2000 Montero Sport LTD. A/C would cool for a while then go warm. I figured it was due to air/moisture in the system. I put a gauge on the low pressure side when engine was off and found the pressure over 150 psi. I'm guessing the previous owner just pumped more freon in without understanding anything about pressure. I just picked it up from the shop. They sucked out all the old freon and refilled to the correct pressure. Now there is very little if any cooling. The low pressure side increases pressure when the compressor comes on and falls back to normal when the compressor shuts off. The tech was perplexed and was ready to start tearing things apart to try and isolate a flow problem. In interests of saving money, I told him to settle down. I'll see if I can get more info from this forum or elsewhere to try and pinpoint the problem. Any comments or advice?