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Topic: Is the desiccant air dryer in line with the 12 v air compressor really needed? (Read 1875 times) previous topic - next topic

Is the desiccant air dryer in line with the 12 v air compressor really needed?

I am getting tired of servicing the small desiccant air dryer.  I noticed on a 2008 year (as I remember) coach that the only air dryer was the one with the electric driven dump valve.  So is the desiccant air dryer really needed?

The desiccant starts to turns pink immediately and is completely pink after about 6 uses of the compressor.  This seems silly.  Do others get to stay blue a little longer?

Also the dryer just before the desiccant dryer traps a lot of water - the dump value on mine appears to be stuck so the bowl filled with water after a week and I had to empty it by removing the bowl.  I'm going to Nac in a couple of weeks and get it fixed then.

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #1 –
We have the same question - the newer FTs (last year or so) we've seen do not have the desiccant bowl.

We and others have found cracking in the bowls of the system that allowed moisture in.  Our desiccant bowl was also quite corroded inside and we replaced it (both bowls, actually) in 2011 Photo upload - HWH aux compressor filter bowl replacement .  Based on that single data point ( ;D  ) the timing is about right for your 2004.

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #2 –
In fact I had to replace the whole unit about 2 years ago because the inside tube was so pitted and warn it actually broke off and the small screen at the end was clogged and the large screen at the top was so pitted it disintegrated when touched.    The screen on the new unit is just about clogged up.  I don't think this dryer has large enough capacity for the application.

Michelle, how do you remove the stone filter from the first in line dryer?  I see a pliers in the picture but I'm not sure what to turn.

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #3 –
Quote from: Michelle –
We have the same question - the newer FTs (last year or so) we've seen do not have the desiccant bowl.

We and others have found cracking in the bowls of the system that allowed moisture in.  Our desiccant bowl was also quite corroded inside and we replaced it (both bowls, actually) in 2011 Photo upload - HWH aux compressor filter bowl replacement .  Based on that single data point ( ;D  ) the timing is about right for your 2004.

When I had my new aux Compressor installed the Thomas Distributor in San Jose looked at my installation and commented that the descant bowl was not needed and makes the compressor work harder. Because of all the moisture and corrosion I saw I was'nt sure if that was good advise. So I am also still looking for a reliable answer before removing it.

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #4 –
Does the compressor in later rigs feed the wet tank directly?  If so, the dryer probably isn't needed (can drain the wet tank), but if it directly feeds the slide and air bag systems, I think collecting moisture there could be a major problem.  (...recent report of air bags filled with water and hydro-locking...)  Is there some self-purging dryer like the Haldex dryer for the service brakes that could be installed on the aux compressor?

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #5 –
This discussion prompts a further question.  The air pressure guages on the dash show an increase in pressure when the engine is running thanks to the engine driven compressor - and - they go up when the 12v compressor is running.  Without questioning that there might a difference, I had assumed that the air tanks are all connected and both compressors are independently doing the same thing.  Is this correct?

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #6 –
Quote from: Larry Rubin –
This discussion prompts a further question.  The air pressure guages on the dash show an increase in pressure when the engine is running thanks to the engine driven compressor - and - they go up when the 12v compressor is running.  Without questioning that there might a difference, I had assumed that the air tanks are all connected and both compressors are independently doing the same thing.  Is this correct?

Larry,

There should be a switch on the panel by the driver's left arm that says "Air Tank".  Flipping it on opens a NC solenoid valve that links the lines so the 12V compressor can help build pressure (so you can start airing up without running the big engine - being considerate of your campground neighbors). 

Leaving the switch off should keep the 2 lines isolated.  HOWEVER - if you see the A and B tanks go up with the switch off and only the 12V compressor running, there's a good possibility the solenoid valve is leaking through.  Ours did and we replaced it in 2011.

Michelle

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #7 –
Quote from: Larry Rubin –
Michelle, how do you remove the stone filter from the first in line dryer?  I see a pliers in the picture but I'm not sure what to turn.

Steve says the black flower-looking thing unscrews by hand (although he recalls there is an allen-head screw in its center if it's locked up and you can't turn it).

-M

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #8 –
Quote from: Michelle –


Leaving the switch off should keep the 2 lines isolated.  HOWEVER - if you see the A and B tanks go up with the switch off and only the 12V compressor running, there's a good possibility the solenoid valve is leaking through.  Ours did and we replaced it in 2011.

Michelle
Or the check valves on the air tanks are leaking which was in my case and why I had to replace them both below.

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #9 –
Some units have an auxiliary tank for the 12V air compressor and some do not. You can check this by looking at the schematic in the Foretravel manual.
For those units that have a switch that directs the 12V compressed air to the main air tanks you need an air dryer in the line in order to keep wet air out of the main air tanks, otherwise it highly possible for ice build up in the air lines especially in colder climates.

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #10 –
Quote
There should be a switch on the panel by the driver's left arm that says "Air Tank".  Flipping it on opens a NC solenoid valve that links the lines so the 12V compressor can help build pressure (so you can start airing up without running the big engine - being considerate of your campground neighbors). 

Leaving the switch off should keep the 2 lines isolated. 

I took at look at the Air Schematic (drawing B-2026 dated 3/24/03) to figure out what connects to what.  Much if not all of this is discussed in other posts but I wanted to put it all together.

Here's what I learned - please check and correct!  (some connections are left out)

The 12v compressor has 3 outputs: the wet tank, the slide out seal tank and via connections on the output of the right and left brake tanks, the air suspension.  I couldn't find the "Air Tank" switch and valve in the diagram as Michelle describes it but without the switch on, the 12v compressor feeds the slide out seal tank only as a normal occurrence. 

However there isn't any gauge to tell you when this tank is full and the seals are properly inflated.  You have to just trust that the compressor is working and keeping the slide seals inflated.  I understand now why some folks have to disconnect the fuse or the compressor connection manually to keep if from running.

The engine compressor feeds the wet tank only.

The wet tank feeds the right and left brake tanks.

The rear break right tank feeds the rear brakes (duh!), the rear height control valves (2), the air hose connection, and the rear suspension

The front break left tank feeds the front brakes, the front height control valve (1), the air horns and the front suspension

The 3 drains valves in front of the left front tire are for: the slide out seal tank, the front brake left tank and the right break rear tank.

The wet tank is drained via a valve in front of the left rear tire. 

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #11 –
Quote from: Larry Rubin –
I took at look at the Air Schematic (drawing B-2026 dated 3/24/03) to figure out what connects to what.  Much if not all of this is discussed in other posts but I wanted to put it all together.

The 12v compressor has 3 outputs: the wet tank, the slide out seal tank and via connections on the output of the right and left brake tanks, the air suspension.  I couldn't find the "Air Tank" switch and valve in the diagram as Michelle describes it but without the switch on, the 12v compressor feeds the slide out seal tank only as a normal occurrence. 
it is in the HWH manual schematic. See Attached. it is the rocker switch on top.

Quote
However there isn't any gauge to tell you when this tank is full and the seals are properly inflated.  You have to just trust that the compressor is working and keeping the slide seals inflated.  I understand now why some folks have to disconnect the fuse or the compressor connection manually to keep if from running.
Many of us have added gauges on the aux compressor line and the slide bladder lines for this purpose.



Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #12 –
Barry, did you keep the desiccant filter active? 

Mine is leaking around the o-ring and won't build pressure.  The screen above the dessicant is really corroded and should be replaced.  I put the bowl and the pink desiccant in a zip lock in the pickup and after being out in the Oklahoma sun there is a lot of moisture in the bag.  That moisture would have been in the system without the desiccant. 

I've not gone in search for parts.  Didn't see anything on the Grainger site like this filter.  Do I need to order parts from Nach or is someone likely to have it in Oklahoma City?

I'd like to get it back together without waiting on parts.

Thanks

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #13 –
Quote from: Johnstons –
Barry, did you keep the desiccant filter active? 

Mine is leaking around the o-ring and won't build pressure.  The screen above the dessicant is really corroded and should be replaced.  I put the bowl and the pink desiccant in a zip lock in the pickup and after being out in the Oklahoma sun there is a lot of moisture in the bag.  That moisture would have been in the system without the desiccant. 

I've not gone in search for parts.  Didn't see anything on the Grainger site like this filter.  Do I need to order parts from Nach or is someone likely to have it in Oklahoma City?

I'd like to get it back together without waiting on parts.

Thanks
I replaced mine from Grainger WILKERSON Dryer, Desiccant - Desiccant Dryers - 5Z610|X06-02-000 - Grainger

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #15 –
Barry,

How about a little info on why you chose that particular size dryer?  I was looking at a much larger one such as this:

http://www.nationaltoolwarehouse.com/15-SFCM-In-Line-Desiccant-Dryer-1-Quart-P138705.aspx

Am I missing some important detail that would make a larger one not work?

Thanks

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #16 –
:giggle:
Quote from: Jim McNeece –
Barry,

How about a little info on why you chose that particular size dryer?  I was looking at a much larger one such as this:

http://www.nationaltoolwarehouse.com/15-SFCM-In-Line-Desiccant-Dryer-1-Quart-P138705.aspx

Am I missing some important detail that would make a larger one not work.
Thanks
Because I had just enough desiccant to fill it :giggle:
It was because that was the same one that was in there. I never thought about getting a larger one.
 

Re: Is the desiccant air dryer in line with the 12 v air compressor really needed?

Reply #17 –
After learning so much from this forum since we bought our 2003 GV320 in February, I finally have something to contribute.

 I'm in the process of replacing just about everything around the 12V compressor and found the Wilkerson desiccant filter online at zorotools for $43.45 Desiccant Air Dryers by WILKERSON - Desiccant Dryers by Zoro Tools Industrial and a 3 pack of desiccant for $28.27 with free shipping Desiccant by WILKERSON - Replacement Desiccant For Dryers by Zoro Tools . Graingers price is $117.85 and $59.15. UPS just delivered and they look like the real deal. With the package of desiccant that came with the filter plus the 3 extras I bought I should be good for a few weeks :)

Also delivered were the Parker air filter from Amazon and the Haldex/Meritor check valve and HWH "Air Tank" solenoid from FOT.

I already replaced the Square D pressure switch and added a pressure gauge (thanks for that post, Barry). That pressure switch is available with an "OFF/Auto" lever built in. Very handy. I was able to eliminate the switch I had wired in the relay circuit.

Now to start installing...