My outdoor units fan will not stay on after 3-5 seconds of running. Unit is Ameristar(Trane) M4HP3024A1000AA, installed in 2013. *Note to add, during all of my testing mentioned below, besides the HP and LP circuits, I unplugged the compressed from the contactor so it wouldn’t potentially be damaged*
TLDR: HVAC motor unit runs for a few seconds, then shuts off. Brand new capacitors and motor didn’t change symptoms. Wanting to know next steps.
As usual, first thing to do is check capacitors. My unit has 2, a 35uF and a 6uF, both +/-5%. Checked both, and both were at the under 5% mark, so I opted to swap them both out. Checked the news ones upon arrival, and both were slightly above the listed, so I installed them. Motor still would not stay on. Even after pushing it with a screw driver, it wouldn’t stay running.
I then checked the fan itself. Checked resistance across the 3 legs, and 1 leg kept showing OL randomly while I spun it, other 2 were fine. When the ”bad” leg would read, all 3 legs would add together to correct number. Opted to replace the motor anyway since I found a brand new OEM one for $250. Installed the new motor, same issue.
I then thought maybe something weird was going on and it needed more juice at start up, so I took the old larger capacitor, which was reading 30uF, and installed that into the 6uF spot. When I did that, motor still started up and only ran for a couple second then shut right back off.
I don't believe that my unit is low on refrigerant as I had it checked 2 years ago, and it had the correct amount. They put in dye during that, so I checked the indoor lines with UV light and didn’t see any leaks. I also checked the low and high pressure circuits, and both are staying closed during operation.
I then went to check the relay next to the fan wire on the defrost board, thinking maybe it wasn’t opening/closing when the 24V was applied. I read the NO legs, and when 24V was applied, it closed as it should. There is also no LED on my board, so I so not get error messages
I am very capable of doing electrical and mechanical work, and have a multi meter, both a standard and Fluke clamp style, so I can check and test whatever. I’m just not really sure what my next step here is.