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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8769
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I unplugged the drain on my HVAC system at the air handler

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I unplugged the drain on my HVAC system at the air handler while the system was running and it turned off at this time. I then went out and vacumed out the drain from the outside because I had a clog. The system will not turn on again. How do I fix this.
Welcome to Just Answer!.

I will stay with you until the situation resolves.
I hold questions open after positive ratings to allow for unlimited follow up.

It sounds like your system has a float switch in the coil drain pan or in the drain line itself... it will have two wires going to it...its small about the size of an egg.. if the drain line clogs up the switch will open and keep 24 volt control ;power from starting the outside unit.

you may have caused the float to stick in the up position by blowing the drain line out..there would have been no permanent damage... Look for the float assembly and clean it. Let me know how that goes.

As long as you keep rating my coaching positively, we keep going without any time limit.

Customer: replied 4 years ago.
I got the float to work and AC to turn with thermostat in on position. When I change thermostat to auto position it turns off again. The float has been cleaned.
Hello again, good work on cleaning the float.

the issue with thermostat ON or Auto sounds like a possible wiring error... Is this a new system? Can you tell me what color wires are attached to the thermostat, and what terminals each color of wire is attached to... and the brand and model number of the thermostat?

ON and Auto are not common settings for cooling or heat mode...but IS a common setting for the FAN... is that a switch marked FAN that has the option of ON or Auto.

Let me know, we can go from there.

Customer: replied 4 years ago.
The system is a little over three years old. It is a Hobeywell thermostat with model RTH3100C or PRO TH3000. I have two units. The wires are white, yellow, green, orange, red and blue. White is connected to terminal E. yellow to Y. Green to G. Orange to O. Red to R and blue to C.
Customer: replied 4 years ago.
The auto and on setting is under the fan mode.
Hello again,

The fan should run constantly no matter if the system is in heating or cooling mode or calling for heating or cooling...if ... it is set to ON.

If it is set to 'auto' then it should only run when the system is actually heating or cooling.

You problably already know that... I just want to make sure we are in the same page.

It may be that you cleaned the float switch but that the switch contacts are still not closing, keeping the cooling function off...but allowing the fan to run in FAN ON mode

To test that put a jumper wire between the two wires that connect to the float switch..

We can go from there.

Customer: replied 4 years ago.
I appreciate you help. The system is cooling now. I will check that and my AC guy is coming out later this week to check things out also.
Hello again, if the system is working now, you may not need the service call... if you have a clean air filter in it and the fattest copper tube connected to the outside unit runs cool, but not icing, it is in pretty good shape.

A really good service man though will go through the system and tighten all the wire terminal connections, especially at the outside unit... that would be a good idea, but you can do that yourself with the power OFF.

I work on my own time here at my own expense, the company only pays me part of your deposit if you rate my service 'good' or 'excellent'

If you do that, I will hold the question open so you can follow up days or months from now on the same dime so to speak..


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