dandick66

Ok. The compressor isn’t the easiest thing to get to, but I can access it. I see a .25 inch line running from the front tank to the Valid compressor tank. Out of the compressor, there’s a “T” to the Valid tank and a 3/8 line that runs to the front, rear and tag manifolds. Could I just plug the .25 and 3/8 lines temporarily and bypass/eliminate the compressor?

I haven’t seen that thread, but I’ll search for it. Looking at my air system diagram, the supply to that compressor is only connected to the front tank. Would it cause the rear tank to drop, too?

Yes, I have the compressor disabled. I mounted a switch near the dash and test it periodically.

Yes, Vaild leveling system VTL01K049

UPDATE 22 MAY I installed the new replacement pressure control check valve on Friday 19 May - the first one I received was defective. I started the engine and the pressure built up to 127 PSI. The rear tank dropped about 10 PSI, thereby indicating the valve is functioning properly. I drained the wet tank and both the front and rear tanks held pressure. I drained the front tank and the rear tank held pressure. Then I drained the rear tank and the front tank held pressure. I did restart the engine and let pressures build up between each scenario. Here is the timeline and pressure readings I recorded. 19 May 1430 Front 126/Rear 118 (Following governor cutoff and regeneration). 19 May 1910 Front 111/Rear 104. (Approximately 5 hours, 15 PSI drop front, 14 PSI rear) 20 May 0630 Front 91/Rear 91. (Approximately 11 hours, 20 PSI drop front, 13 PSI rear) 20 May 1900 Front 79/Rear 79. (Approximately 12 hours 12 PSI drop front, 12 PSI rear) 21 May 0700 Front 67/Rear 67. (12 hours, 12 PSI drop front, 12 PSI rear) 21 May 1830 Front 59/Rear 59. (Approximately 12 hours, 8 PSI drop front, 8 PSI rear) 22 May 0700 Front 49/Rear 49. (Approximately 12 hours, 10 PSI front, 10 PSI rear) I’m not exactly sure what my data indicates. It appears that the front tank dropped pressure a little faster than the rear until they equalized and then they dropped pressure equally. It leaks about 1 PSI/hour. I don’t know the accuracy of the transducer and gauges, but I’m assuming it’s +/- 2 percent. I have not installed the new spring brake hose yet, but I don’t think that affects any readings since it has no pressure when the parking brakes are engaged.

My 2012 Diplomat is Rev 1.2. Like Ivylog said - ignore it… Tom, Have you ever seen “HIGH BATTERY “ displayed on the Medallion? Mine did it a couple of times and the engine will crank, but not start. Cycling the ignition key several times usually cleared it. The last time it did it I connected the Navistar Diagnostic software and discovered that it was low power to ECM. I found a relay that was sticking and not allowing 12 volts to the ECM. Apparently, Medallion takes the J1939 data and converts it to whatever they want. They could have the message say “Good Morning “ if they wanted to. I replaced the relay and all has been good since.

Not sure if everyone is aware of sign placement on interstates. I’ve had exits “sneak up on me”, but I try to be a little more attentive when I know I’ll be exiting soon.

I stopped at the one in Florence (in my pickup) just to see what all the hype was about l. I figured out why they have so many pumps - no one uses the parking lot. They just leave their cars at the pump and go shopping and dining. I don’t know if I’d try to go there with the coach. It’s a mad house. I just found out they’re building one here in Virginia, or too far from me. It will be on I 64 between Richmond and Williamsburg.

I found another place that has the 1/2 inch hose. I am going there in Wednesday to get the hoses made. I didn’t think about the ABS aspect, but was going to use the 1/2 inch hose for commonality. Thanks for pointing that out.

I reinstalled the old valve today. The air dryer is regenerating now as it’s supposed to. Unfortunately, the check valve portion of it is bad so when I drain the wet tank, the rear tank drains, too. The regeneration process is removing the oil from the dryer, because I’m not getting any oil when I drain the tank with the old valve. I’ve ordered a new valve, so I’ll get it installed as soon as it are. It’s too bad I can’t take the working portion of both valves and have one good valve. There was some success today. I found one of the hoses from the inversion valve to the spring brake chamber was leaking. That explains why I was losing some pressure while driving. That was another learning experience. I went to the local NAPA to get a new hose made, only to find out they can’t make the hoses. Apparently, you have to be DOT certified to make the hoses. I went to a truck shop and he only had 3/8 hose and male fittings. Monaco (at least my Diplomat) uses 1/2 inch hose with female swivels. They installed nipples on both the chamber and inversion valve- I have no idea why Monaco did it this way. I think I’m beginning to see light at the end of this tunnel. I just hope it’s not a train coming towards me…

The wet/front tank is behind the front axle and is easy to work on. The rear tank, where the valve is, is above the differential and it’s a challenge to get to.

I’ll put the old valve back in tomorrow. I assumed that it was working as it’s supposed to since it was preventing the air from flowing back through the wet tank to the front tank.

It’s very similar. Here is the one I used. It’s the same model as the one I took out. I placed it on the rear tank, which I think is called the primary tank. https://www.haldex.com/en/na/air-dryerair-line/air-dryers/competitive-newremanufactured/wabco-ss1200-repair-kits/s4341003100/ Bill, I don’t think it’s working at all. I am getting oil in my wet tank now. From what I’ve read, that’s the regeneration valve not working. The weird thing is that it was regenerating before I replaced the valves. Before I replaced the valves, both tanks would drop approximately 10 PSI after the compressor cut out. I found out that only the rear tank should have dropped the 10 PSI. That was a result of the failed pressure protection valve. The Haldex manual indicates the problem could be the governor or regeneration valve. I have a spare governor and I think I’ll change it out tomorrow. The regeneration valve kit is pricey- around $250.

Update I got the new shuttle valve and pressure control valve installed yesterday. I used Loctite Blue on the threads and it call for 24 hours to fully cure. I waited until this afternoon to start testing. I’m happy to report that the new valves are working as they’re supposed to. When I open the wet tank drain, only the wet tank pressure drops. When I open the front tank drain, the front tank pressure drops and the wet tank and rear tank pressures hold. When I open the rear tank drain, the wet tank and rear tank pressures drop and the fron tank pressure holds. Now the bad news. For some reason the air dryer is not regenerating. The pressure is supplied to build to approximately 125 PSI, then drop about 10 PSI for the regeneration cycle. I am not getting the pressure drop. The WABCO manual says the problem could be the governor or the regeneration valve. It’s weird that the regeneration process worked fine until I replaced the shuttle valve and the pressure control valve. More troubleshooting tomorrow… Dan

I will do a postmortem once everything is fixed. Before I started all of this testing, whenever the governor cut out my front and rear pressures would both drop 10 PSI. I thought that was normal. Now, with the shuttle valve removed and line plugged only the rear tank drops 10 PSI. I’m learning more every time I crawl under there…

New Testing today 09 May I removed the shuttle valve/2 way check valve and plugged the output from the dry tank (this was 1 of the inputs to the shuttle valve). I plugged the silver 1/2 inch hose that was the other input to the shuttle valve (from rear tank). I left the green 1/2 inch hose unattached- I think it goes to the spring brake relay). I started the coach and let it build up pressure until the governor cut out. I noticed that the 10 PSI drop that normally occurs after governor cut out only affected the rear tank - the front tank held at 125 PSI. Next, I opened the wet tank drain. The rear tank pressure dropped, but the front held. I confirmed the rear tank drained by opening the valve at the rear and there was no pressure. I cracked the front tank dry drain to confirm it was still full/holding. I started the coach again and let the pressure build up. I opened the rear drain and the rear pressure dropped and the front pressure held. After the rear tank emptied, I cracked open the wet drain and there was no pressure. I cracked the front tank dry side drain valve to confirm it was still full/holding. I started the coach again and let the pressure build up. I opened the front tank dry side drain and both front and rear tanks dropped pressure. I opened the wet tank drain and there was no pressure. I believe this testing confirms that the wet/dry internal check valve is working properly. I will install the new shuttle valve and new charging check valve when they arrive. I’ll post the results. Dan

Is the top in the photo for filling the tank? On my coach the fill fitting has a valve behind it for draining the wet tank. Under that is the front tank drain. The rear tank drain is back next to the trailer hitch. My valves are supposed to get here Thursday. In the meantime, I might put a plug in the front tank where the shuttle valve was and then plug the line coming from the rear tank. I think then I can test the set/dry check valve.

Frank, Thanks for keeping me straight. I’ve order the new shuttle valve and rear tank check valve. Once I get the shuttle valve replaced, I’ll post the results and then go from there.

Frank, Thanks for the information. I took the valve apart and cleaned it and blew in both inlets and the shuttle moved back and forth as it’s supposed to. I reinstalled it and started the engine to fill the tanks. I think my check valve stuck again because no matter which drain valves I opened, the front, rear and wet tanks drained. I guess the tank will have to come out. Do you know if the check valve has a part number on it? Jim, Thanks for the suggestion. I live in Virginia between Richmond and Norfolk, so I’m sure there is somewhere to get new fittings. It’s going to be a busy week…

Well, I finally got the shuttle valve removed. I had to cut one of the hoses because the PTC connector would not release. After I got the valve out of the tank, I looked at it and figured out how it works. It makes more sense when you can actually see something. The name doesn’t do it any justice - 2 way check valve. I’ve attached a photo of the valve. Tomorrow I tackle the valve at the rear tank - I think….

What I mean is I filled the tank at the “fill valve” using an external compressor, so the air went to both the front and rear tanks. Sorry for the confusion…

Ok, here are my latest test results for the tanks. I filled the wet side to 110 front and rear. I opened the rear drain and the rear dropped to 0 and the front tank held at 110. I repeated this test 5 times with the same results each time. Next I filled the wet side to 112 front and rear. I opened the dry side drain and both front and rear tanks dropped to 0. I repeated this test 5 times with the same results each time. Next I filled the wet side to 112 front and rear. I opened the wet side drain and the front held at 111 and the rear dropped to 0. I repeated this test 5 times with the same result each time. So, it looks like when I moved the 3/8 extension around the inside of the wet tank I must have unstuck the check valve. Now I need to get the hoses off of the shuttle valve and replace it, then find the valve at the other end of the 5/8 hose coming out of the wet tank and change it out.

I think that’s one thing I didn’t check. If I open the rear drain, the front holds pressure, but I think that’s the dry side. Tomorrow I’ll see if the wet tank holds air if I open the rear valve. I doubt it will because when I drain the wet tank, the rear tank goes to 0. You’d think the result would be the same if I drain the rear. I’m going to post my test results in a little while. I did look at the shuttle valve. I think on my diagram it’s called a two way check valve. The part number on it is 157A1A. I can’t seem to get the hoses off. I’ve tried pushing with open end and flare wrenches and no joy. I’ve done the /4 inch hoses before, but these are 1/2 inch. I still need to find the charging check valve in the rear. I assume it will be at the other end of the red hose coming out of the wet side.

Not sure what the DIC is, but here’s the control panel and dash/display.

I did not know that about the Medallion system. When I turn the key on and try to select any readings, nothing happens. I just tried again, but this time I hit “enter” and was able to access all of the screens. Thanks! However k if I start the engine and the pressures are low, I get the low air display and cannot clear it until the pressure bulbs to approximately 75 PSI. I lowered the coach and was able to access the plug on the wet side of the tank. I figured out why you can’t use a 3/8 socket to access the valve - it won’t fit into the drain plug hole. The dividing plate is about 19 inches into the wet side. I took the socket and extension and fumbled around, but could not get it onto the valve, so, put the plug back into the side. I’m definitely going to have to drop the tank. I still am not having any luck removing the PTC fittings. I have tried the flare nut wrench trick, but no joy. I’m afraid I’m going to break the line at this point. I started the coach to raise it back up off of the stops. Now, when I drain the wet tank the front tank pressure holds! The rear tank still drops pressure. I tried it 3 times and it was the same. When I open the front (dry) tank, pressure drops in both front and rear tanks. When I open the rear tank, only the rear drains. I don’t know if I “unstuck” the valve when I poked around with the extension. I need to run some errands this afternoon and then I’ll try again this evening. Even if it gets good, I think I still have the problem with the shuttle valve. I still need to find a way to get those #$#&& PTC fittings apart.