Mysterious Behavior on my Window AC

[SilverDollar]

Hi -

If I can save/repair my Air Conditioner I'd like to try. I'm not an engineer or electrician, but I'm "handy" and can follow instructions. Here's my problem...

The unit is a Friedrich 18,000 BTU unit, installed in a sleeve in a window of my apartment.

The unit will run fine for up to 20 minutes, with nice cold air blowing into the room. Then suddenly, the blowing air will stop, though the compressor sounds like it's still on. When this happens, I turn the unit off.

For several hours after one of these shut downs, I can't get the thing back up. If I press the "COOL" button, I hear the compressor, but there's no air blowing into the room. If I press the "FAN ONLY" button, absolutely NOTHING happens at all... no click, no hum, nothing. Just like pressing the button of a unit that's not plugged in.

Lastly, if I wait from several hours, to sometimes overnight, then I'm back up and running; with cool air blowing, but only for up to 20 minutes.

Also, if I shut the thing down BEFORE it stops blowing, I can reliably start it up again anytime I want. But if it runs long enough that it stops blowing on its own, then I have to wait several hours before I can use it again.

Any clues or proceedures for me to trouble shoot this problem? I can make simpler repairs if that's all that's needed. But a certain point, I guess I'd just buy a new one. This one is around 15 years old.

Many thanks for your help!
Lance
(SilverDollar)

[HayZee518]

check to see if the evaporator is freezing up. a coating of ice on the evap coils will stop air flow through it. lack of freon in the system most likely will freeze up the system. also if the room temp is somewhat lower than the unit will cause a freeze up.

[kactuskid]

It may need a good cleaning. Here's a link to show you what to do, let us know how it goes.

http://www.bobvila.com/HowTo_Library...ing-F2199.html

[SilverDollar]

HayZee - thanks for your reply.
you said "a coating of ice on the evap coils will stop air flow through it. "

Ice would account for the way the machine seems to "get better" if I wait long enough. But you say "stop air flow". I'm not dealing with a air flow that gets slowly more and more restricted, this is a fan that suddenly stops. It goes from fine, to dead stop in an instant.

I'm going to try a little experiement. If I turn on "FAN ONLY" and leave that run for a while and it does not lock up, that would eliminate the possibility of ice, wouldn't it?

I'll do that today, it will be hot here in NYC today, and will let you know.

kactuskid - Thanks for the link to the cleaning article. I read it and will read it again when I have the unit out of the window. I don't think any cleaning issue would account for the symptoms my AC is showing, do you?

Will talk again, thanks,
Lance

[SilverDollar]

Well, here's another piece of the puzzle.

I just tried to turn on "FAN ONLY". Nothing happened. It's dead. For now.

I may have over simplified a bit in my original post. Sometimes it does come back to life after a few hours. But sometimes it takes a few days. In this case, the last time I had air blowing into the room was yesterday, maybe 24 hours ago. Yesterday was hot and I think any ice would have melted by now.

I will try the fan thoughout the day. My experience has been that at some point it will suddenly start working again. I've been limping along by running it for 2 or 3 minutes at a time and then shutting it down. I can keep the room from becoming unbearable that way and the unit doesn't self destruct. If I get greedy and try to run it longer - she stops blowing and then I have to wait. Like I'm doing now.

[HayZee518]

could be motor bearings. bronze bearings in some cheaper motors could heat up the shaft expanding it and stopping the rotation. most of these are free floating self aligning type within a felt lubricator which should be oiled with a non detergent oil light weight. 3 in 1 oil won't do!

[SilverDollar]

I'm back with the results of my "FAN ONLY" tests - and it sounds like they might further point to a motor problem.

Yesterday, I turned on the "FAN ONLY" and let it run without any cooling. It ran for a long time, maybe more than an hour. This is much longer than it ever ran when I turned on "COOL". After about an hour, the fan stopped. This with no compressor running, so, no cooling, no ice. I repeated this test twice, with a several hours betweeen.

Ok, so, HayZee, you're thinking motor bearings? You said cheaper model, not the case with this Friedrich ($$$), but the unit is 16 years old. If it's just a lube problem I can handle that. I does not sound like an electrical problem, do you agree?

Ok, let me try to get it out of the window, open it up and see what's what.

I'm sure I'll be back with questions when I get going.

Lance