 1, 2022 If your system normally unloads at 123psi, I wouldn't expect to see it build pressure again till it drops to about 100psi. You will usually lose about 10psi right after unloading (regen cycle), then you will usually have another 15psi for braking / suspension etc, before the governor will close your compressor valves. 1 Link to comment Share on other sites More sharing options...
Gary M Posted July 1, 2022 Author Share Posted July 1, 2022 (edited) 6 minutes ago, 96 EVO said: If your system normally unloads at 123psi, I wouldn't expect to see it build pressure again till it drops to about 100psi. You will usually lose about 10psi right after unloading (regen cycle), then you will usually have another 15psi for braking / suspension etc, before the governor will close your compressor valves. Normally after I start engine and no matter what psi is at, it unloads at 122-123psi and then drop to 112-113 then build up to 118-119. I brought rpm’s up but it would not raise pressure at all. Edited July 1, 2022 by Gary M Link to comment Share on other sites More sharing options...
96 EVO Posted July 1, 2022 Share Posted July 1, 2022 5 minutes ago, Gary M said: Normally after I start engine and no matter what psi is at, it unloads at 122-123psi and while rim doing checks it will unload several times more by the time I get in to drive. I assume that’s normal!!! I'm guessing your using air filling your air bags during this time? Those of us with air leveling are a little different. We start our engine and the suspension stays where it is till we press 'travel mode', so, if I start my engine and my air pressure is above 100psi, it doesn't build and purge. Link to comment Share on other sites More sharing options...
Gary M Posted July 1, 2022 Author Share Posted July 1, 2022 46 minutes ago, Frank McElroy said: Gary, attached is a good pre-trip check list for air brakes. See how your system performs especially under step 3. This should help you decide if the coach is safe to drive. Thanks Frank👍 Link to comment Share on other sites More sharing options...
Frank McElroy Posted July 1, 2022 Share Posted July 1, 2022 Based on what you described, it sounds like your system is functioning normally. Running through a brake pre-trip checklist will let you know for sure that the system is operating the way it should. 1 Link to comment Share on other sites More sharing options...
Gary M Posted July 1, 2022 Author Share Posted July 1, 2022 38 minutes ago, Frank McElroy said: Based on what you described, it sounds like your system is functioning normally. Running through a brake pre-trip checklist will let you know for sure that the system is operating the way it should. Yes but why won’t it build pressure from 111 with rpm’s up just sitting. Unless my memory is off it should build up. 1 hour ago, 96 EVO said: I'm guessing your using air filling your air bags during this time? Those of us with air leveling are a little different. We start our engine and the suspension stays where it is till we press 'travel mode', so, if I start my engine and my air pressure is above 100psi, it doesn't build and purge. Well unless my memory has failed, when ever I raised rpm my pressure would build to max and then purge. Link to comment Share on other sites More sharing options...
Frank McElroy Posted July 1, 2022 Share Posted July 1, 2022 52 minutes ago, Gary M said: Yes but why won’t it build pressure from 111 with rpm’s up just sitting. Unless my memory is off it should build up. Well unless my memory has failed, when ever I raised rpm my pressure would build to max and then purge. The likely reason why the compressor didn't cut in at 111 is that you are still a few psi above the cut in pressure. Try pumping the brakes once or twice and I think you will hear the compressor start and build pressure. Engine RPM does not control the compressor cut in and cut out pressures. The governor does. Higher engine RPM will cause the compressor to build pressure faster. On my coach the cut in pressure is 108 and the cut out pressures is 134. 2 Link to comment Share on other sites More sharing options...
96 EVO Posted July 1, 2022 Share Posted July 1, 2022 Yep, I'm with the others! You're not going to know if you have a problem till you get your tank pressure below about 100psi. 1 Link to comment Share on other sites More sharing options...
Doug and Nicki Posted July 2, 2022 Share Posted July 2, 2022 I just had to replace my air dryer for a leak a few weeks ago. However, I could hear mine. While at it, I fixed another leak at a fitting. 1 Link to comment Share on other sites More sharing options...
Gary M Posted July 4, 2022 Author Share Posted July 4, 2022 On 6/30/2022 at 9:30 PM, Frank McElroy said: The likely reason why the compressor didn't cut in at 111 is that you are still a few psi above the cut in pressure. Try pumping the brakes once or twice and I think you will hear the compressor start and build pressure. Engine RPM does not control the compressor cut in and cut out pressures. The governor does. Higher engine RPM will cause the compressor to build pressure faster. On my coach the cut in pressure is 108 and the cut out pressures is 134. Low Air Pressure? 09 Knight 38PKQ. Update: Dropped pressure down to 60 lbs and then raised rpm. Pressure built up to 122 and dryer purged. Let engine idle and pressure slowly dropped to 111 again and held there. My next test will be the air brake pre tip test. Link to comment Share on other sites More sharing options...
Gary M Posted July 4, 2022 Author Share Posted July 4, 2022 On 7/1/2022 at 9:59 AM, 96 EVO said: Yep, I'm with the others! You're not going to know if you have a problem till you get your tank pressure below about 100psi. Dropped pressure down to 60 lbs and then raised rpm. Pressure built up to 122 and dryer purged. Let engine idle and pressure slowly dropped to 111 again and held there. My next test will be the air brake pre tip test. Link to comment Share on other sites More sharing options...
96 EVO Posted July 4, 2022 Share Posted July 4, 2022 So far, so good 👍! Link to comment Share on other sites More sharing options...
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