Reply To: Reb Moshe on Shabbos Clocks

Its possible that there is no psakfrom gadolei yisroel in the pre war/ post war era dealiing directly with AC systems given that most since very few shtieblach had central air conditioning systems. There were occasional references to fans but those don’t generally deal with whether they would be treated in the same way as lights for purposes of whether it was OK to have the shabbos goy turn them on/off. Likewie, the issue is futher complicated by whether using a programmed thermostat to turn on the AC systems would be a question o maris ayin or zilzul shabbos. Very few batei medrash/shtieblch in the Alte Heim had AC systems with thermostats so it wasn’t an issue