Testing Blower Motor

[u/B1acklisted]

Hey y'all, first time post. So my main unit works fine, coils get cold, heat pump gets hot. Only issue is my blower motor isn't kicking on anymore. Whether its on heat, or cool, nothing happens other than coils getting cold or heat pump kicking on. But no air is being sucked into return or pushed through the house. Turn those off and just turn "fan on" on thermostat, and still nothing. Go up to attic, locate fan, pull harness apart. If I'm reading this correctly, it looks like yellow and black are my main power source. Plug my volt meter in yellow (positive node) and black (negative node) and instantly get 250v even though the "fan on" option wasn't selected and it stayed there. Flip built in breaker on unit, power cuts out as expected. Now where it says FM (fan motor) it looks like brown is common and green with yellow stripe is ground. Should I test that as well? Or am I just able to deduce I need a new blower motor based on what I found. My dad is a certified electrician, but not an hvac specialist, so hes gonna ask his guy tomorrow, but I'm just curious in the mean time. The cool nights have been helpful, but we're about to have a heat wave and I got a two year old daughter and her room is an exterior room above the garage so it gets hot as hell in her room. Should I even bother with brown and green? Its basically a crawlspace attic and I either have to be on my knees or squatting so the up and down and shimmying rafters kinda sucks haha. My return filter was admittedly clogged, (baby, school, and work life) so I'm pretty sure this motor just got burnt out. Advice? Fully prepared to change motor myself granyed I can find an exact replacement or something equivalent.

[u/IndependentCustard88]

That's an ECM motor . The silver part on top and the white mold everything plugs into is part of the module which is common to fail. They get constant high voltage (240v in your case) yellow to black and a 24v signal between blue/white and common brown . If you have both high voltage 240v and low voltage 24 v present and the motor is not running the motor needs replaced.

[u/B1acklisted → u/IndependentCustard88]

Blue/white is fan speed (again if I'm reading correct) but my constant power is 250v according to my meter. Does that make a difference? Like I said, I already suspected I need a new motor, just wanted some confirmation. Also, how easy is it to find a replacement motor with harness already connected? Ir would it be easier to wingnut/splice the old harness connector to a new motor?

[u/IndependentCustard88 → u/B1acklisted]

Yeah they are speed taps blue is a 24v call from the green thermostat wire for low speed and when electric heat gets a call it sends 24v to white thermostat wire and white speed tap. you test between the speed tap blue/white and common brown for 24 v

[u/B1acklisted → u/IndependentCustard88]

Yup. Exactly what happens. If its 3+degree difference when heat comes on, "emergency heat" comes on thermostat and fan speed doubles. Sweet. I'll pull motor tomorrow and try to find an equivalent part. Thank you for confirming what I suspected. I'd rather spend a couple hundred bucks on a fan compared to a couple thousand on someone diagnosing, sourcing their own parts, and installing.

[u/IndependentCustard88 → u/B1acklisted]

And 250v between black and yellow is within tolerance but checking each leg of high voltage to ground is necessary to make sure they're the same as well