Coldspot A/C more trials and tribulations...

[red_october]

Well I got a new motor for the Coldspot A/C, but all is not well. It installed OK, (not an easy process), but now the unit runs strangely. The motor seems to change speed of its own accord and after about 15-20 minutes, it shuts down. Initially I thought this was overheating due to blocking the vent holes with aluminum tape (as recomended by the HVAC shop guys because the motor is outside the room), but removing this tape does not remedy the issue and the motor still acts strangely and shuts down.

I am not sure I wired it up correctly, though, as the new one needed slightly different connections from the old one: on the old motor the was one wire that went right to the capacitor and the neutral wire also went to the capacitor. A wire went from the capacitor (side with neutral) to a terminal on the switch. The new motor has two leads for the capacitor and handles it all on its own. I wired the new motor in by putting its neutral lead to the point on the switch that the neutral side of the old cap went to. This seemed to work.

When the motor shuts off, the unit is still getting power as the compressor will even cycle at this point and will fire up! So is this the motor or my mickey-mouse wiring? Or is it something more insidious?

I also think I may need to re-cap the compressor (the compressor motor cap is about the size of a large beer can!), it sometimes seems to have trouble starting...

 

[red_october]

I think I've isolated the problem

To the thermostat. A quick consultation with "How to Repair Major Appliances" reveals the operation of the thermostat -a bellows and a tube filled with refrigerent! The compessor cycles too frequently, so I set the unit to "Continuous" (remember when this setting existed -what a wonderful thing!) bypassing the thermostat entirely. So far the motor operates at a constant speed and the unit blows air comparable to the Katabatic wind.

What appeared to be happening was that the thermostat was trying to cycle the compressor too frequently, and I'm sure we're all familiar with what happens when an A/C compressor is cycled too quickly- a major power drain occurs and the compressor cannot start. This was happening in rapid succession as the unit tried to re-fire the compressor against the ever-building pressure differential in the refridgeration lines, apparently this eventually caused the fan to slow to a stop (I'm amazed that this doesn't blow fuses or anything!) and I'd guess overheat, because it wouldn't start up again after it stopped thusly unless it had sat for a good long while. I'll keep you guys posted.

That Venetian blind cord isn't bowed out like that for no reason!

 

[polkanut]

Let's hope this solves the problem.

 

[red_october]

Didn't solve it.

The thing has a new thermostat and the motor still conks out after a time. My next brilliant idea is to hook it up to the "medium" lead as this motor is about 5,000 revs faster than the old one anyway, and see what happens that way.

 

[Cybrvanr]

Make sure you didn't reverse the wiring on the motor. The "start" winding is only designed to have power momentarily. It is connected to the starting capacitor and only receives power for a short duration when power is applied. The "run" winding is designed to operate continuously. If the motor is running on the start winding, it will run a little bit faster than it's design spec, very hot, and the thermal cutoff will shut it down after it gets too hot.

 

[red_october]

This motor that is in it apparently handles that all on its own; there are two leads that come from the capacitor and don't go to anything else. At least that's how the guys at the shop showed me how to wire it up. I changed the active wire to be the "medium" setting; I'm guessing that will be around 1,000 RPM, which is what the one in it was pulling when it actually worked (actually something weird like 1,150).

 

[red_october]

Updates....

Well here's the latest news from the front:
I changed the active wiring to medium, the motor still conks out after 20 minutes or so and won't go back on until some time has passed. This happens on fan too, so we can rule out any interaction from the compressor, although it probably needs its enormous capacitor replaced. I suspect the motor I was sold is faulty.