AC blower not working, and it's HOT outside...

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Old 08-04-20, 07:59 PM
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AC blower not working, and it's HOT outside...

While it's not projected to hit 120 anymore, it's still running ~110 here. The sooner I get this fixed for a reasonable cost, the happier I'm going to be.

Not versed in AC units, but I understand the basic function of the unit and most components. I need direction in diagnosing and isolating the problem. Here's where I've gotten since it stopped working sometime midday:

Trane XL1400 3-1/2 ton system
-Condenser coil fan works
-Compressor sounds like it's working, and the radiator (cooling core under panels) is cold to the touch when running.
-Blower fan is not turning on (not even when spinning the blades by hand to assist in starting).
-Dual run capacitor looks fine and tests fine (40/5F spec, and I forget what I got, but essentially right on)
-Start capacitor looks fine, but tests high (internet usually addresses low test as bad. Not much about high reading). 135-162mfd spec, and I'm getting just shy of 220F.

Getting a new start capacitor is a cheap and easy way to make sure that's not the problem, but I'll have to wait until morning to hunt for one locally. If not available, I'll have to wait 6 days for delivery from Amazon (but it's only $8).

Indicator light on blower motor board lights up when fan is turned on at the thermostat, so it appears it's getting the signal to turn on, but either no power is making it to the motor, or the motor has taken a dump...


Request photos as desired.

Blower motor board is the one on the left, middle.

Blower motor board

Blower motor board

Blower motor board

Blower motor

Schematic from panel
 

Last edited by Doctor Jelly; 08-04-20 at 08:07 PM. Reason: Photos
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  #2  
Old 08-04-20, 08:40 PM
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Welcome to the forums.

XL1400 is the series..... not the model number.
From your description you have a packaged unit ? Everything in one cabinet... outside.... is that correct ?

That is an ECM motor in the picture. It's controlled electronically. It does not use a capacitor.
The capacitors are for the condenser fan and the compressor.

You can replace that motor or take it apart and work on it. The part # D341314P42
Motor parts to view..... Ebay ECM parts
Google ECM Genteq motors or Genteq ECM 2.3 and you'll get many hits and tutorials on servicing them.
 
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Old 08-05-20, 04:45 AM
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Here is the thread that discusses trying to repair the control module on ECM motors.

https://www.doityourself.com/forum/a...e-motor-4.html
 
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Old 08-05-20, 11:23 AM
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@PJmax
Model # per your earlier request:
WCY042G100BA


Here's where I'm at since I started back in it this morning after a fitful and short slumber in a ~90 house:
Using PJmax's search suggestions, I found line power is good (PDF from thedealertoolbox.com), and low voltage control is good enough (terminal 1 to 15 is 16.8vac instead of 24vac, but 1 to 12 tests at 24vac. This is ok per the reply to Marc2theMax's youtube comment).

Motor: Specs out fine at ~5.2 on each coil (<20ohm spec), and OL for each to chassis ground. Motor spins fine by hand.

Thermistor: Per various sources, it seems the thermistors are a known fail point on these. Mine appears fine, and tested fine at 1.2ohms (I think it was ~1ohm spec). No other obvious failures on top side of board.

I removed the board just to see if there were any obvious failures on the backside, as I'm pretty well out of common failures to look for at this point, and sure enough, there is a blown fuseable trace. I'm working to get someone with better tools and skill than I to solder a jumper on this afternoon. If it doesn't work, I'm considering a used unit for ~$200 shipped (motor and board) that can be here in 4 or so days.
Per "t" in his review of the Zebra thermistor repair kit on Amazon, he had a burned trace too. Says his research indicates it's a shorted microchip under the potted material. If so, oh well, I was going to have to buy a replacement anyway. If this works, then hooray for money saved!

Couple other places mentioned burned traces for various motors in mostly furnace applications. No photos matched my board exactly. Only one guy said he jumpered his and it worked fine. I will make sure I follow up if this turns out to be disastrous or not.

Top side of board with thermistor (pink oval in the middle)

Back side of board with blown trace

Closeup blown fused link trace

Locating blue wire for reference

Locating blue wire for reference
 
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Old 08-05-20, 06:46 PM
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Kaboom as soon as I threw the breaker. Anyone want a grenaded controller?


Circuits blown away everywhere!

The jumper post kaboom
 
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Old 08-05-20, 07:21 PM
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I got here too late.
Yes.... that's a fusible link. You needed to check for what was shorted and caused that to open.
Quite a blast.
 
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