On Mon, 2011-07-11 at 07:34 -0400, M.L. wrote: > On Sun, Jul 10, 2011 at 9:04 PM, Herbert Graf wrote: > > The central air unit at my home has stopped cooling at around noon, on > > Sunday, the past 2 Sundays. It starts working again around 8-9pm. > > > > The symptom is the unit is "on", i.e. the condenser fan is running > > (including the furnace fan), but the compressor is not. The coolant > > pipes are both ambient temp. > > > > At around 8 or 9pm it starts working again, and works for the entire > > week. >=20 > If it happens at exactly the same time for two weeks, you can suppose > that it's a logic/controller issue instead of a mechanical issue. > Because the compressor works for the whole week except for 8 hours, it > would stand to reason that it really does work just fine. >=20 > Try manually enabling the compressor using the contactor that switches > on the compressor. I'm not sure how it's arranged on these units but I > guess you would probably be able to cause it to close with your > 24/26VAC signal. During the problem period the compressor has power, as measured at the compressor terminals. The only solenoid is receiving it's 24VAC, and the condenser fan is running, proving the solenoid is working. There are nothing but wires between the solenoid and the compressor housing. I've been looking things up, and it just happens that the past 2 Sundays have been the hottest weekend days of the summer, by a couple degrees (high of 30C on the 3rd, and a high of around 32C yesterday). It's looking like I've pretty much covered everything, damn. Thanks, TTYL --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .