How to update Bendix AD4 to AD9 on 91 GV U300

Topic: How to update Bendix AD4 to AD9 on 91 GV U300 (Read 2800 times) previous topic - next topic

How to update Bendix AD4 to AD9 on 91 GV U300

April 16, 2021, 11:47:23 pm

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

In @prfleming response @38,

Quote

Andy

I just had mine changed to the AD-9. Shop said they had to rewire the heater wiring for a 2 wire connection. Did you run into that? Mine was original I think - 25 years old. The labor on mine was $500.

Had to rewire the heater wiring for a 2 wire connection.
Then @wolfe10 mentioned few message below

Quote

The new generation pigtail has a separate PN from Bendix an

What is the part number?
I searched and found this 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

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #1 – April 17, 2021, 08:56:58 am

Quote from: Running Odometer – April 16, 2021, 11:47:23 pm

1. I searched and found this from find it parts. Is this the right part?

2. The old AD4 has just one wire. If I use this two wire, where can should I connect the other wire to? the frame?

3. Other than the wire, is there any fitting needed to update AD4 to AD9?

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

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.

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Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #2 – April 17, 2021, 10:39:10 am

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

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

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #3 – April 17, 2021, 11:31:31 am

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.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #4 – April 17, 2021, 11:39:52 am

Quote from: craneman – April 17, 2021, 11:31:31 am

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.

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.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #5 – April 17, 2021, 11:58:22 am

Quote from: Chuck & Jeannie – April 17, 2021, 11:39:52 am

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 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.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #6 – April 17, 2021, 12:07:18 pm

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.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #7 – April 17, 2021, 12:12:30 pm

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?

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #8 – April 17, 2021, 12:45:48 pm

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?

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #9 – April 17, 2021, 01:12:05 pm

Quote from: Andy 2 – April 17, 2021, 12:45:48 pm

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.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #10 – April 17, 2021, 02:24:10 pm

Thanks, nope mine didn't have one😁

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #11 – April 17, 2021, 04:38:16 pm

Quote from: Andy 2 – April 17, 2021, 12:07:18 pm

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.

Thanks for the info.

I will connect the wire to the nearest bolt to frame.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #12 – June 12, 2021, 09:36:28 pm

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

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #13 – June 13, 2021, 12:32:44 am

Personally I would get fittings to fit the newer drier. They make adaptors for just about anything.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #14 – June 13, 2021, 09:01:58 am

Quote from: Running Odometer – June 12, 2021, 09:36:28 pm

I went under the coach. I think the air hose connection is different between ad4 and ad9

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

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #15 – June 13, 2021, 12:45:21 pm

Quote from: Running Odometer – June 12, 2021, 09:36:28 pm

I am at loss now. Wish I bought the ad4 reman instead of ad9.

Thanks

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

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #16 – June 13, 2021, 08:45:24 pm

Quote from: Andy 2 – April 17, 2021, 02:24:10 pm

Thanks, nope mine didn't have one😁

Mine didn't either...

see ya
ken

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #17 – June 13, 2021, 10:05:32 pm

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 |...

Pierce

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #18 – June 14, 2021, 06:36:13 pm

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.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #19 – June 14, 2021, 07:15:37 pm

Quote from: Running Odometer – June 14, 2021, 06:36:13 pm

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

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #20 – June 14, 2021, 10:02:11 pm

Quote from: Running Odometer – June 14, 2021, 06:36:13 pm

Thanks you All, I am going to spend the time to do the conversion from AD4 to AD9

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.

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #21 – June 14, 2021, 11:53:55 pm

Quote from: Old Toolmaker – June 14, 2021, 10:02:11 pm

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 . . .

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 Terms like JIC are among a list of commonly used abbreviations.

Pierce

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #22 – April 08, 2022, 11:40:21 pm

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.

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

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.

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

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #23 – April 09, 2022, 08:59:17 am

Quote from: Running Odometer – April 08, 2022, 11:40:21 pm

The plan is to buy a new D2 governor with cut in pressure at 110 psi. I think Chuck recommended adding gauge to the d2 governor. Bought few gauges and plan to add after the d2 governor.

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..

Source for the braided air line I used:

JEGS 41057: Mechanical Gauge Hose Kit -4 AN Braided Stainless Steel Hose [3...

Re: How to update Bendix AD4 to AD9 on 91 GV U300

Reply #24 – April 09, 2022, 09:49:26 am

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?

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