I've been trying to figure out why the ac in my 74' isn't working. First off the fan speed switch on high speed is intermittent. Pardon me if I use the wrong terms and please let me know what I should call them. Low and medium speed seem to always work fine. Now on the ac selector switch, the max ac detent quit working but the norm mode still blew air. I had no cold air in norm mode but I had absolutely no air blowing in max mode. I took the car to work and gave it a shot of R-12 and it made the max mode work again. Am I correct in assuming that because of low pressure this is the reason max wasn't working? While I was moving the fan speed switch I watched as the clutch on the compressor would kick on for a second or two then turn off. If I held the switch in place just between off and low I was able to get the clutch to stay engaged and felt cold air blowing. Does this mean the fan speed switch is bad and if so what is the correct name of this switch or relay and where can I buy it? Thanks for any info you guys can give me.