[Yerfdog]

Hello folks. I could use a little advice.

The heat pump in question is about 7 years old. Only previous trouble was a capacitor last year and some frozen coils a few times.

This last week the a/c had been fine, then we noticed a bit of temperature increase, nothing really drastic. Today, temps outside hit 90, and inside about 87-88. I got home, found the coils free of ice, and cool to the touch. Checked the heat pump - fan runs fine, no compressor.

My initial thought is low charge / leak or compressor. Are there other possibilities?

Thanks!

 

[Doc Holliday]

If you are talking about a low or high pressure switch tripping the unit then the fan itself would not come on as well as the compressor. A low or high tripped pressure switch cuts the entire unit out when concerning a refrigerant (pressure/charge) problem.

Most likely your capacitor is bad, again.

 

[Yerfdog]

Doc, thanks for your response.

I was talking about a pressure switch - thanks for the clarification that it would affect both the fan and compressor. That would appear to rule out a charge.

Last year when the system failed, neither the fan nor the compressor would operate, only the typical hum associated with the failure of the capacitor. Could that capacitor have failed (somewhat, although it looks new - I have not yet put a meter to it), yet still allow the fan to run but not the compressor, when neither could run during the previous failure?

Thanks.

 

[Doc Holliday]

Doc, thanks for your response.

I was talking about a pressure switch - thanks for the clarification that it would affect both the fan and compressor. That would appear to rule out a charge.

Last year when the system failed, neither the fan nor the compressor would operate, only the typical hum associated with the failure of the capacitor. Could that capacitor have failed (somewhat, although it looks new - I have not yet put a meter to it), yet still allow the fan to run but not the compressor, when neither could run during the previous failure?

Thanks.

Certainly, it happens all the time. You have single and dual run capacitors. Single run caps have two sets of three or four prongs, unmarked, run one motor only and look like so:

.

A dual run cap will have three sets of prongs and each set will most likely be marked, fan, c for common and herm for the compressor and will run two motors, the fan and the compressor and look like so:

or be oval. One side running either of the two motors, the fan or the compressor, can go out while the other side is perfectly fine and will run the other motor. Or both can blow at the same time, killing the entire cap.

 

[Yerfdog]

Doc, thanks for your assistance. I changed the d/r cap, and it works again.

Any opinions on the addition of hard start circuitry to ease the load on the cap and help to prevent future failures? I'm considering purchasing a hard start from the same place I got the cap ($40 for the hard start) to assist the cap in compressor startup.

Again, thanks for helping!