Dave thanks for reviewing this.The aircraft is a 1976, P3370232P and was recondition by Riley around 1990. We have not had an oportunity to operate the defroster but we will give it a go next chance and report back. I would expect we should have a comfortable cabin at altitude in the summer months (without the A/C) but it's all the A/C can do to keep up. You have given us some great information and direction and I will let you know how it goes.Thanks.
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