[WSallai]

Hello, Friends.

Before I purchased Coach #416, the Thomas 120VAC Air Compressor was replaced by a previous owner with a Lowe’s Kobalt brand air-compressor.  It made all kinds of racket like you would expect it to when it ran.  I removed it and have regretted it since as I did not have a replacement on hand.  I do not know what model Thomas was in there originally and how it was plumbed or wired next to the 20kW Kohler Generator.

The 120V Air Compressor is used to level the coach using the air bags controlled with the HWH Computerized Leveling Controller.  The main engine-driven air compressor does the duties of filling the air bags when rolling down the road.

I would appreciate information provided from anyone who replaced their 120VAC air compressor with the Thomas or an equal or better compressor.  Photos of their current or new air compressor arrangement showing plumbing & wiring would be fabulous.

Question: If boondocking, would not a 12VDC air compressor be preferred to a 120VAC air compressor to keep the coach level when parked?

[encantotom]

hi bill,

if you do a search under air systems you will find entire threads about your very question. alot of us have replaced that compressor.

the 12v compressor on mine is a thomas as well. the 12v system will do all your basics....air doors, sewer valves, toilets.

i just got done living in ours for almost 7 months and i used the 120v compressor. i found a new old stock one on ebay that is a jun aire.

there are lower priced good alternatives too you will see in the threads here.

if you are boondocking, and have no 120v shore power, then yes, the 12v is preferrable.

tom

[rheavn]

Question: If boondocking, would not a 12VDC air compressor be preferred to a 120VAC air compressor to keep the coach level when parked?

The 12V compressor does not provide air to your coach's leveling system.  As Tom said the 12V compressor only supplies the slide seals (if any), the pocket doors and toilets.  On my coach, the sewer valves are not supplied by the 12V compressor.

When I boondock I prefer to run only the 12V compressor at night, but during the day I run the 120V compressor off the inverter and recharge the batteries with the generator.

As Newell added more slides the little 12V compressor couldn't even keep all the basics supplied with enough air and it was replaced with a second 120V compressor.

My coach has a Jun-Air, model 600, 120V compressor. I believe that Newell now uses Thomas 120V compressors exclusively.

My 12V compressor is located in basement compartment R-1. I would find someone with a coach that has the 120V compressor mounted in the generator compartment to see how it is wired & plumbed.

[Richard]

To add a few more bits to the excellent info Tom and Steve have provided.

I have a Jun Air pump also. I have had Thomas and Gast pumps. You cannot hear or feel the Jun Air run. They can be pricey, but homeboy didn’t like the compressor cycling to wake him up at night.


One, whatever compressor you choose, it must have a check valve to prevent the system pressure from feeding back into the compressor, and it must have a pressure relief at the end of the cycle to release the pressure on the compressor so that the compressor does not start against a high head pressure.

You will probably find in the compartment with the generator blower the classic well pump switch. The compressor is turned on and off by that switch. You will also find a second box wired in with the well pump switch with an electrical relay. That box is controlled by the HWH leveling system. The HWH leveling system turns on the compressor whenever the HWH system calls for air. Be aware that the HWH activated relay BYPASSES the well pump switch, and therefore the compressor will generate pressure up to it’s max rating. Which is 150 psi for a Thomas compressor. There should be a Norgren pressure relief valve somewhere around the pneumatic piping close by those two switches to prevent you from overpressuring the air bags.

I personally do not like, detest, hate, strongly advise against, and generally despise leaving the coach in the auto level mode. I do not like the algorithm that HWH uses. It will lower, lower, lower until one of the low pressure switches in the manifold tell it to stop. Then it raise until it maxes out, then it starts lowering again. Because the low pressure switches in the six pack manifolds are usually disconnected, the auto level algorithm can really put the coach in a twist. Plus I don’t like sleeping in a roller coaster.

If the coach won’t stay reasonably level for a couple of days, then there is an air leak in one of the air bags or it’s supply. That should be looked after.

Of course my diatribe about the HWH autolevel feature is purely my opinion, and others feel very differently about it.

[HoosierDaddy]

What is the CFm requirements we should look for in a 12 volt and 120 volt air compressors?