Heat Pump Air Handler won't shut off

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  #1  
Old 11-21-13, 11:12 PM
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Heat Pump Air Handler won't shut off

Hello,

I have a Ruud Heat Pump Air Handler, Model HQA, that is constantly running even when the outside Heat Pump is off. 2 weeks ago it started, I replaced the Thermostat and the unit began working appropriately. Today, the Heat Pump Air Handler, fan, and perhaps Emergency Heat ran all day. This evening I removed all of the wires from the tstat and the Heat Pump Air Handler and fan continued to run heating the rooms. I reconnected the tstat and turned the temperature up to make sure it was still able to control the outside unit, which worked as expected. I went up in the attic to check out the Heat Pump Air Handler and look for any signs of issues was surprised to see how clean everything looked for a unit that is 25 years old. Now that I believe I have eliminated the tstat as the issue, could this be a relay issue? If so, any idea which relay? I have included links to the pictures of the wiring in the heat pump air handler for reference. Your support is appreciated in advance.

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Old 11-21-13, 11:18 PM
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Welcome to the forums.

You don't have a thermostat problem. You have a defective sequencer in the air handler. It's job is to turn on the fan and the heating coils. It is getting stuck on.
 
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Old 11-21-13, 11:29 PM
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Thank you PJMax! How would I go about replacing the sequencer in the air handler? Specifically where is the sequencer located in the air handler?
 
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Old 11-22-13, 02:04 AM
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I can't tell if there is one or two sequencers there.

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Old 11-22-13, 08:21 AM
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Hello PJmax,

Sorry for not taking another picture with a birds-eye view. I believe there are actually three sequencers there. I will need to take apart the unit again. In continuing to troubleshoot last night, I ran the tstat through the "cycles", pausing 20 seconds after each one (cool, heat, emergency heat, and off) when I ran through the cycle the second time, the tstat triggered the heat pump air handler to return to normal operations. I am sure it's going to stop working again, so I want to make sure I get the replacement parts soon and fix the issue.
 
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Old 11-23-13, 08:54 AM
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Hello PJmax, here is the top view of the picture you added an arrow to. It appears there are two sequencers?

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