Noise with ac on

[j.dehn]

I have started running the air in my truck and when the compressor comes on there is an anoying loud humming noise coming from the inside of the truck. I thought the system may have been low on oil so I drained and recharged the air. The ac blows super cold now, but it is still making the noise. I turned the ac on with the hood open and I can barely hear the noise from the engine compartment. When I get back into the truck I can hear the noise. As soon as I turn the control from ac to vent the noise will stop. I've run out of things to check. Thanks in advance for any help.

Jason

[j.dehn]

Yesterday the air stopped working while sitting in traffic. When I got out of the traffic it started working fine again. I guess I'll have to take it to an ac repair shop.

Jason

[pipelayerjdh]

Sounds like a good idea. I'm not sure what it could be.