My a/c blows warm air when sitting still but blows cold when driving sitting in traffic the other day for about 30mins with a/c on and the temp gauge almost went to the red, can someone give me some advice of what this problem may be.

Sounds like there may be more than one issue. First is to check out the condition of the fan clutch and electric fan to make sure all that is working properly. You can do a search on here and read all about them.

If you resolve the fan issue and it is still blowing warm at idle it may be slighly low on refrigerant. Sounds to me though that the electric fan are not working.

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Jim