Just thought I'd share my experience with Viair's warranty. I have two 400C compressors mounted to the outside of the frame rail on L brackets. Before I installed, I called Viair to double check that it was ok to mount under the truck and they said yes, it's a sealed unit and as long as the vent tube is routed to a dry location, it's fine. They won't be harmed if they get wet, just don't submerge them. Well, a while back I flipped them on and shortly after I heard a pop and one compressor went down. I called Viair and they gave me an RGA number and said send it back and they'll take care of me.
Earlier this week I finally get a call from them and they tore it down and it was full of water with a burned up motor and broken connecting rod. They said the fitting for the check valve had scratches on it and that they would not replace or repair it under warranty. I had a serious problem with this answer. How the hell are you supposed to tighten the fittings with a wrench and not scratch the cheap chrome plating? I escalated my call and finally talked with someone higher up that initially gave me the same answer. Then they started pointing to the fact that they were installed under the truck and that had to be why they got water in them. I had to remind them that I called and asked this very question and was given the green light. Yes, they have been splashed with water which I was told was acceptable, but they have never been submerged.
After standing my ground and reasoning with the guy, he finally agreed that he personally felt this was on them and should be fixed under warranty but would need to have some more people take a look first. They eventually called back and said they would be repairing and replacing parts at no cost to me. Turns out it was most likely a faulty check valve that allowed moisture to build up inside the unit and ultimately caused the problem. Apparently if you tighten the check valve fitting to the air line fitting with real tools and scratch the chrome plating, this renders the check valve useless.
Sounds to me like they need to upgrade to a higher quality check valve.
They still weren't 100% sure that this was the cause, but whatever. Since the other compressor is fine and moisture free, I have a hard time believing it was my installation. The air inlets are at the middle of the tank so it's not like the lines are at the bottom of the tank collecting all the water in the tank. I also periodically drain the tank and cycle the compressors to keep out all the moisture I can and I always get a very minimal amount of water vapor from the drain, never any pooling water.
At the end of the day I still won, but I don't feel I should have had to fight that hard. Anyways, just thought I would share my negative experience with Viair.