My four year old HVAC unit is getting stuck in defrost and I'm constantly having to switch to AC then back to heat so that the unit won't whine in defrost while it's heating.

I had a tech come out to my house to fix it and he deduced that the unit is getting stuck in defrost because something is, "gunking up the valve." I then asked if he would replace the reversing valve to which he replied, "It would put too much pressure on the rest of the system. You need a new system."

Why exactly can't the reversing valve be replaced? In my mind that's like saying, "your alternator is bad. you need a new car." Can someone explain this to me? Clearly there is something that I don't understand.

I found this video on YouTube - https://www.youtube.com/watch?v=k41tRTCHJ3I in which a tech replaces the valve.

A new reversing valve (I looked up the part) costs $125. A new HVAC system will cost $8k. I would happily pay a reasonable amount to have the unit repaired - I know it will be more than $125 obviously.

Edit: Yes, I called five other HVAC companies (on my honor I really did) over the course of the last two weeks trying to find someone that would be willing to perform the repair. Each time I explained what was occurring and how the valve was getting stuck in defrost and would they please replace the valve. Each time I was told, "no". They won't replace it. I needed to purchase a new system.

  • 2
    Please edit your question and remove all the ranting about unethical HVAC tech and so on. None of this is relevant to the question.
    – jwh20
    Commented Nov 21, 2022 at 13:24
  • 3
    Check the Yellow Pages and get another HVAC tech.
    – JACK
    Commented Nov 21, 2022 at 13:57
  • If a tech for company A sabotaged your system, you take company A to court for the damages - which is law, not home improvement. The fact that they have fired the tech could be corroborating evidence, but if the tech was working for them when the system was damaged, they are responsible for the damages (and their insurance can try to go after the tech, but that's not your problem.) So cut that part out of this question and ask it on law.se.
    – Ecnerwal
    Commented Nov 21, 2022 at 14:11
  • 1
    If "something is gunking up the valve", changing the valve won't stop the new one getting gunked up too. You would need to find and remove the source of the gunk. Commented Nov 21, 2022 at 14:12
  • @MartinBonnersupportsMonica - is my question not focused enough? Why can't they just replace the reversing valve instead of the whole system? Along with cleaning my lines and replacing the refrigerant.
    – Anton
    Commented Nov 21, 2022 at 21:30

2 Answers 2


There is absolutely nothing wrong with the question being asked here or with how it is being asked.

To the OP, changing a reversing valve is different than changing an alternator because with an alternator, you just have to remove 1 belt, remove a few bolts, unplug it, and reverse with new part. With replacing a reversing valve, you have to:

  1. Confirm diagnosis (30-60 mins)
  2. Recover all charge (15-20 mins)
  3. Unplug condenser fan/valve and remove top cover (5 mins depending on size)
  4. Set up heat blocking compound or wet cloths (3 mins)
  5. Get your torch situated so that you can unsweat in tight space (3 mins)
  6. Flow nitrogen (5 mins)
  7. Unbraze 4 different connections (max: 1 hour)
  8. Prepare new valve and braze in (max: 3 hours)
  9. Plug fan and valve in and restore top
  10. Sand, cut out, wet rag, and braze in new bidirectional liquid line filter drier, preferably inside the house not outside
  11. Pressure test if needed
  12. Pull an evacuation down to 300 microns, wait 15 minutes, and fail if decays above 500 in that time
  13. Recharge system using SH or SC depending on TXV vs FMD
  14. Probe up and perform comprehensive evaluation on unit

All this work easily takes an entire day.

The reason no one wants to do it isn't for fear of stressing the system, it's just because it's a lot of work that no one wants to do. It's just too much work for too little reward.

Also, no one will want to protect it with a warranty because potential for future problems is too high. If Rev Valve went, other stuff will likely be going to. Correctly diagnosing rev valve is pretty tricky as well, so there's risk you do all that work and you don't solve the problem.

It's too much work and too much risk. It's as simple as that. That's the honest answer you're looking for.

  • Thank you. That's what I thought. I appreciate the honesty.
    – Anton
    Commented Dec 6, 2023 at 14:15

If there is something "gunking up" the reversing valve, and I doubt that there is, I would install suction and discharge filter driers when I replaced the reversing valve. You may have a defective reversing valve or some other problem, possibly a bad control. You said, "I looked up the part and it only costs $125 dollars. OK, I would not even come to your house and ring the door bell for that amount. Looking up the cost of the part has nothing to do with the cost to repair your unit. Get serious with your comments, they do not make a lot of sense. My suggestion, call another HVAC company to see if they can fix the problem or do they concur with the first company.

  • I fully understand that the cost of the repair will exceed $125. I would happily pay several hundred dollars to have the unit fixed. $8k may not be a lot of money for you but it's a heck of a lot of money for me. I'm trying to repair the unit. And I called five different local HVAC companies (I really did). None of them will replace the valve. They all recommend the same thing, "replace the unit". I'm trying to understand why they won't replace the valve.
    – Anton
    Commented Nov 22, 2022 at 15:21
  • "Get serious with your comments, they do not make a lot of sense". This is the truth. I can't make it any more serious. This is what the tech and various other HVAC companies told me.
    – Anton
    Commented Nov 22, 2022 at 15:24
  • @JoustKnight " I'm trying to understand why they won't replace the valve. " Ask them. Commented Nov 22, 2022 at 16:20

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