Good morning folks. I've got a 1995 Blazer that has developed a surge after getting the a/c replaced. It runs fine with a/c off, but when it's turned on it will start to surge. Transmission was just flushed abs serviced. Also it's stuck on defrost, while before it went in, you could move it from defrost to face or feet. Don't know if coincidentally or if a vacuum line is off. Any ideas?