I watched the video. Does the G terminal stay energized when you turn call for cooling? If it does then that suggests the control module may be the problem. There is a spade connector labeled "cool" on the control board. I believe that is connected to the blower motor and should be energized when the fan is turned on or when the thermostat is calling for cooling. Check the voltage on this terminal for both conditions.

In that video, i believe the multimeter is measuring the green (fan) and blue (common) terminals. Would that indicate the fan is losing the proper voltage when the cooling actually kicks in? I took a video of me measuing the voltage between the ”cool” and fan common wires…showing ~70 volts and then drops when cooling is kicked in like the above video but that file is too large for me to upload.

The thermostat is powered by a 24 V transformer. Your transformer is putting out about 26V when loaded which should not be a problem.

The cool terminal when energized should be at 115 - 120 V. This is sounding like a control board problem.

The tech checked refrigerant levels, replaced the blower motor and capacitor but didn’t think to check the fan voltage level?

When he was here the first time, he tested freon and it was fine. He tested run capacitor and he replaced it. He checked wiring in the air handler and said it was working. He left and less than an our later the fan cut out. He came 2 days later and said the fan needed to be replaced because he thought it was an overheating issue. I ordered and replaced the blower motor and it did the same thing. Thats when I came here because on techs want to return my call to even come and look at it including the first tech that has come twice already.

“The cool terminal when energized should be at 115 - 120 V. This is sounding like a control board problem.”

This it testing the ”cool” and fan common spades when running correct?

"measuring the voltage between the ”cool” and fan common wires…showing ~70 volts"

This is an indication there is an open neutral with no load on the circuit. There is a terminal block of male connectors on the control module with 4 or 5 wires plugged into them, they will all be white. These are the high voltage (115V AC) neutrals going to the high voltage components. One is also the neutral wire coming from the junction box from the main power input.

I believe you have a bad connection someplace in one of the neutrals, more likely the one from the junction box or the one from the Module neutral terminal to the blower motor. Check wires, any wire nuts and the terminals. I'm thinking if you wiggle one of those wires the blower will work so pay attention to what you wiggle so you can fix it.

When troubleshoot should always start at the power supply hot and neutral. The voltage dropped lower when the fan was energized, and beware, there is a chance components could be destroyed when an open neutral causes the chassis ground to becomes a neutral .

1. Do you have a two-stage air conditioner (described on page 27 of the Installation Manual)?
2. Are there wires connected to both the Y1 and Y2 thermostat terminals?
3. Have you run the Nest Thermostat Cool tests to check the connections and operation (testing both cooling stage 1 and stage 2 if available)?

"I service the Katy, Texas area."

Your attempts at advertising should at least note your service area excludes any locales that require permits or inspections.

I ordered and replaced the blower motor and it did the same thing.

Kevin9408's suggestion that there is a bad connection seems plausible given you replaced the motor. This could be caused if motor wiring does not have the same type of spade connector as the control board. I do find it mysterious how the motor can operate when the thermostat energizes the "G" terminal, but no when the "Y" terminal is energized. I would disconnect the motor and verify the "Cool" terminal on the board is at 115 V in both cases. Then repeat the voltmeter measurements with the motor wiring securely connected.

This furnace can be configured to work with a 2-stage AC condenser. It requires a 2-stage thermostat (Y1 and Y2) and a relay had to be installed in the furnace to have the motor operate at a low and high speed. I doubt you have this configuration, but it is something to verify as part of the debug process.

Mike, you did ask the question but I could not understand his answer. 70v across between the ”cool” and fan common wires make no sense and I suspect he doesn't know what he is doing. If he is still alive after probing wires in his furnace he might clarify what he's doing. We need a reset.

Your question was; "Does the G terminal stay energized when you turn call for cooling?" this may be somewhat confusing to a layman.

My question to Sinclair now; when the you turn on fan to "FAN ONLY" does the blower run? YES or NO. Until then I'm finished here.

When someone is measuring voltages I assume it is with respect to ground or a reference. I agree the 70 V reading is very strange. Your idea this being caused by a floating neutral is quite good.

My understanding so far is the blower fan will operate (possibly at a reduced speed) in the fan only mode, but then stops when the thermostat calls for cooling. Sinclair can confirm the behavior.

Turns out the replacement control board fixed the problem. Thanks for the replies!

Just out of curiosity, will the HVAC contractor be reimbursing you for the cost of parts they replaced that weren't related to the root cause of the problem?

Just curious: Are thermostat wires connected to both the Y1 and Y2 terminals and if you run the Nest Cool Test does it recognize two-stage cooling?

Just out of curiosity, will the HVAC contractor be reimbursing you for the cost of parts they replaced that weren't related to the root cause of the problem?

Charles contact the local permit office, they could help you with that. LOL.

The technician's poor troubleshooting effort pumped up the cost of the service. If the blower motor and capacitor didn't need to be replaced, I suggest the OP negotiate a discount based on that.

Given that the system worked in "Heat mode", that pretty much eliminated the capacitor and blower motor. The guy didn't have a clue. I agree with Charles.

The tech stated the blower motor needed to be replaced. However the original author replaced the motor. The tech did replace the motor capacitor. It may have an out of range reading so replacement might have been warranted. Tech is not returning phone calls. Returning money is highly unlikely.

Whether the tech replaced the blower motor or the OP replaced it at the tech's direction doesn't change the fact that the troubleshooting effort was poor at best. I'd expect some concession on the service call cost. If not, the OP knows which company to avoid the next time there is a problem.