Air Conditioning - AC ignores thermostat, stuck in temp range

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ireenee
06-13-07, 06:34 AM
Rheem AC and Robertshaw 9600 thermostat (both 4yo) stopped talking to each other. Thermostat NOT programmed. I manually set 80 when not home; 74 when home. Recently something gone wrong (not the batteries!). Get home, room temp is 79, and i turn thermostat to 74, i hear click indicating that set temp got below room temp, but AC does not turn on. ONLY when room temp goes up to 80, AC turns on, but only works until temp goes down to 77, then turns off. Keeps doing that, does not listen to thermostat. Temp range 80 to 77. I RESET thermostat and notice that default temp is 78 when everything is zeroed-out (not sure if that means anything). AC still will not turn on if room temp below 80. Also, if i just switch from AUTO to ON, still nothing. When AC does come on at 80, the air coming out is very nice and cold, so not Freon issue, and not fan issue.
Called ROBERTSHAW, they told me that if i hear the 'click' when i set temp below room temp, then it sends signal to AC, but the AC is not receiving signal. Basically they claim thermostat OK.
So i cannot understand if problem is in thermostat, the AC, or the link between them!!

Ed Imeduc
06-13-07, 05:56 PM
If you jump R-Y-G at the tstat does it all come on????? If so Id say its the tstat. Now you can have a time delay on the unit that will take it a little bit to come on.
furd
06-13-07, 06:25 PM
That thermostat has a built-in 5 minute delay on the cooling cycle to prevent compressor damage from short cycling. If your compressor also has a delay timer then it could be 7-10 minutes from the time that you manually lower the temperature setting until the compressor starts.

The thermostat also has an adjustable differential setting of 1 to 3 degrees so cycling from 80 down to 77 and then back up could be entirely normal.

I suggest that you carefully follow the programming instructions in the user's manual. If you do not want the thermostat to operate in the program mode you may then switch it to manual.

The AUTO-ON switch controls the fan (inside) only and will have no effect upon the cooling cycle.

http://www.icca.invensys.com/manuals/robertshaw/110-653B.pdf