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Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience:  Manufacture Rep for Major Brand, Technical Trainer, NATE
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I have a Rheem ASL-JEC AC/Heating System with a T855

Customer Question

I have a Rheem ASL-JEC AC/Heating System with a T855 thermostat. The system has been operating well for 6 years. Now every few days the system stops working:
1) The thermostat is call for high speed fan on the outside unit.
2) The furnace air handler is running and blowing air through the house.
3) The outside unit is not running for 10 hours or more while the house heats to 6+ deg above setpoint.
4) The outside unit eventually starts automatically and cools the house.
5) The cycle repeats every few days.
Note: Looking at the control board on the outside unit shows a code of 0 showing operation is not requested even though the furnace air handler is running. I have had a repair man come and he cleaned the outside unit fins really well thinking it was probably overheating but that is not the case. Requesting the fault mode recall does not show any errors stored on the controller board.
I would really appreciate some suggestions if this makes sense! Thank you, Ray
Submitted: 1 year ago.
Category: HVAC
Expert:  Douglas replied 1 year ago.

That thermostat model number does not appear to be the communicating one for that system. It would be either an RHCTST-500 (501 or 551). The 0 simply means it is not receiving a call. If we are just missing the thermostat number by some reason, and it is in fact a communicating thermostat then it would be losing communication. Try to post the whole thermostat model number so I can tell if it's set up communicating. What is the indoor unit (air handler or furnace) model number?

Customer: replied 1 year ago.
I will have to look at home this evening and send you the information. I only copied the outside unit information. I would comment that a Rheem dealer/installer installed the AC/furnace and thermostat at the same time and they have been working well for 6 years.
Customer: replied 1 year ago.
The model numbers on the AC unit and the furnace are both RASL-036JEC. The thermostat is pro1 iaq T855. When the unit is working on high speed the LED display read a capitol "C". When the unit stops, the LED display reads "0". When I recall the fault codes the only code that shows up is a "0". It may be a coincidence, but when I went to replace the cover on the outdoor AC unit I hit the sheet metal with my palms to get the tabs to slip in place and the outdoor unit shut off. Looking at the AC board again showed a "0". When I looked at the thermostat it showed calling for cool and the furnace air handler was still running.
Expert:  Douglas replied 1 year ago.

It would appear there is a loose connection in the thermostat wires at the outdoor unit in all likelihood. You should see a bunch of blue or orange wirenuts under the control box in the outdoor unit. Let's start there by taking them apart and putting them back together 1 by 1. Power down the system inside and out before starting this at the breakers. Let me know how that goes. That is a non communicating thermostat so it will be probably 4 wires. Red, brown, yellow and yellow with a blue stripe.

Expert:  Douglas replied 1 year ago.

Not many hardware stores or home centers have capacitors. Most likely we need to find an HVaC supply house, a grainger. What is your zip code and I'll see what may be around. Disregard. Wrong page and I can't delete my response.

Expert:  Douglas replied 1 year ago.

Let me know how the wiring check goes