Cleaned A/C Condenser, No Joy

[Boris]

Thought I'd start a new thread.

I spent about five hours yesterday taking apart and cleaning the a/c condenser. It didn't help.

When I arrived on scene, the a/c was working fine. Cold air was blowing out of the vents. The refrigerant drier cannister happens to be located on the small line outside the evaporator. This line was very slightly warm to the touch. The larger copper line going into the evaporator was cold to the touch. The outside of the plenum was also cold (not freezing).

After about 30 minutes, the a/c unit's fan turned off, the furnace fan remained on, and the evaporator line outside the plenum, and the plenum, got warmer.

Time to clean the condenser. I turned off the thermostat, pilled the 40 amp fuse at the a/c unit, and disassembled the side panels, the fan, and any wiring as necessary. The compressor had an orange vinyl insulated sort of pull down 'hat' over it. I took that off, too, to get the compressor specs, if needed, and I put my hand on top of the compressor. It was hot enough that I couldn't keep my hand on it for more than a second or so, but not hot enough to cause immediate burns.

There were lots of leaves in the drip pan, but not much came out of the condenser. I first vacuumed both sides of the entire consenser, and there was not much debris at all. I then wetted and sprayed foam on the outside, and rinsed from both the outside and inside, until all runoff water was clear. Actually, I was surprised at how little dust/dirt there was. The only thing that was really dirty was the temp sensing unit that sits on the small copper line, right where it enters the compressor. I removed it and cleaned it off good.

I got it put back together, turned it on. The outside temp was now 100 degrees. The indoor temp was 77, and I called for 66 at the thermostat. Cool air started coming out, measured at 64 degrees (I guess the attic ductwork was really hot) and it ran fine for about 40 minutes. Then, warm air came out. The a/c fan stopped. I hand checked hand temps at the plenum, and it was warming up again.

Crap.

I'm calling another company out for a another look before I replace anyting major.

[trader_4]

I would look at a wiring diagram for the unit and see what it takes for the condenser fan to stop running. IDK how they are wired, but my first thought would be that the thermal protection for the compressor would stop just the compressor, not the fan too. If that's true, then something else is wrong, eg bad contactor, that is stopping both the compressor and the fan......

[Terry Coombs]

If the condenser fan stops , the compressor will overheat and shut down too ... try it again , and when the fan turns off check the compressor , if it's still running replace the fan motor .

[Boris]

I did find all the specs and wiring diagrams inside the unit when I took it apart.

The schematic will help someone more knowledgeable than I.

When I'm inside the house and I notice the vent air no longer cool, that's when I look outside and see that the a/c fan is not running. So, I don't know if the compressor got hot and turned off itself and fan, or the fan turned off, and the compressor then got hot and turned off. Yesterday, there was one time when as soon as the vent air got warm, I ran to the a/c unit, and the fan was still on, but then within a few minutes, stopped.

[trader_4]

That's an excellent observation. He could check for voltage at the fan when it quits.

[Boris]

"Terry Coombs" wrote in news:ml4ikl$7pc$ [e-mail]:

good point

I've heard 'contactor' used, but not sure what that is. Is it some sort of wiring block where many of the that is stopping both the compressor

Yeah, that was my thought. But three weeks ago, I had the fan motor/capacitor replaced because fan motor bearing was bad and the thing was howling loudly.

[Boris]

never mind to above contactor question...I know what it is.

[J Burns]

[...]

I suppose an infrared thermometer could be as cheap as $10 these days. It won't get good readings from some metal surfaces. If you put a single layer of electrician's tape on the metal, you can get a good reading.

If it happened to me, I'd be interested in temperatures at four places: each side of the drier and each side of the evaporator. The tape on the high side of the evaporator (the smaller tube) should be far enough away that the temperature of the evaporator won't affect it much. Maybe 3 feet?

I'd take my first readings after 5 minutes, when the unit was working well. I'd expect readings along the high-pressure line to be slightly warmer than the outside air.

I'd take a second set of readings after 30 or 35 minutes, when presumably something was causing the compressor to run hotter.

If the high-pressure line was hotter now, that would seem to show that for some reason the condenser wasn't cooling properly.

If now there's a significant temperature difference across the drier, that would seem to show you need a smart guy like Stormy to replace it.

If the temperature on the high side of the evaporator is about normal but the temperature on the low side isn't as cool, that would show less circulation of refrigerant. A problem in the expansion valve could account for it.

[J Burns]

I missed that possibility! When Boris said the fan shut off, I inferred that the compressor wasn't humming, either.

[Ralph Mowery]

A contactor is a relay. You may also hear it called a motor starter. Uaually a low voltage of maybe 24 volts goes to the coil of the contactor. This pulls in the contactor (relay) and puts the 240 volts from the incomming wires to the motors (compressor, fans).

[Stormin Mormon]

Good thing you didn't call me out. Now, it sounds more like bad fan.

- . Christopher A. Young learn more about Jesus .

. .

[Boris]

Stormin Mormon wrote in news:n6ndx.26915$ [e-mail]:

Fan replaced, problem persists.

[Ashton Crusher]

The fan itself could be overheating and might have it's own internal overheat switch so it could stop but still have power to it.

Before tearing things apart Boris could watch for when that fan stops and immediately run water over the condenser to provide cooling and see if the unit continues to cool.

[Tony Hwang]

I say it again, the contctor may be old and contacts are all pitted causuing poor conduction. Was the contactor ever replaced? If fan is wired directly for temporary testing, it'll prove suspicion for the fan.

[Terry Coombs]

The comp may continue to run , but since there's no airflow over the coils , there's no heat transfer , and no or very little cooling . -- Snag

[Terry Coombs]

Look at where the main power wires coming in hook . There's a chunk of "stuff" with all the wires hooked to it . It's job is to hook the power to the motors . There is an electromagnet coil that pulls the contacts inside closed when you apply power . Often the contacts are in the open and can be seen , but not always . It's basically an electrically operated switch for large loads .

[Stormin Mormon]

When the fan stops, does the compressor also stop?

[Boris]

Stormin Mormon wrote in news:KtAdx.21014$eb2.9004 @fx27.iad:

Yes, but I don't know if it's immediately.

[Stormin Mormon]

It helps with the diagnostic, to know. If the compressor stops now or later, that indicates or suggests different parts that can be bad.

- . Christopher A. Young learn more about Jesus .

. .

[Boris]

Stormin Mormon wrote in news:NrEdx.80263$ [e-mail]:

Yes, yes. A chaise lounge, cigar, a few beers, and about 40 minutes is all I need. A pretty assistant wouldn't hurt, either.