Peter makes an excellent point. Before you do anything, run the A/C for a short while and then feel the A/C and heater hoses. It should help to give you a clue as to what is wrong. The A/C hoses around the expansion valve should be cool and the heater hoses downstream from the monovalve shouldn't be really hot.
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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold
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