I did some major service to the coach in the last few days. I bought the Bendix AD9. I read from few posts that the AD9 is a direct replacement of AD4.
But today, I went down the coach, I think it is not a direct replacement. I searched the forum found this post (https://www.foreforums.com/index.php?topic=23194.25)
In
@prfleming response @38 (https://www.foreforums.com/index.php?topic=23194.msg237017#msg237017),
Had to rewire the heater wiring for a 2 wire connection.
Then
@wolfe10 mentioned few message below
What is the part number?
I searched and found this (https://www.finditparts.com/products/1718619/bendix-109869n)from find it parts
Is this the right parts?
The old AD4 has just one wire. If I use this two wire, where can I connect the other wire to? the frame?
Other than the wire, is there any fitting needed to update AD4 to AD9?
I saw few people updated from AD4 to AD9, but I couldn't find a post detail the update procedure.
Thanks
1. Yes - 109869N looks like what you need, at a good price. I found a similar part in several other places, and they all look basically the same.
https://www.napaonline.com/en/p/MBI109869K
Amazon.com: Bendix 109871N Air Dryer Wire Harness and Splice Kit: Automotive (https://www.amazon.com/Bendix-109871N-Dryer-Harness-Splice/dp/B008LB1RVG)
2. The little heater in the bottom of the dryers is thermostatically controlled by an internal switch. The single wire to the old AD4 heater is
probably HOT whenever the ignition switch is on. Easy to check with a test light or your multimeter. So, if that is the hot wire, then the other wire in the new pigtail will go to any convenient nearby ground. The kit may include a installation diagram.
3. From my quick scan of the Forum archives, I don't think so. However, every "upgrade" project can be different, so be prepared to make a run to the parts store if necessary.
On second, third, and subsequent thoughts I feel I must modify my answer #3 in post above.
I was looking at some old photos from when I replaced our AD-9 dryer for the first time. The photos reminded me of a complicated Forum discussion back then concerning the Haldex Isolation Valve. This valve is found on some AD-9 dryers mounted on some Foretravel models with some turbo charged engines. My coach has one. See link below for one discussion with photos:
Air compressor blowing oil into dryer (https://www.foreforums.com/index.php?topic=40477)
The Isolation valve is not a part of the dryer. It is a separate piece that attaches to the inlet port of the dryer. A new or rebuilt AD-9 dryer will not include this valve.
The BIG question in my mind: Does your coach with a 6V92 engine, when upgraded to the AD-9 dryer, require the isolation valve? I cannot answer that question. Hopefully, some other Forum members with the same 6V92 engine (Andy 2 or Kent Speers or Pierce & Gaylie Stewart?) will know the answer. Sorry to throw this wrench in your upgrade plan, but I don't want you to omit this valve if, in fact, your engine/air compressor combination does actually require it.
See link below for more info:
Foretravel Motorhome Air Dryer Haldex Isolation Valve | All Things Foretravel (http://www.allthingsforetravel.com/2020/02/28/air-dryer-haldex-isolation-valve-2/)
After reading a post about the isolation valve issue, being proactive and keeping spares I bought a new one only to find out my coach doesn't need one. It sits on the shelf with other spares I will probably never need.
Yes, that is the problem. My coach (small block Cummins) needs the valve...your coach (big block Cummins) doesn't need the valve. Seems every engine/air compressor/air dryer combo is different. That's why I'm not sure about the OP's 6V92. Might need it - might not.
Chuck as always thanks for your quick response. I followed many your posts for my fixes.
Yes my engine is 6V92.
I don't think I saw any kind of check valves connected to the dryer. The dryer is installed in a really hard to reach area. I might overlook it. Will try to take better pictures later.
The second wire is a ground . I just went to the frame and yes it is a pain to do it by yourself.and my new plug came with the new unit.
Hey Andy! What about the isolation valve? Did your coach have one attached to the old AD-4, or did you add one along with the upgrade to AD-9?
Chuck sure what that valve does, mine just came out of the box and I installed it. Not sure if there is one unless in internal?
Google KN23500. If your old AD-4 dryer had one, you would remember swapping it over to the new AD-9.
See photo of my last AD-9 dryer before installation.
Thanks, nope mine didn't have one😁
Thanks for the info.
I will connect the wire to the nearest bolt to frame.
I am at total lost on the modification now.
I went under the coach. I think the air hose connection is different between ad4 and ad9
I am at loss now. Wish I bought the ad4 reman instead of ad9.
But it has been so long it past the return window from Napa.
Should I continue the effort to change to ad9
Or
take the loss, buy another ad4?
Thanks
Personally I would get fittings to fit the newer drier. They make adaptors for just about anything.
Without seeing exactly what you are seeing, it is hard for us to offer specific advice. I am almost sure we have had Forum members upgrade from AD4 to AD9 without any great difficulty. As I recall, the only hassle was some minor mods required to the mounting bracket and the wiring for the exhaust valve heating element. Neither should present any great challenge.
Like craneman says, if your concern is that the hoses don't line up exactly, that can be fixed by rerouting the hoses slightly, or with adapters.
Both dryer models should have the same three ports: supply, delivery and control. Two big hoses - one small hose. Hose size should be the same for both models.
Note: The photo of my AD-9 (Reply #9 above) shows the "isolation valve". Based on what Andy said (Reply #10) your U300 model coach will not have that part. Disregard it.
The data sheets linked below illustrate the physical difference between the two dryer model connection port locations:
https://www.anythingtruck.com/instructions/060-AD9ServiceDataSheet.pdf
BENDIX AD-4 AIR DRYER Manual (Page 7 of 24) | ManualsLib (https://www.manualslib.com/manual/392579/Bendix-Ad-4-Air-Dryer.html?page=7#manual)
Now you're in a good place to be and you don't realize it yet. When you're at a loss, you have room to learn.
As Chuck & Jeannie wrote "Both dryer models should have the same three ports: supply, delivery and control. Two big hoses - one small hose." So connect the little hose first. The look at the two big hoses and decide which one is coming from the compressor and which one goes to the wet tank. If they don't reach go to the truck hose store and have new ones made. My local NAPA is not a "truck" NAPA but I'm in the middle of commercial farm land so yeah, they got that.
Art Joly
Mine didn't either...
see ya
ken
Several years ago, I replaced our dryer with a spin on Meritor/Wabco type dryer. It's made next door in Poland but the quality is excellent and it only take a couple of minutes or so to remove and replace the spin-on with a spare. For $59 delivered plus tax, it makes changing easy. It only took one or two $8 fittings and a different mounting bracket. Air Dryer Assembly R955205 Replaces Meritor Wabco System Saver 1200 Series |... (https://www.ebay.com/itm/153044554423?_trkparms=ispr%3D1&hash=item23a22a92b7:g:B6AAAOSwtoVbMG2~&amdata=enc%3AAQAGAAACkPYe5NmHp%252B2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsStEKTPzZMfQmny3knR97t0H197h3plAebbQGKGB7bw1pN61k7q1xZ%252BjQb5u%252F02oA4nXeOSR2jxeHumzWTkQwpyfJtjwyHkybO71FhyEWQ7ghf8ioiTnQOSH8GCf8OYGho9KQ07CcEpmOnljh90j%252FBC%252FhjVuz1hT%252BeNQapfriOHIhRrKJpFnGURnGcmYEetP0l3dBSif8hzljFV23dcJTHEPOD2oOmnSPKpqncqtCO5vTeK2I%252FJZ1orFCZtCw6EDvEcXjudIhqeSetf7qXdeg4%252BHb4J3bxPC2%252BiGogf1xAcao7qWz3UXfR4Y%252FUFtl2DwWGuQ5E7oLnuXL21joIkFi%252FLpoHI8b0RVHvkLtvTUxysdkKzG6ceX3sKsgGbvSO7JrG%252Fpj%252FkwyxLcykznApOeAgLAtAhYLt2EbSblT8BJU4vd4my%252BVh3d6n7ftRYD3x7j%252FAbTiDlXQEx0sw61xiHBbmc8nJ88TmVB1UeK6v%252B9s%252F1UeCx9dQVQCIbSYorkzCf%252BwPXCLx5ohZeiyj0nBnYBalvjmXRsiCQI5JZgjzeKDJkxC8DF8Gc0hM9%252BtclcFchSXhO%252BE2pBJ%252FjiV4jP7gEbvuQDknoT1V5HQZPRb7uJcoO8Rr9OFyNajGRzQ8k9cSK31CEEFgoTQBCVglXcm1ix6KcSu5e0V2gaWVJmFmTdFOY2YkKLlDACZjDWNM5h%252FUtrexAfAONuEzyK00yFPFOrZw8m5oRq7hteAUboYoQsHV85EP8H4wX6CDnWj52jrghDjacA%252BT7n66Fw30lbRhL5Zxd4TAyaQzGqAnXWfO%252Fk1RuOuXrDBySjhOPbzUuofv1JmG%7Campid%3APL_CLK%7Cclp%3A2334524)
Pierce
Thanks you All, I am going to spend the time to do the conversion from AD4 to AD9
Wish I leaned Wabco mentioned by @Pierce & Gaylie Stewart early. may be next time when the air dryer needs to be serviced.
In case you decide to make the change, here are photos of the parts needed. I can't remember if I used the single 90 in the photo.
Diffferent Foretravel models may require alternate fittings.
And it's Wabco not Webco as I spelled it.
Pierce
My father, bless his heart and may he rest in peace, drilled into me that "we do not keep adding pipe fittings until it fits!"
I don't need to be the smartest person in the room, I just need to be smart enough to find the person with the answer.
In this case, when I do my air dryer* IF I have a prblem with an air hose I'll take it to my local NAPA dealer and say "Please make me a new air hose this long that fits "this." My air hoses are coming up on 30 years old . . .
*On Memorial Day duke the Dog snatched me off my feet in pursuit of a cat. I broke the fall with my face on the edge of a 12V battery sitting on the ground. Duke the Dog is suitably contrite, and tomorrow's work on the fuel bay door is postponed due to my needing to see the eye doctor (ophthalmologist) to have an expensive Q-Tip shoved in my eye.
That's my latest excuse.
I would not dream of using pipe fittings. The fittings you see above are AN fittings. AN for Army/Navy. They release in a tiny fraction of a turn and then only a couple of fingers are needed to take them off as they spin really easily. For a primer on fittings with many terms explained, visit A Detailed Guide and How-To for AN Hoses, Fittings, and Adapters (https://www.havocspeed.com/havoc-speeds-guide-to-an-hose-fittings/) Terms like JIC are among a list of commonly used abbreviations.
Pierce
Finally spend the time to change the air dryer from Bendix AD4 to AD9. It is basically drop in replacement. The same mounting hardware can be reused. Has to change the wire a little bit. AD4 just have one wire, AD9 has two wire. I connected one to the old AD4 wire, then connect the other wire to the nearby frame ground. The fittings are seized on the old AD4, luckily I have the extra fitting ready so I can use the new fittings instead of getting the old fitting off.
(https://www.foreforums.com/MGalleryItem.php?id=4906)
(https://www.foreforums.com/MGalleryItem.php?id=4905)
(https://www.foreforums.com/MGalleryItem.php?id=4904)
(https://www.foreforums.com/MGalleryItem.php?id=4903)
The task is not easy at all, it took me about 4 hours to complete the change. I initially tried to get the dryer off by loosing the two ring holding bolt. That was impossible. There is not place to put wrench on. I then decided to took the whole mounting hardware off. That is a little bit easier. Still not easy since you can't see the bolt and have to get the socket one by feeling. Ad as somebody pointed out already, the position of the dryer is very awkward. It collected all the dirt by the rear tires. It is very hard to do anything in the cramped space. The engineer who place the dryer in that position should be assigned to change 10 dryers 8)
Thing will never go smooth, once I reconnect all the hose and wire. Engine start, I can see the air pressure is rising, great. At least I didn't connect the supply hose to the delivery port. :D But WTF, it is over 140PSI and keep rising. Didn't hear the purge valve kicked in. Old AD4 purge normally at 120 psi. The D2 governor might be seized. Of cause it is going to seize after 5 hours of sweat to change the dryer.
Reminds the first time I changed the D2 governor one and half year ago with the encouragement from
@stump. I know nothing about the air system back then, now I know a little and I am not panic anymore.
The plan is to buy a new D2 governor with cut in pressure at 110 psi. I think @Chuck & Jeannie recommended adding gauge to the d2 governor. Bought few gauges and plan to add after the d2 governor.
I hope it is the D2 governor issue, but the current one is only about a year old. Will report back
When you buy the new D2 governor, get a spare to keep in your "parts" drawer on the coach. Nice to have when you need it, which is usually when you are in the middle of nowhere on a holiday weekend when the stores are closed.
110 PSI cut-in would be a little high. I would shoot for cut-in at around 90-100 and cut-out at 120-130. There is
supposed to be a "fixed" pressure range of 20 PSI between cut-in and cut-out. I have found it is often more like a 30 PSI range. As long as the D2 you buy is adjustable (removable black cap), you can always tweak the settings after installation.
Yes - a pressure gauge connected to the D2 is very handy. Lets you monitor the wet tank pressure for trouble shooting, and is useful when adjusting the D2 governor. I ran a short braided air line from the unused RES port on the D2 up to a gauge mounting point that was easily viewable from my engine access hatch. See link below:
Dash Air gauge has two indicators. one white, one red.. ??? (https://www.foreforums.com/index.php?topic=24878.msg195836#msg195836)
Source for the braided air line I used:
JEGS 41057: Mechanical Gauge Hose Kit -4 AN Braided Stainless Steel Hose [3... (https://www.jegs.com/i/JEGS/555/41057/10002/-1)
The only thing I can think is the d2 governor.
What else could cause air compressor not unloading?
Air dryer shouldn't be the issue.
Could it be the unload valve inside the air compressor?
No question, the governor is the "most likely suspect" and is the least expensive and easiest to replace.
Kind of like changing fuel filters if performance issue-- most likely suspect.
I removed and re-installed the band clamps. More of my extensive but useless skill set: i.e. working blind.
Just replaced with a new D2 governor and still no purge from the air dryer and air pressure still get to 150 psi and not stopping
I am at lost now. What could be the cause?
I plan to change back to the old AD4 dryer and see if it is still like this. any other suggestions?
Possible unloader valve stuck in the compressor. Put some corrosion X in the port from the tank to the compressor.
Went through the same trouble when my 4 would not purge, thought what heck I will change over to a AD 9. Went through the same thing u did with mounting , got back together and bingo no purge, made a few phone calls no help.
Sooo starting looking around the compressor and found between the head and bracket on the side of the compressor was an open port put a 1/4 inch plug on and bingo worked.
Long story short after rebuilding my 4 and no purge bought a 9 and all along it was a missing plug. Good luck. Call me of I can help 406-852-3776.
Thanks for the info.
Your engine is also 6V92, I hope the compressor is the same model.
I am trying to picture where the port is located. When you say between the head and brackets, are referring to between the compressor head and the d2 governor gasket? I don't think there is any open port there.
Has to be somewhere else.
I had the same problem 6 years ago when I was servicing the air system (with inspiration from Chuck!) and rebuilding the AD-4. I found out after all that work it wouldn't stop building air even with the dryer bypass and a new governor. I also tried using a shop compressor with 100 psi hooked up to the inlet port on the compressor from the the governor to check for leaks. After getting tech support from Bendix I finally figured out the unloader valves were rusted shut from neglect by the PO.
Unfortunately this was a Tu-Flo 501 compressor and to service the unloaders you have to take the head off! The newer models allow you to access the unloaders from the top. As Craneman suggested I tried removing the intake hose from the engine and spraying the unloaders with PB Blaster to free them up but with no success.
It's a royal pita to access the unloader port on a 6v92 with a Tu-Flo 501. Because the compressor is on an angle in back of the engine the unloader port faces downward and I had to get on top of the engine and hang upside down using a mirror to see what I was doing. There is very little room to work. It was in July and heatstroke weather here. After many attempts, a few new cuss words and struggling mightily, finally got the old ones out and replaced with new ones. You can get the unloader kit and Tu-Flo field service kit online or at your local big truck parts store.
If you are going to do this, make sure you soak the head bolts well or you might snap one off. Also make sure you torque the head bolts down to specs when done. If I knew what I was in for I would replace the 501 with a newer model. Easier access to the unloaders and more cfm.
This link should give you all you need to know with some pics. Good luck!
PS: Don't overlook periodic maintenance on the unloaders!
Jerry
Air Leak (https://www.foreforums.com/index.php?topic=28212.msg246145#msg246145)
Thanks for the post. The step in your post sounds very scary.
I have talked with Andy and I will try his method first.
If that is not working, I might have to follow your step. I don't know if that is even doable for me.
Is there a drop-in replacement of the air compressor?
How easy is it to replace the whole air compressor than just service the part of it? I can't image hanging upside down for many hours to work on this.
I checked with Foretravel service and was told that the Tu-Flo 550 or 750 should bolt right on as long as it is one for a Detroit 6v92.
If I were replacing mine I would get a reman 750. Either way it's no easy job. The intake and output ports should be in the same place as well as the cooling hose connections. I would get some plugs for the coolant hoses to minimize coolant loss. I lost about a gallon or so when I disconnected mine. Either way it won't be easy because of the cramped compartment and the weight of the compressor.
An upgrade from a 501(12cfm) to a 550(13.2cfm) or 750(16.5cfm should give you much more cfm and be much easier to service the unloaders. I would however double check with Bendix or somebody that made the upgrade to make sure either one will bolt on to a 6v92 with no modifications.
I like Andy's solution better!
Jerry
It is fixed now! :D
Short version:
Changed to a known good D2 governor and everything is working.
Long version:
So I was trying to fix the issue of AD9 not purging and air pressure keep rising over 140 PSI.
The compressor model no. is Bendix TU-FLOW 501
I tried
@Andy 2 post. I couldn't find the any missing nut on the opposite side of the D2 governor right below the alternator. Apparently D2 governor can be installed on both side of the compressor. This side has a nut to fill the hole and it seems just fine.
I really not want to go through what
@coastprt suggested. Losing 2 gallon of the coolant, taking the head off. Just too much for my wrenching capability. I want to rule out other possibility before going this road.
First I followed what @Chuck & Jeannie suggested, adding a pressure gauge to one of the port of the Reservoir (1/8 pipe thread). The gauge is showing around 75 PSI when front gauge shows about 120 PSI. That is certainly not right. Without enough pressure, D2 governor won't work. So I took the fitting off the governor and directly connect the gauge to the hose from the reservoir. and I still got about 75 PSI. So the issue is between the hose to the wet tank. Looking into the fitting, I can see there are some rust are blocking the hose. While under pressure, I used a small needle to clean up the hose and decent amount of the rust was blown out. But the pressure gauge was still showing 75 PSI even if the front gauge shows 120PSI. There has to be something down the hose.
So went under the bus to check the wet tank. There is a Tee fitting which connects the hose to governor and a safety valve (Bendix 284142 1/4 NPT). I was trying to take the Tee off the tank, but it was seized really bad. and the male brass fitting was broken into half. It was a major challenge to get the broken fitting out. Luckily, I have this tool
(https://m.media-amazon.com/images/I/81dlMIaCOLL._AC_SL1500_.jpg)
With the help of certain words, I was able to get the broken piece out.
Connecting the safety valve to portable air compressor, it is leaking pretty bad. Connecting to the pressure gauge and 75 PSI even if the tank has over 100 PSI. So that might be the issue! I was super excited and quickly installed everything back, Only to learn that the issue is still there. But the good news is that the pressure gauge shows over 100 PSI now instead of just 75 PSI. Also I know for sure the Air dryer is working fine by directly applying 100PSI pressure to the control line to the dryer. good news.
I bought two D2 governor, one is Torque air governor (https://www.amazon.com/gp/product/B00T8JS0EM), the other one is Bendix OR275491X (https://www.amazon.com/gp/product/B0045V6U4A) Torque air arrives earlier than the Bendix, so I replaced the one I bough 1 year ago from Napa with the Torque air. I never thought the D2 governor is the cause of the issue. Old one is only 1 year old, new one just bought. But none of these two governor works.
(https://db73q1dut0rlp.cloudfront.net/eyJ3aWR0aCI6ODAwLCJoZWlnaHQiOjYwMCwiZml0IjoiY29udGFpbiIsIndhdGVybWFya2VkIjp0cnVlLCJrZXkiOiJhc3NldHMvaW1hZ2VzLzg1OTIzMzgvbGFyZ2UvYTk0M2Y0ZTFjYTE4YmMxMzJlZmM2MmU4MDY5YzQxNWIuanBnIiwidmVyc2lvbiI6Mn0=.jpg?s=1fe9b92f98f4a9fcdb68f0022f00c89e8f6c20aac801b006728306e78b8ac3b8)
Without knowing exactly how the D2 governor works, I applied 120 PSI air to the reservoir port. I can see the piston moving, but no pressure from the unloader valve. I initially thought it is normal. as the two governor tested the same. How likely 1 year old governor and new governor both failed at the same time? Well, I am the lucky one. Recently I received the Bendix Reman governor and I apply pressure to the reservoir port, there is air come out the unloader/control port. And now everything make sense. The D2 governor is so simple. When reservior reach over 120 PSI, the piston will move and deliver the air pressure to the control/unloader port. The air pressure will then trigger the air dryer purge and compressor unload. Install the new Bendix governor, and I finally heard the purging sound. It never sounds so good! Air pressure also never exceed 120PSI. All works now!
So the moral of the story is to use name brand part. Had the Bendix governor arrives earlier than the Torque air, I probably won't need to go through all this hassle. Well lesson learned. next time will just buy parts from name brand.
Congrats on persevering until you found the solution!
It sounds like your wet tank is producing a lot of rust particles that are finding their way into the tank fittings and air hose going to the D2. Although you have cleaned then out for now, it is very likely this problem will reoccur at some point, depending on how much you use your coach. IIWY, I would look into replacing the wet tank. A new tank with all new fittings and a new air hose to D2 might save you a lot of aggravation and down time in the future. Just something to consider...
I am thinking about replacing the wet tank. It has a rust pin hole at the bottom. That was my very first challenge to rescue the bus. With
@stump help, I am able to taper a new hole. According to the shop, it is illegal to patch air tank for over the road truck. So I always want to replace it.
What shop can repair the wet tank? I search air tank repair, nothing looks like a repair shop.
How much would it cost?
Use the Forum search tool. Search for "replacement wet tank". The top hit is a link to thread started by Len.barron where the subject is discussed.
I bought Mark Duckworth's wet tank on the Forum. He had an issue with desiccant in the tanks due to a failed air dryer canister and he bought new ones. No rust and I was able to get the powder out and it sits on my spares shelf should I need it.
I am embarrassed. I can't find the post using the search tool. I search for "replacement wet tank". Only one post returns and it is my own post O:)
(https://www.foreforums.com/MGalleryItem.php?id=4909)
Can you provide the direct link to the post?
OK - I was in town earlier using my phone. I'm back on my computer now where I can post a link. Read from Reply #12 on down:
Basement Floor Bulkhead Repair Aluminum (https://www.foreforums.com/index.php?topic=43679.msg440101#msg440101)