No air pressure in secondary tank

Is it a Columbia? I believe your wet tank is actually a split tank making it a wet tank/secondary tank and there's an internal check valve that's stopped up.

 

Check this out, that should fix your problem. Hope you get this before you go to the international dealer. I work down the street from them and have never had luck getting good service there.

 

The ac problem is a direct result of the low air problem.
My 07 Columbia doesn't have any ac till both air tanks are full.

 

Yep, the Columbia's HVAC control unit wont send the signal to the a/c compressor to turn on unless the truck has secondary air pressure.

 

Hm learn something new every day.

I was under the impression with the exception of the auto trans the engineers systematically removed air driven appliances such as wipers etc from the cab.

 

@lepton i had the same thing happen on my freightliner a few years ago. Turns out that primary tank had a solid baffle with a check valve in it. I plumbed around it temporarily till i could get the check valve.

And you're ac won't kick in if you don't have air in the secondary tank. My columbia actually had 3 tanks. 1 the wet tank, the internal dry tank on the other side of that check valve, and a second full size dry tank.
None of the other things like the splitter, seat, suspension are supplied air if that check valve gunks up.

 

Fyi, you could change that check valve in ten minutes if you got the right thin walled socket and a 12 inch extension. Or plumb around it in an hour if you have access to a place you can buy fittings and air line.

 

Off topic - I have the $159/hr. beat.
I had a code going across 80 heading west to SLC. Guy on the phone tells me I was derated 5% and I had like 5 hours until I derate to 50%. So I hammer down, ice & snow be ######, get to Ft. Bridger where a Volvo Mechanic has the software to work on it.
Girl in the office says, with heavy northern Norwiegan accent, " It will be 5 O'clock before he can see your truck. This means we will have to go to the overtime rate. The overtime rate is $187.50/hr. You are ok with dis?"
So I go out to drop the trailer, and I guess 5 hours of hammertime cleared whatever it was, cause code was gone. They can stick " The Overtime Rate " in their ###. And problem never came back. I think something was just wtf cold.