Scott wrote:
OK, I'm struggling with this problem and y'all might be able to help.
I have posted to alt.hvac, but most of those guys are really not very
helpful to homeowners and just tell me to call a tech, and this is a
DIY forum so bear with me.

background:

AC quit working, would cut-out after startup. Thermostat was changed
no result. Called Tech, who tested everything, put 2lbs of r-22 in
it, indicated the condenser fan motor was giving trouble starting and
that likely it had some bad windings or something. Cutting out was b/
c the fan was not working and the compressor would hit the overheat
limit and cut out. He tried changing
the capacitor, no improvement. Wrote an estimate for changing the
motor out of over $500. Being thrifty and handy enough to be
dangerous, I decided this was too much for something I could do
myself.

I looked around and after getting the details on what the motor type
was, I found a OEM replacement at Grainger. 1/4 horse, 220 volt, Y
frame, counter clockwise rotation, sealed air-over, bottom shaft,
etc. I got the motor changed out, substituted the new 12mfd
capacitor
that this motor required (vs the 5 mfd for the other). I took pains
to connect the wires back just as it was before. The new motor had
the same colors leads as the old one, a purple, a brown and a black.

As I tested it, I discovered that this motor does not want to start
either, in fact it makes the same loud humming noise when energized.
When I spun the motor with a stick through the grill and it caught on
and ran normally. Hmm.... The compressor runs strong and has no
issues.

After looking at the way it had been wired when I opened the case,
their are two hot 220 leads and the case is ground. Going from
either
lead to ground is 115 volts. Obviously between the two leads is
220-250 volts.

Of these two hots, one BLACK HOT wire goes to the contactor (relay)
switch and then would connect to the purple fan motor wire when
energized.

The WHITE HOT connects to a wire that goes to a 3 way capacitor (runs
the compressor), with a jumper directly from the input terminal
sending power also to the condenser fan motor capacitor.

The other two condenser fan motor leads, the brown and black, are
connected to the starting capacitor, one on one side and one on the
other. The black is connected to the same terminal as the hot lead.


----


Ok, I thought about it, and using my limited knowledge I figured the
motor has two seprate windings for each hot leg, and by only having
the starting capacitor hooked to the brown wire it was only getting
1/2 the starting power it should have. So, I moved the black fan
lead
to the same terminal as the brown lead, and then the fan would not
run.

I put these back the way they were, and then moved the hot lead
to the brown lead side of the capacitor. Now - the motor started
with
authority, but it ran backwards (clockwise) as you look at the end of
the shaft! DOH!


Based upon the motor you said you were going to purchase (4MB69), it is
a reversible motor. The instructions should tell you how to install the
motor with regard to wiring it as well as reversing the rotation. Do
you have instructions??? Look on the motor if not.


Ok that is where I am now. I have a upstairs unit that is wired the
same way sans capacitor as the motor does not require it.

Any suggestions? I'm perplexed why it runs better in the direction
it
is not supposed to go, and why it doesn't want to start, why the old
motor gave the same trouble. I have a photo of the unit's power box
and can get one of the wiring diagram, but I'd like to get this
fixed. I know it just something simple.


Thanks in advance...


Scott