Air dryer purge 15 seconds finally resolved

[Jon_C]

All

For the last couple of weeks ive been troubleshooting why my air dryer purges about every 15 seconds. Ive read the threads on here and understand how it’s supposed to work, rebuilt the pure air plus dryer, installed both kits, new governor, still constant purging and compressor loading. I put a gauge on the wet tank and its not leaking down pressure, no leak in the control line from tank to governor to dryer. So im scratching my head trying to think what im missing.

Well i had googled the pure air plus troubleshooting guide and looked at images of the unit online and realized my unit gas a bunch of extra fittings and connections external to the dryer. So i decided to remove all these extras and see if that resolved the problem and IT DID!

I have attached pic of the extras both installed and removed. There is a spool valve in the large fitting and one of the lines connects the dryer outlet check valve back to the control line.thru a restriction. Its my theory there was a leak allowing the control line pressure to bleed down through the outlet check valve causing the purging.

I dont know why this was on my unit or its true purpose but im very glad to finally have everything wirking properly for the first time since I purchased the coach about 7 months ago.

If anybody knows Anything about the extras please let me know, could have been Freightliner or HR who installed.

And if your having purging issues you may want to do the same.

[walt2137]

What year is your HR?

[Jon_C]

1998

[peterdube]

Jon, I know your pain. My braided stainless steel control line had a pin hole in it caused by welding slag that dropped between the frame and the line when it was being built and it melted the plastic line within the stainless housing. That was a pleasant find.No more 15 sec. cycles!!!!!!!!!!!!!!!

[Jon_C]

Hopefully it was covered under warranty, im sure that was a tough one to find too.

[gofastnow]

Originally Posted by Jon_C

All

For the last couple of weeks ive been troubleshooting why my air dryer purges about every 15 seconds. Ive read the threads on here and understand how it’s supposed to work, rebuilt the pure air plus dryer, installed both kits, new governor, still constant purging and compressor loading. I put a gauge on the wet tank and its not leaking down pressure, no leak in the control line from tank to governor to dryer. So im scratching my head trying to think what im missing.

Well i had googled the pure air plus troubleshooting guide and looked at images of the unit online and realized my unit gas a bunch of extra fittings and connections external to the dryer. So i decided to remove all these extras and see if that resolved the problem and IT DID!

I have attached pic of the extras both installed and removed. There is a spool valve in the large fitting and one of the lines connects the dryer outlet check valve back to the control line.thru a restriction. Its my theory there was a leak allowing the control line pressure to bleed down through the outlet check valve causing the purging.

I dont know why this was on my unit or its true purpose but im very glad to finally have everything wirking properly for the first time since I purchased the coach about 7 months ago.

If anybody knows Anything about the extras please let me know, could have been Freightliner or HR who installed.

And if your having purging issues you may want to do the same.

I know this is an old posting but just wanted to comment on it to caution others who might be considering removal of valving as shown above.
Let me start by saying I'm not an expert on the subject of air systems, but I believe the extra valving is related to your MH due to possibly having a Holset type E compressor. If you do have a type E, it requires the external valving, or a dryer with integrated valving necessary to handle the type E correctly.

[96 Wideglide]

Yeah, I remember thinking the same while reading this thread.

It's rare for manufacturers to add parts that aren't included for a reason!

[Jon_C]

Could you please refer me to where you got this information? Ive had no issues at all but now you have me concerned. I apologize if you think im just trying to spread false information i can assure you i am not.

Why would persons who know the answer to my question in original post not comment till 6 months later? Sorry im still here and would like to know. Thank you.

[96 Wideglide]

Hopefully 'gofastnow' will come back and give you more information.

I have a Meritor Wabco air dryer.

[jakestarr]

Ben, didn't you replace your air dryer which resolved a purge problem for a while and then began to drain your tanks again?

[96 Wideglide]

I replaced my dryer, which solved the issue of the dryer releasing some air (even long after engine shut down).
My issue now is the new dryer allows some moisture into the wet tank !!

[jakestarr]

Ben, I also replaced my dryer with an oem because it was draining the air tanks. it resolved that issue for a while, but is draining the tanks again!!!! I don't have the moisture problem!! Does your new dryer stop the air tanks from draining?
Thanks, Jake

[96 Wideglide]

Yes, it did.

Are you sure it's your dryer thats draining your tanks? Can you hear it?

[jakestarr]

Ben, sorry for the dumb question, I see in your last post that you have no tank drain down after engine off for a long time!!!