Thermostat not activating Condenser

I’m hoping for some advice on how to properly wire my Wyze Thermostat. Any assistance is GREATLY APPRECIATED as I’ve reached the end of my trouble shooting knowledge. I have two completely separate HVAC units (one for upstairs and one for downstairs) and have the same issue on both. The issue is that when in cooling mode the fan runs, but not the condenser on the outside of the home. The heating mode runs as it should. The wiring is different for each unit, so I’m describing the more straight forward unit in hopes it will reveal the problem on the second. There is 18/5 running directly from the thermostat to the panel on the HVAC unit. I hooked it up with the use of the 5th “common” wire as directed, but the thermostat wasn’t receiving power. I hooked it up with the common wire adapter (i.e. didn’t use the 5th wire) and the thermostat received power. The unit runs as it should for heating, but with cooling, only the fan runs and no condenser. I’ve checked all connections and arrangements and all is as it should be… at least so I thought. To double check I hooked the old thermostats back up and both units operate as they should. Below is a photograph of the existing wiring at the HVAC Unit. (I believe the blue/common wire was hooked up with the install of the unit, but it is not in use as it is not connected at the thermostat). Due to to photo limitation I’ll follow up with a photo of the thermostat. These are prior to any modifications for the new thermostat. Thank you to all who reply!

Following up to original post with existing thermostat photo. Thanks again!

so do you have 2 thermostats?

the 1st install attempt, was the blue wire behind the old mounting plate? If so, there must be another connection between there & the control board, unless the wire is bad.

do you have post install pix?

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Thank you for the reply. There are two thermostats, serving two separate systems. I actually managed to get it up and running a few minutes ago. I was incorrect in thinking the blue common wire had no active use. Which is exactly what you mention above. There must be a splice in a location that I can’t see. I’m placing post install picture of the working configuration that will hopefully help others.

Working set up for above troubleshooting.

Working set up (2 of 2) for above trouble shooting.

cool, glad to hear

You need to find the splice and remove it. Right now, the wyze cannot run just the fan without running the condenser as well, which can lead to freeze-ups and compressor damage in the winter.
That yellow wire should be a continuous run from the thermostat to the C adapter and there should be a separate continuous wire going from Y on the air handler to the compressor outdoors.

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Thanks Speadie. After I thought I had it figured out, that was definitely an issue. The system worked as planned except the compressor was running at the same time as the heater. I chased down the splice and routed all wires appropriately. Everything is now working as it should and I did not need to use the C adapter. There is a splice mid line for the yellow and blue where those run out to the compressor. Ensuring the yellow and blue also run from thermostat to the air unit while accommodating the splice to the compressor has the system running as it should without the C adapter.

The last thing I did was I ran through the set up for the thermostat again. I wouldn’t have thought that to make a difference, but when I reset the thermostat and ran through the install again I noted that a C wire was present. This last step got it working properly after I got the wiring straightened out.

Thanks again for taking the time to read and respond!