I've been piecing together an air horn system for my RV for the last couple years now. I've pretty much got everything except the compressor. Viair has been recommended to me as a brand, but of course with quality comes a price. I found this eBay auction, seller is unloading dozens of Viair 275C compressors for $75 OBO + shipping that his company isn't using anymore.

I'm leaning that way but it's still on the high end of my budget, so if anyone has a better source for 12v air compressors (or happens to have one sitting around not being used) let me know!

I cannot speak on that particular Viar compressor, but many of their products are generic Chinese with a higher price. We 4WD a lot in the desert here in CA and AZ, and we all air down a lot for soft sand, and have to air up again for hard surfaces and higher speeds, so we see a lot. The Viars have about the same duty cycle limitations and failure rates as the other, cheaper Chinese compressors. I think the MV50 generic type is the best buy, but quality and longevity are as variable as the others. It just moves the most air for the dollar (at least until it fails). Short-cycling it helps. I have added a small fan to one of my little pumps, and it has topped of my Barth tires (8) and bags (4) for 10 years without ever stopping for heat reasons.

When I see a duty cycle expressed in percentage only, a red flag appears. The user needs to know how long in minutes to run it before shutting it off.

If you have a tank, a small compressor would do the job. With an auto pressure switch, the duty cycle would not be a problem. For my tag bags, I use a little Edison compressor with an automatic pressure switch that would also keep an air tank pressurized. Consider a larger rather than smaller tank, as compressed air is handy for a lot of things. Like blowing desert dust off a curly dog. Really cleans the patio rug, too. We were in cockleburr hell last weekend. Coulda used a larger tank, ourselves.

Air horns used to use a vacuum-driven pump that were very reliable. They are still available on eBay and auto swap meets. The original Barth air pump is not too bad, either.

Another consideration, if you have a little room underneath is a small 120 volt compressor with a tank. That way, whenever you run the genset or are plugged in, the tank will fill to the compressor cut off setting and will be good for quite a number of blasts on the air horns.

quote:

Originally posted by bill h:
I cannot speak on that particular Viar compressor, but most of their products are generic Chinese with a higher price.

Really! Well that's certainly news. The 275C I mentioned is advertised on Viair's site as a 25% duty cycle. From another area where they sell entire kits for onboard air supplies (which is what I'm attempting to build), it looks like that translates into 10 minutes run time and 30 minutes cooling.

The tank I have is an old Ford model (I have no idea what it came off of) and I believe it's 2.5 - 3 gallon or so. I bought it used WITH a compressor, but that compressor gave out a short while into the "test" phase. It wouldn't fill the tank beyond 30psi or so and then crapped out completely. I could get it rebuilt for around $40 but I'm sure it has a pretty weak duty cycle, and it seems just as smart to buy new with this particular component.

A quick Google on "MV50" bring up several manufacturers, including Q Industries, Russell, and Super Flow... are those all the same? Should I be choosing one over the other?

Thanks for the info thus far! I was hoping someone here would have some considerable experience with vehicle air supplies.

quote:

Originally posted by scottydl:

A quick Google on "MV50" bring up several manufacturers, including Q Industries, Russell, and Super Flow... are those all the same?

Who knows? A brand name means very little today. Most companies exist only to stick the decal on the product and market it. It changes from day to day. There is a lot of legal copying (outsourcing) and a lot of illegal copying (counterfeiting) going on over there. I am told even the people involved can't keep track of it.

Check Harbor Freight, too. Some of their compressors look very much like other brands.

quote:

Should I be choosing one over the other?

Hard question, too. I had someone very upset with me because the compressor I recommended failed and let them down. With poor or non-existent quality control and the factors mentioned above, no recommendation would be any good, anyway. As in, "All marriages performed by the Captain of this ship are good for the duration of the voyage only."....Or the standard Army parachute guarantee. "If it doesn't work, bring it back."

I do know the bigger the pump and the shorter its duty cycle and the lower its peak pressure, the longer it will last.

There are a number of good tests and articles on the MV50 on the web, usually on 4WD sites. They are very good when they work.