Air compressor

I once had a car that wouldnt go into 4th gear untill it was warm. That was a factory thing.
That is the only thing I can think of !

LX

 

I've seen this on BA921 compressors when the valves coke up. A little more info, like what truck/engine/compressor my get you some more help. We can't see what you have, so we need things explained to us.

 

On an 07 it's probably a BA style single cylinder like this:
http://www.bendix.com/media/documents/products_1/compressorsgovernors_1/ba921servicedatasheet.pdf
On the top is a cap, with 2 screws holding it down, this is the unloader assembly. If you pull that off and find burnt coked up oil in there, it could be an issue. Sometimes cleaning it out the best you can an replacing the unloader kit will get it working good again, sometimes not. The reed valves are directly under that, but you cannot get to them unless you pull the compressor head. You'll need gaskets and have to drain the coolant to do that.

What I've seen happen is when it's cold, things are sticky, so it holds the reed valves open, then when it warms up, things will free up and they'll start working.

Before you go pulling anything apart, I'd pull the discharge line off the compressor and make sure that the air compressor is not pumping when cold. If you can hold your thumb over the hole and not have air push past, with no air pressure in the tanks, then the compressor is not pumping.

It could be something like the purge valve hung open in the air dryer not letting it build, so isolate your problem and get a direction to go in.