I am having a strange situation with the A/C on my truck. 2 yrs ago you could just about make ice cubes when the A/C was running. Earlier this summer it could at best be described as fairly cool when it was running. I assumed it was low on refrigerant so I added some Duracool. Since I added the refrigerant I noticed it would at best be described as slightly cool. I checked the refrigerant pressure and I had overcharged it a bit. I removed some coolant and it is now right in the proper pressure range. However it is still only cooling slightly. Of course everyone is going to say I have leaves and gunk built up on the evaporator but I think there is something else going on. The compressor is running in REALLY short cycles. With the engine at idle it compresses for 2 seconds and then stops for 8 seconds. Does anyone have any idea what could be causing the really short charge cycles?

The low side pressure is about 30psi when not compressing and it drops down a bunch when compressor is running. It is also 30psi across the board when truck is turned off.

Any thoughts?

 

I shouldd use search before I just post. Based on the thread below it sounds like I am still low on coolant. I really need to get my hands on a good set of A/C manifold gauges. I have been trying to find a set for over a month. I guess I will check and see if any of my friends have proper manifold gauges I can borrow until I can buy a set of my own.

Here is the thread I was referring to above.

https://www.dieseltruckresource.com/...rt+a%2Fc+cycle

 

If the condenser is extremely hot then your Viscous fan clutch may not be pulling enough cooling air across the condenser. Try cooling down condenser with a garden hose if the ac cools better then you may need a Viscous fan clutch. If you have contaminated dryer you could have moister in the system causing internal ice to form and block refrigerant flow. . If you notice any frost forming on the high side then you could have a restriction, Orifice tube could also be plugged. Also blend door can be stuck or not operating properly.

 

A/C is fixed. I found a neighbor with manifold gauges AND read the FSM. Super short compressing cycle is top symptom in troubleshooting section of FSM. Either faulty low pressure switch or low refrigerant. In my case I was low on refrigerant. A can and a half of Duracool and the A/C is awesome again. After letting the engine run for 5 mins I took the gauges back to the guy I borrowed them from. Ambient airtemp outside the truck is 79F. The air coming out of the vent with A/C on max is 42F. That is right inline with proper performance specs in the FSM.

My lesson here, use the search feature on here AND read your FSM and most things can be solved. Oh yeah, and get a proper set of manifold gauges so I can tell what is truly happening inside the system.