Hi Everyone,
I have Robertshaw 9500 thermostat which has a problem with room temperature stucked at 77 degree. No matter what setting I set at, either lower or higher than 77 degree, the temp is still shown on the thermostat at 77 degree, even after running for 1 hour. And the system does keep on running until I turn it off; producing cold air as normal. (Please note I don't have the fan set ON for continuous run).
So I thought perhaps the thermostat broken; needed to be replaced. I opened up and found the following connections:
RED connected to RC with a factory jumper clip from RC to RH
WHITE connected to W
GREEN connected to G
YELLOW and BLUE both wires connected to Y
B O not used
How is it that YELLOW and BLUE both wires connected to Y terminal? Please see link for pix.
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I am thinking of getting another digital, non programmable thermostat from HONEYWELL with same terminals, RC/RH/W/G/Y/B/O. My question is should I connect both YELLOW and BLUE to Y terminal on the new HONEYWELL thermostat? Any advice would greatly appreciated. Thank you all for your time!
Chris
Does the temperature actually drop below 77F after a few hours?
Only 1 wire should be connected to Y - can't tell what the blue wire is for without checking the air handler.
No the temp is stucked at 77 degree. No matter if I set temp higher or lower. System keeps on running, producing cold air until I manually set it off to shut down system.
Any idea Muggle? Thanks for yr time!
Ps I check tomorrow see what's the blue wire connected to in air handler. Pls note system worked fine for the past 2 years until this past Friday that temp stuck problem arises.
If the house cools down drastically but the stat stays at 77F, replace the stat.
Anything by honeywell will do the job - rth4300 is a good option.
Otherwise, the system isn't cooling well and you should get it checked.
Update - I open the control panel and trace the yellow and blue wires. As it turn out, there are 2 condenser unit on the roof, instead of 1 unit. So basically connect both yellow and blue wires to Y terminal to call both condensers once cool setting kicks on. I replaced the old thermostat with Honeywell and everything seems to work fine now. Thank you Muggle for yr help and others for reading #128513;
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