DIY Home Improvement Forum banner

Exterior heatpump unit shuts off randomly

279 Views 11 Replies 2 Participants Last post by  roughneck
I had this issue with my previous old unit and this one that was installed approx 3 years ago.

This is a heatpump system and I have the issue in heat or cool mode and have replaced the thermostat.

Randomly the outside unit will not power on (or shuts off while running, not sure which). I discover the issue because the fan is running without it getting any warmer (in winter) or cooler (in summer). I have 2 double breakers for the system and neither will be tripped. I can turn off the thermostat and both breakers for a couple mins, then turn them both back on and set the thermostat and it works again.

Some research I have done may indicate I need a hard start capacitor. Or, that the the system may be overheating due to not enough airflow due to closed off vents etc.

I do have a couple vents closed off but seem to have a lot of airflow through the many other vents I have. Filter is changed regularly. One other thing of note is that my house is about 40 years old and on a slab. One company that I got a quote for when replacing the unit mentioned that they may need to run new tubing through the attic as the tubing going through the slab is too small for a modern system. The company that ended up replacing it didn't think it was an issue but did have to use a reducer on the lines.

So, I am thinking of replacing the breakers for good measure and then consider a hard start cap (they are cheap enough). Other than that, any suggestions on what the cause is or how to try to track down the cause?

1 - 6 of 12 Posts
The air handler is a lennox CBX25UH-030 and the external unit a 14HPX-030-230.

Do you mean look at the board on the external unit for a code on the diagnostic leds?

It just seems strange that I am having the same issue with the new unit that the old unit had. This is why I am thinking of a power or tubing restriction issue. BTW, it wasn't replaced for this issue. The compressor failed on the old unit. It was really old BTW. Like 25 years or so.


See less See more
Thanks but not familiar with the term "active call" and my google-fu hasn't helped :) I assume you mean look at the diagnostic LEDS?
Not yet. It hasn't shut off again.
So It happened yesterday. Had power at the outside unit and the diagnostic LEDs indicated "High Pressure Switch Lockout". I have read up on the possible causes and nothing jumps out. I plan on cleaning the outside coils (the unit has plenty of open area, nothing blocking airflow) and checking the vent tubes in the attic to make sure there are none that are collapsed and will open up a couple vents I have closed. I will also test the start capacitor. Filter is changed regularly.

Any other suggestions?
Ok, so is the cause the fact that there is not enough heat transferred from the refrigerant before it goes back to the outside unit? Like not enough airflow (dirty coils, slow fan speed etc?)
1 - 6 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.