Symptoms of a bad air compressor
 

FLD120
Sometimes both my air gauges do creep up to 120 and sometimes it stayes around 70 for about 20 mins.This does not happen often but more like 20% of the times I crank up the truck.It is more often in the mornings(or after shuting off for a while) and the temperature outside is not a factor.
Could my compressore be going out or is it the dryer underneath the truck?What are the symptoms?There is no air leak that I hear.

Before spending the money on a compressor maybe just your governer is what the problem. I am not sure how you test it but I would try that first. I have had the governers go out but have never lost a compressor yet. If you don't know what it looks like it is that small round thing on the side of the compressor. About 2 inches across and about 5 inches long. There are usually two small air lines going to it and two bolts that hold it on the compressor. They aren't hard to change. Takes about 20 minutes. Hope this helps.

Re: Symptoms of a bad air compressor
 

it's not the dryers fault.

the air governor requires air pressure to stop the compressor from making air.

to test; ensure that the air compressor is in the loaded cycle. remove the compressor discharge line from the compressor, and then run the engine at 1500rpms for 45 secs while holding a piece of cardboard in front of the discharge fitting. if the cardboard becomes saturated with oil, the compressor is worn out.

I would just tell you to look for oil in the wet tank, but oil in the air system doesn't necassarily indicate a bad compressor.

try draining both your air tanks. see if they have a lot of water in them.