I have an '06 5.9. The fan blows good and strong but when I turn the AC on the compressor tries to start but won't. It kicks on for 1-2 secs then off for 1-2 secs then on, off, on, off. Then it just doesn't try anymore and stays off. Any thoughts, first step suggestions or the like? thanks.

 

Sounds to me that you are low on freon. If that doesn't fix it, the pressure switch could be going.

 

I thought it might be low on freon so I bought one of those little cans from the parts store that came with a gauge. The compressor has to be running for it to work. So I had someone turn the AC on so I could add the freon while the compressor cycled on and off quickly beforevit stopped. When I attached the can to the truck line it read over 100 psi and couldn't take freon as the pressure was too high. Probably because the compressor wouldn't engage or whatever the underlying problem is. More advice is greatly appreciated.

 

Hate to say it, but it is time to take it to a AC guy.

Without a good set of accurate gauges on both sides, you are weeing into the wind.

 

This happened to me last summer on my 03 one ton.Did you read the directions on the can? ( I usually read the directions while the glue dries.) But read the directions,those cans tell you what to do .It worked for me,and I'am not a mechanic,but I got cold air.GOOD LUCK with it and let us know what works.

 

The pressure should drops when compressor kicks in even for a couple of seconds.
If the pressure didn't drop then something wrong the hookup.

 

Just checking. Did you hook to the low side and not the high side?

 

On R134, sizes are physically different from high to low.

 

Just checking.

 

Check to ensure the compressor clutch is not shot. This ended up being my problem and a realatively easy repair. There is a thread on here somewhere that is very helpful and even provides part numbers and sources.

 

Did you ever figure this out ?