How to Troubleshoot a Faulty High Pressure Cutout on a Residential AC

Follow along with Tim Smith as he walks you through the steps to diagnosing a faulty high-pressure cutout switch (HPCO) on a residential A/C.
Is the thermostat calling for cooling?
Which electrical loads are operating?
Is the indoor fan unit operating?
Is the outdoor fan unit operating?
Is the amperage cycling between 0 amps and 30 amps, or staying at 0 amps?
Is 24VAC measured at the contactor?
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[@viper22304]

Thanks for sharing. Question: how can you measure voltages on the LPCO and HPCO switches if you have the condenser fan motor running? How do you get inside the unit? Thanks

[@AlMaz-y8y]

Thank you.

[@ilovenythismuchilovenewyor5801]

hey Tim how are ya hope all is well. I'm a installer w light service experience. I was testing my own unit at the property where the fan and compressor both would run then cut off. so I tested from the tstat for 24 volts to the condenser I got it contactor also was pulled in but once fed the high voltage by replacing the disconnect fuse back in the cond. fan and compressor would run but then turn on and off. I checked the hv to contact wire (red 6.6 amps) (black 7.6 amps) confirming obviously compressor was getting Juice to it also testing for voltage I got 240 volts coming in. so that part was fine. now testing from the stat wire coming in to where the hp wire connects in series w the lp wire that was connected on the contactor w the stat calling for ac I didn't get 24 volts ... on the digital gauges I see low side 129.6 and high side 129.5 now this is 410a now with the 8.7 slt 75.8 lst 71.6 and the vsat 44.7 and the last 44.6 and sh at 31.1 .....what would you assume the issue is.... low on refrigerant? or faulty low pressure or high pressure switch??

[@0isez]

I have a Lennox heatpump, it was bought about 5 years ago by the previous house owner. When I bought the house about a year ago, I had the unit checked out and the guy said that there was a freon leak that was un-repairable and I needed a new unit for 10 grand! I said I'd think about it but really wanted a second opinion. I ran it anyway and it seemed fine the rest of the summer. Now when I first ran the ac unit it gave me a 413 Lennox error on the screen. I arranged for a different company to come out and take a look at the end of the week. I am hoping that it's a repairable problem. Any comment would be welcome...

[@user-bf5hv9lj7t]

I need automotive fix of a cut high pressure hose on my 2010 Subaru Legacy

[@truedox]

I ended up here because my control board has an error code of 02, which according to the manual is high pressure switch fault. I did not note that the compressor fan is running, so from what you say, the fan not running can cause the high pressure cutout to trip? I tested the capacitor and the microfarad readings are in spec, however there is infinite resistance between fan and common prong. Is that a failed capacitor? Seems odd that it can read microfarads but infinite resistance. The symptoms are that when the heat pump begins to heat, the indoor blower motor and compressor start at the same time, but the compressor (I believe, unless it can be the compressor fan) can be heard stopping after about 2 seconds of running.

[@greenthumb233829]

I would love to know what app you were using to look at all the pieces and can break down everything like that.

[@InterplayLearning]

Absolutely! This is our skilled trades training platform, SkillMill™. If you're interested in using it, you can sign up for a free trial here: www.interplaylearning.com/pricing

[@fishyouall]

Great Video!
I just figured out that my problem is high pressure switch . how do I reset it on old system? I cant locate any buttons. are they resetable? or I need to replace it?
Thanks in advance!

[@InterplayLearning]

The pressure switch needs to be replaced. Something caused it to open. It's possible after replacing it, there may be another problem. Ensure the coil is clean.

[@ejohnfall]

Cool video

[@brtymat5841]

I'm hoping you can guide me in the right direction. I have a Trane heatpump model 4WCX3048A1000AA (on the roof). It is self contained no furnace in the house.
On the heat cycle the unit runs for approx. 30 seconds then shuts off for approx. ten seconds and then back on for the 30 seconds and then back off.
( I believe this is called short cycling). I do not have any problems on the cooling cycle, that works fine. I have replaced the thermostat, blower motor and both caps.
On the reverse valve I can hear the hissing when switching back and forth. (I do this by energizing the reverse valve and then removing the power wire and then re-attaching.
I don't know if this is a correct way of doing it but..) Any guidance would be greatly appreciated.

[@InterplayLearning]

Sounds like it could be cycling at a low pressure or high pressure switch. Could be an indoor air flow problem such as dirty filter dirty blower wheel or dirty A coil.

[@brtymat5841]

@@InterplayLearning Thank you for your reply. Filter was changed, new blower motor and coils were just cleaned within the past 3 months.

[@InterplayLearning]

@@brtymat5841 That's difficult to answer without actually looking at the unit. Reversing valve may be partially stuck.