Very strange A/C behavior


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Old 05-16-15, 10:24 AM
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Very strange A/C behavior

Background: Several weeks ago, a raccoon found his way into my attic and shredded the silvery Mylar-and-wire ducts installed when the A/C was replaced. I patched the long 12-inch duct, replaced the others with stretchable aluminum, and wrapped it all in insulation. All was well for a few days. Don't think I messed anything up in the repairs or missed any damage the visitor did. If there has been more damage since then, I haven't found it.

Suddenly, the A/C doesn't work. It's set for 75. The living room is now 80. It will reach 83 before the outside temp comes down. The air conditioner comes on once in a while, apparently at random, runs for a few minutes to no obvious effect, and shuts down. Okay, bad thermostat?

Maybe not. When I wake at night, the unit is usually running. When I get up in the morning, the temperature is whatever the thermostat is set to. I have tried it as low as 73. Natural cooling, windows open at night, does not get the house below 78 or 79. I've checked.

This is really starting to drive me nuts, and summer is coming. Help? Please?
 
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Old 05-16-15, 10:33 AM
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Turn the power off to the furnace. Take the stat off the wall to expose the wires. Remove R wire, Y wire and G wire then twist them together. Restore power. Does the fan and AC run?
 
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Old 05-16-15, 12:26 PM
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They do! Time to replace the thermostat?

This is a non-programmable Honeywell, model number TH5320U 1001. Is there anything I should know, or do I just take it into the big blue (or orange) box and tell someone I need to replace it?

Many thanks for the clue. (Still can't figure out why it seems to work at night, though.)
 
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Old 05-16-15, 12:32 PM
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It's not terribly clear trying to follow your problem. You need to determine if the problem is the inside blower or the outside condensor.

If the inside blower is on without the outside unit.... the air won't be cold.
Are both units off ?
It's easy to blame the thermostat but rarely they are the problem.
 
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Old 05-16-15, 12:35 PM
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Rats! Five minutes later, the compressor and fan both have gone off, though the thermostat wires are still connected. This feels like some sort of thermal protector is tripping, which might explain why the system works in the relative cool of the night. More ideas rather desperately needed.

Thanks again.
 
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Old 05-16-15, 12:50 PM
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the compressor and fan both have gone off, though the thermostat wires are still connected.
Are you saying that the inside fan and the outside unit BOTH stopped working ?
The condenser is thermal protected but the inside fan should still run.
 
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Old 05-16-15, 01:25 PM
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Yes. Both stopped and have not come back most of an hour later. FWIW, the fan was set on automatic. No idea whether that has any effect now that the thermostat is no longer in the circuit.
 
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Old 05-16-15, 01:27 PM
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That tells you the stat is OK. Once you answer PJ"s question we might be able to figure this out.
 
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Old 05-16-15, 01:39 PM
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A few minutes later they both have come back on, run for two or three minutes, and shut down again.
 
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Old 05-16-15, 01:51 PM
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Just to clarify, yes, everything was off and is again. There is no motor noise anywhere, and no air is coming through the ducts.
 
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Old 05-16-15, 02:02 PM
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This one is a little odd. I would expect to see the indoor blower still running.
 
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Old 05-16-15, 02:06 PM
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I'm wondering if your visitor damaged the thermostat cable. Not sure what you mean by wire ducts.
 

Last edited by skaggsje; 05-16-15 at 02:07 PM. Reason: added
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Old 05-16-15, 02:32 PM
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Do you have a VOM- test meter ?

It sounds like there is a problem with the 24vac. Either a transformer problem, transformer overheat or there is a short in the wiring. Usually the transformer is fuse protected and the fuse blows or the transformer itself blows out. I'm trying to figure out what's making the system cycle.

Can you post the make and model of your inside unit ?
 
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Old 05-16-15, 02:56 PM
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skaggsje: Not sure about wire ducts, either. I meant there was no air coming through the A/C air ducts.

A VOM test meter has been on my shopping list for about 30 years. Sounds like it is time I got around to buying one.

The system has come on again. It seemed to run a few minutes longer now that the sun is off the outside unit, but I didn't notice until it was too late to time it.

Thanks to all for your thoughts.
 
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Old 05-16-15, 03:44 PM
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If you have a Harbor Freight nearby, you can pickup an inexpensive digital multimeter such as the one below for under $10. I have several of them that I've gotten for free with coupon, and they work fine for general purpose work.
Digital Multimeter - Save on this 7 Function Digital Multimeter
 
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Old 05-16-15, 04:08 PM
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Thanks, Bob. Will do. (The system says this message has to be over 25 characters.)
 
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Old 05-16-15, 05:06 PM
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It is really strange that an outdoor unit's safety switch could some-how be cutting power to the TR
Is the TR in the condensing unit?
Some units used to have a TR in the furnace & one in the condensing unit.
This is strange; unless somehow the TR is overheating & somehow cutting out.(?)

Does the indoor blower motor have a bad run capacitor?
 
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Old 05-16-15, 06:36 PM
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TR? Sorry. This stuff is all new to me.

I have just put the thermostat back and tried turning the indoor blower to "On" instead of "Auto." Nothing happened. It seems to run fine as long as the outdoor unit is on and shuts off when it does. Something wrong with the indoor blower wouldn't have been my first guess, but what do I know?

Will go into the attic tomorrow morning to find out exactly what is there. Must be a brand and model number somewhere.

Thanks for sticking with this.
 
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Old 05-17-15, 01:38 PM
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Finally made it to the attic. (So much for doing it before the heat built up!)

The unit there is a Goodman model ARU363616BA. The outside portion is a Goodman 65X130361BA.

FWIW, I am beginning to wonder about the clowns who installed it.

They spent five years periodically refilling the coolant before admitting that they knew where the leak was--in the heat exchanger itself, which they claim is not covered by warranty.

My first hint that something was wrong after the raccoon's visit wasn't the heat. It was the water dripping from the ceiling when I woke that morning. Seems he attacked the PVC drain line, or maybe just stepped on it. The installers had neglected to glue a joint, and it came apart, pouring water into my bedroom. Repairing the ceiling took a full 4 x 8 piece of sheetrock, and I still haven't gotten around to some corners that broke open high on the nearby walls.

Now this: Some years ago, after having some post-storm mold killed off and concerned that there might be spores left in the air (something my now-late wife didn't need), we had them install an electrostatic cleaner. We did not notice any change--not sure one would--but still felt that it had been a worthwhile precaution. While up there this morning, I finally realized that they had plugged it into an outlet on the attic light fixture. The light switch also turns the outlets off, as it does on all those ugly ceramic things. So the air cleaner works only when someone is up there trying to fix whatever else is wrong!

[Insert suitably angry rant here.]

Just venting. It's needed.

Thanks for all your help.
 
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Old 05-17-15, 02:06 PM
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No problem on the venting. I'm looking up your unit. Could you have missed a letter in the model number. It looks like it should be ARUF363616BA
 
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Old 05-17-15, 03:44 PM
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Yup. Your version is right.

Can I check the details of the warranty online? Didn't see an obvious page on Goodman's website, but I could have missed it.

Thanks.
 
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Old 05-17-15, 05:55 PM
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Old 05-17-15, 06:13 PM
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Thanks! Very much appreciated.
 
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Old 05-18-15, 02:17 PM
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???

Just giving myself a boost back to the head of the line. Intellicast says it will be in the 90s here by the end of the week, and I'd love to get this resolved before then--without calling in the people who did the installation.

Thanks again to all who have tried to help with this.
 
 

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