On a recent visit to Demo's for A/C work I drove away with it working fine (after surviving a year in Houston without it!). The next day the system seemed to have lost about half of its cooling power and I took it back. My '91 truck is getting a bit old now, and it turned out to be a seal gone bad in a part of the system that had tested okay when they fixed it and it also wasn't a part of the system that had been worked on. They fixed it for no charge while I waited and I was back on my way.
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