Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 13, 2025 ...

450C Compressor | VIAIR Corporation
https://www.homedepot.com/p/Campbell-Hausfeld-Desiccant-Dryer-PA208503AV/100671461

If you have room, I installed these to air up coach and fill tires without running engine.

Jim, Interesting suggestion. Not sure about our available space. Will have to check out the dimensional specs.

Are you using this as a total replacement for the FT OEM aux compressor equipment?

Amazon link to the compressor Jim recommended:

Amazon.com: Viair 45040 450C Air Compressor Kit: Automotive

I don't get it, unless it's speed you're after to air-up above 85 psi. It requires the engine running, just like our onboard!

Been awhile getting back to the forum. To identify our aux air compressor required finding someone able to wriggle into the basement alongside the wheelchair lift. Very little space available.

Update on aux air compressor in our 02 U270. Neal Pillsbury correctly named our aux air system. From his earlier post:

" In model year 2002, FT started using the Thomas TA4101 12Vdc, 1/3 HP, 100 psig (max.), auxiliary air compressor.  I believe that is what you should find in your coach.  The reason they did this was due to the need for a higher duty rating and a more robust compressor when slides were added to the coaches."

Pictures attached. Yes we have the Thomas 4101. (even though we do not have any slides) The desiccant container is visible as are two water traps. Neal, is this the Wilkerson filtration system you mentioned?

Newbie question: Are there separate desiccants/filtration systems for the engine air compressor and the aux Thomas compressor?

Is the Thomas a good unit? Is it strong enough to air the suspension to travel mode without damaging itself, overheating etc. (I suspect the answer is no. Isn't the aux unit only designed for maintaining level and slide operation...True/False?) I might consider running it more often if there were no issues using the aux compressor to achieve travel mode and airing tires. It would be nice to avoid running the Cummins and disturbing our park neighbors. Could make our departure from campsites a bit quieter without any extra diesel exhaust as well.

A. "Newbie question: Are there separate desiccants/filtration systems for the engine air compressor and the aux Thomas compressor?"

Yes: They are distinct, separate systems.  The main (engine) air/braking system Haldex (Midland Grau) desiccant and coalescing filter tower is mounted on the engine frame.  The auxiliary Thomas compressor Wilkerson filtration and desiccant bowls are mounted at the aux. compressor.

B. The desiccant container is visible as are two water traps. "Neal, is this the Wilkerson filtration system you mentioned?"

Yes:  Your pictures show the Wilkerson System drying components; (2 dry bowls and the desiccant bowl) that are used to strip moisture from the Thomas TA4101 auxiliary air compressor exhaust stream.  While some readers may not understand or condone going to the extra effort of avoiding moisture in their air systems/tires, my experience in power plants has shown me the folly of not attending to that detail.  In an air system, one either attends to moisture-free air up front or one has to pay the price, in much more costly terms, down the road.

The nuisance of the Foretravel/Thomas TA4101 compressor/Wilkerson drying components auxiliary air system design is that the drying components are sized for and the design assumes a reasonably tight air system. The operation of the relief valve and automatic blowdown solenoid also often fail and thus detract from system reliability. The desiccant, while easy to change if the desiccant bowl is easily accessible, is expensive (but there are several threads on how to minimize that factor —  Desiccant option for the HWH system . So, with a minimally sized design, if you don't correct your air leaks, you soon exhaust exhaust the desiccant and the rest of the air system components start to suffer.

C. "Is the Thomas a good unit? Is it strong enough to air the suspension to travel mode without damaging itself, overheating etc."

Absolutely yes:  The 12 Vdc Thomas (and not mentioned in this thread before, Gast) brand units are industrial/commercial application standards for medium duty air systems.  They are rugged, durable, high (%) duty cycle, reliable standards.  They use high quality cast iron frames with excellent heat transfer and their designs employ long life components that are rated to last 6,000 hours before minor rebuild and 12,000 hours before major overhaul.  In a coach air system (that is kept reasonably tight and leak free), that is more than (2), 30 year coach lifetimes with a 2 minute auxiliary tank (replenishment) pump up once per day and a 15 minute pump up (of all coach air systems), EVERY day, before getting underway.  Minor and major rebuild kits are expensive, but they reflect the component quality level and are readily available.

Prevost conversions, that have much higher needs than FT's because of their pocket doors, gen sets on air suspensions, air flush toilets, higher pressure air bags, etc., use Thomas and Gast compressors.  When they need more volume, they step up to 2 cylinder Thomas and Gast compressors first and then to 115/240 VAC compressors next. 

There are other light to low/medium duty options, like the VIAIR units.  But what isn't being said about the VIAIR's is that they are primarily focused on marketing/cosmetics whereas Thomas' (and Gast's) are focused on robust longevity and durability.

The VAIR units are widely used in applications where mobility is of primary importance such as in off-roading tire re-inflations (slow, but a decent, mobile backup to the premium Power Tank (CO2) choice), where peak ceiling pressures are compatible with non adjustable hysteresis characteristics, or in hardwired applications where appearance is of paramount concern and longevity is of secondary importance such as in air horn add-ons, show cars with trick pneumatic suspensions and where the air compressors themselves are an intentional part of the visual "candy", etc.  The Thomas and Gast compressors are decidedly "Plain-Jane, Industrial" by comparison.

There are plenty of reasons for any of the options.  Just make sure that you stay focused on DRY, CLEAN AIR.  Speed of air-up, ceiling pressure, hysteresis (difference between compressor set and reset pressures), looks, and durability choices abound, but unfiltered, wet air should never be one of the choices.

HTH,
Neal

Thomas TA-4101 DC Specifications
Neal, think this is the problem with the Thomas for airing up the tires, unless your tires require less than 100 psi.
For the rare times I need to inflate my tires to 115 psi, I do not think the "low/medium duty" Viair is going to be a deal breaker for me. It is rated for continuous  duty. From a search of the forum, it appears the Thomas, even if rated for 6000 or 12000 hours, is not overly reliable, as there are many threads on this and other forums about their replacement.

Anyone ever check out the "California air tools" compressors,they are 110 volt.