Heat pump failure: Compressor or Reversing Valve?


Old 01-18-08, 03:40 PM
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Heat pump failure: Compressor or Reversing Valve?

Hello all. I'm hoping you can shed some light on this issue; I'm not sure who to believe between two techs.

My heat pump quit working. Compressor will start but shut down shortly thereafter. Fan on the condenser unit and inside blower continue to run.

Tech A says it's a bad reversing valve: No temp difference between discharge & suction lines in or out of reversing valve. Manually tried to switch valve--valve is clicking but not switching.

Had Tech B give a second opinion. He said it's a bad compressor. Says reversing valve can either fail by sticking in heat mode, cool mode, or between (bi-flow) but in all three cases if the compressor is working then when you start it there should be a change in coolant pressure. He showed me the gauges and there is no change when the compressor starts. He interprets the clicking of the valve to mean it's switching.

To this Tech A says, no, in the bi-flow situation there will be no pressure change when you start the compressor, and if the compressor were bad you'd hear metalic sounds.

Needless to say, I'm confused. Who should I believe?


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Old 01-18-08, 09:11 PM
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Compressors shut-down shortly after attempting to start when there is an internal short. I would agree with the Tech that condemned the compressor. A metallic noise would indicate a mechanical failure...but there are electrical failures as well, which produce no sounds other than the tripping of a fuse/circuit breaker)

But you can test this...If you happen to have an ohmmeter, turn power OFF at the outdoor unit, remove the service door, reach in for the compressor terminal cover and remove it. Then disconnect the three wires connecting to each one of the compressor's 3 terminals (let's arbitrarily call them A, B and C).

Touch with each meter lead two of the terminals (since the compressor has 3 terminals, you'll do this 3 times, each with a distinct pair of terminals...say terminals A-B, B-C and A-C)
You should get 3 different readings...small readings but readings nevertheless.
- if when testing any given pair the meter reads "0" or "infinity", the compressor is dead (0=shorted winding; infinity= open circuit)

Now touch with one of the meter leads any unpainted metal part of the unit, and with the other, in succession, terminals A, B & C. If the meter reads "0", compressor in dead (short to ground)
Old 01-19-08, 07:18 AM
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Hmmm tech A and Tech B then huh. Amateurs maybe?, is this maybe Brother in law A and maybe Father in law B? LOL. Do the exact test that the previous poster told you to and post back results this should be easy to resolve. I was recently helping a friend repair his MVAC on his Yukon he had just bought himself a nice new set of R134A guages. So he pops them on and man no change in pressures at all condemned the compressor within 5 seconds flat. Now I asked him about the odd shape of the hose ends and it turns out that they are valved on the end and he never opened up the valves on the end of the hoses duh huh lol. Be careful when dealing with amateurs
Old 01-20-08, 12:39 PM
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Like said If A didnt ohm the compressor and B didnt ohm out the compressor. Id sure call the next TECH - C guy to see what he finds. If a small short might get by with a good start kit with a potential relay in it.
Old 10-10-10, 05:26 PM
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I have this same problem with a heat pump as steave do what was wrong with the conderser unit....
Old 10-10-10, 07:38 PM
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If the system is older than 10 years I'd replace the unit. So u will not need to no
Old 10-11-10, 08:27 AM
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I don't know what's the brand of your heat pumps. While, there should appear "failure code" on the control panel of the heat pump when something goes wrong. You can find the explain and solution for the "failure code"---listed by the manufacturer on the manual. At least our air-water heat pump water heaters do so.

So we should choice a brand which can provide after-sale cooperation, and, which is a mature brand.

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Old 04-25-11, 04:10 PM
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If you havent disconnected or removed the unit I had a instance where the drier was clogged and the unit wouldn't measure a increase in pressure, and by feeling the temp of the freon brefore and after the drier, it could be that the drier or driers are clogged.
Old 04-28-11, 06:14 PM
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Originally Posted by sheetman52 View Post
If you havent disconnected or removed the unit I had a instance where the drier was clogged and the unit wouldn't measure a increase in pressure, and by feeling the temp of the freon brefore and after the drier, it could be that the drier or driers are clogged.

FIY, the post was started in '08. no point of waking up the dead/old post.

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