Diagnosing the stuck HVAC reversing valve 

I just want to take a moment to thank you for doing what you do. I can't even imagine how many people you have helped. The real world knowledge that you give out for free is priceless. I've been in the field for 25 years but was a little weak with heat pumps. We don't really see many of them in Philly. Well, over the past 10 years they've been getting more popular with all of the condos being built. It's cheaper for them to drop heat pumps in than to run gas lines to each unit & set up the gas meters. I think they might be a little lazy too. It used to mostly be people who ran the gas bill up crazy high. But anyway, thanks man. You've helped me out a lot. This video is awesome. I used to feel overwhelmed when on a heat pump service call & hoped the unit was old enough to justify replacement. I can't say I love changing out a 4 way valve, but it's not as bad when you understand them more. It's actually simple now that I'm confident with them. I cut them out & use some couplings, 90s, & Stay Brite though. I've been using Stay Brite a lot since TX valves have become almost standard. I'm lazy & don't feel like doing a nitrogen purge. Thanks Bud 👍😉

The troubleshoot of the RV give a lot of us techs fits, especially when the compressor has failed. As for replacing the RV with the compressor, I blow hot and cold on that one. Many locked rotor failures have no damage to the valve but when you have to tell a customer you have to do most of it all over, you kind of wish you had recommended replacement! Great comments. GFM

The best instructor on line...Period.

thanks. I had the same thing and everyone told me it was not the reversing valve and you told me I was right by watching your video. I love it when I can say I told you so lol

Modern college textbooks teach you to that, whenever a four-way reversing valve is suspected of leaking internally, place your temperature clamps across the low-side line (the indoor coil in the summer or the outdoor coil in the winter) and the permanent suction line between the reversing valve and the compressor. There shouldn't be more than a 3°F difference between them. Also, be sure to take the temperature readings at least 5" away from the valve body, in order to keep the valve body's temperature from affecting your readings. To prevent ambient temperature from affecting your temperature readings, insulate your leads for better accuracy. We love Grayfurnaceman! 🥰🥰🥰 Whoosh! Whoosh! 😆

Enjoyed your vid sir, I'll forward to young contractor friends in the field. Very simple explanation. Beginning my 50th yr in TX. Blessings!

I will be doing a vid on the sman. I used them and the testo as a teacher and I actually liked both of them with some reservations. It can be almost impossible to tell the difference between bad valves or a stuck part way valve in some cases. This one was easy because of the position of the slide. GFM

Great video! I have found many a bad RV with the temperature differential method! Simple but effective! Thank you for sharing!

Must have solid grasp of the mechanics of reversing valves on this. Luckily GFM has provided a whole playlist on heat pumps. Thanks!

Worse part about a bad compressor on a heatpump once you replace it you may have something like this happening.

Always the best videos...Great refreshers and even greater teaching tools...Easy to understand without all the theory that sometimes, is simply, confusing....Is that an oxy moron?...Anyway, I love this mans videos and learn something every time I watch them....Thanks again to the Grayfurnaceman

Wow! Thank you so much. Am new to the tech field and this is gonna help me a lot when I do a diagnosed on this type of units.

You're right! That's why I always recommend the customer pay for a new RV, too.

Thanks for the support. GFM

Thank you! Just went outside & hit mine with a stick! It's blowing cold air now!

El jefe at it again - great video demonstration boss.

You are 💯 right same thing happen to me last week after that I realize that valve is bad…

A partial charge may not have enough pressure to push the valve across. The electric solenoid starts the action but it's assisted all the way across with refrigerant gas pressure, thus the small cap tubes.

It sounds like the valve actuator is leaking by. Check the power to the solenoid. If it is stable and the valve keeps moving, the valve has failed. I would use a clamp meter to be sure there is no problem with the solenoid. Hope this helps. GFM

Its a 1980s York Champion. The unit is used as a mule to test and do vids, so for now, it has been repiped as an air conditioner GFM

Yes, they are great for accuracy, but still keep the analog ones for the dirty jobs! GFM

Thanks. I finally had to get my own. I used to use the school's. GFM

Very helpful and informative!

Thanks. Appreciate your advice. Will kept you posted on the outcome.

New compressor? Man, that compressor looks like you inherited it!

That RV requires very little diagnosis at all. The tricky ones are those losing say 10% gas. Infact a multiple of techs may check the machine without picking the fault. Or think the compressor is on its way out. Temp differential is the best way to pick it generally

thanks so much for sharing all this Videos 👍😁 you Rock

Excellent video. Thank you!!

Thanks GFM

I guess its possible for the discharge to be blocked in the valve and to leak back into the suction. That would explain the high head. Thanks for the video!

Good video...I don't think many who watched got it...if you know what I mean...I did...thanks....

Great video GFM !!! Nice new gauges also !! Take care, Brett

at 2:08 the pressure for the discharge line is 20.4 while for the suction line it shows 257.3

Very clear explanation. Thanks!

Man I love your videos and I love HVAC, there is so much to learn. Can I get some advice from you Mr.Grayfurnaceman? I went to school for HVAC, but I'm starting off doing commercial new construction, I don't mind learning it, but I really want to do service. I'm having trouble finding an hvac service apprentice position, everyone is looking for a minimum of 3 years of experience. How do you think I can get my foot in the door? I have been doing commercial new construction for about a year.

I believe its an E1CP024 Model. The model plate is un readable. GFM

If your discharge gas is leaking back into your true suction line your suction will rise and your discharge will drop. Since the refrigerant is going into the suction line and not the condenser you will not build any head pressure or as much as normal. Yes the suction line temp will rise. I have diagnosed over 30 stuck valves and they fail in two ways: The discharge line is leaking into the suction line. Your suction will rise and your head will drop. This looks like weak compressor valves. Typically the valve will stick in the middle and you will get little to no pressure change. This looks like a compressor that is not pumping at all. I am assuming that is 22 and you said you only had a small charge. I would say you have a clogged or stuck metering device or something.

Will The reversing valve still operate/shift even if you are low on charge?

Very helpful!!

your an awsome old guy, ty for the vid n info

I had a quick question. I think a reversing valve needs at least 50psi to move the internal works from side to side. Wasn't your suction pressure too low to cause the piston to shift? It looks like the small tubes get their pressure strictly from the suction tube in the middle right?

How can you tell the difference between a bad reversing valve or compressor?

Toast R-v, so pilot we assume is working but sleds not moving ?

Excellent video...

This might not be related to a reverse value issue but here is the problem I am having... I have a programmable stat that is set to 74 when I'm at work and 72 when I'm at home. Sometimes, I'll come home and it's 72 but the AC is still running and when I check the temp coming into the house it's around 61. Other times I come home and it's still at 74 and the temp coming into the house is around 71-73. I also notice the large suction line is barely cool and not sweating even around the 61 degree mark. The only way I can fix this issue is shut off the ac, switch to heat mode for about 45-60 seconds, shut off the heat, and switch back to cool mode. This seems to work every time as the temp coming into the house cools down to around 57-58 and the large suction line is close to ice cube cold and sweating a good amount. Now if I just shut off the ac but keep it in cool mode and then turn it back on after the 5 minute system delay, it doesn't solve the problem and 72 degree air continues to run into the house... Would this be a reverse value issue? I thought maybe low on refrigerant but I don't understand how it works just fine when I do the cool,heat, cool switch. If it was low, it shouldn't produce a temp difference of 57 degrees (15-16 degree difference) like nothing is wrong after I do my manual switch... thoughts? After I do this, the system seems to work fine throughout the evening and at night (I continually check the temps coming into the house every time the AC kicks back on the rest of the evening and it hits 58 every time). But something seems to not work right when the program goes to 74 and it can't get cold enough to recover back to 72.

Most likely the problem is that the Teflon in the valve broke and got the valve stuck in that position and at the same time it is blocking the discharge gas resulting in High discharge pressure and High suction pressure. There is no other way a stuck valve will give you such High pressures. If you also add service ports on the other ends other than the middle suction line, the pressures should be way lower than the pressure reading taken from the discharge line as is now. The fast equalization at shutdown will also take place because the suction is not fully blocked in this particular case. I have taken apart many valve and witnessed this problem.

Thanks. I'll try that tommorow and let you know thanks.

brilliant video. thanks!

hey nice video can you do another video on reversing valves

great information

Where can i get the normal suction and discharge pressure for refrigerants. At least the acceptable ranges. Then i will get more from this video. For example i dont know if your discharge of 258psig is off scale and a clear indication of a restriction. It corresponds to a sat temp of 120F which i assume is much too high. Is there an internal relief valve operating in compressor to protect it at this high value ?

Checkout the heat pump playlist. There is another vid about reversing valve operation there. Hope it helps. GFM

hi Gray great video, today I was work on a Trane unit 410A with a reversing & was get the same temp on both condenser & evap line off the valve in cooling , I apply 24v to the sol coil (it was not wire correctly) & it will work for a few them do the same thing again, I'm thing of changing the sol. & the valve, as I think the sol coil is weak & dropping out but why is my temp the same on both lines ? is it not sliding back fully .

Hi. You can't imagine how much you help me to be a better technician. If ever you have time to troubleshoot a TXV valve but, in the outside unit, that would help me too. Maybe you already did. If so, please tell me wich video. Thank you for your good work

So reversing valve receives 24 volts from Tstat to control heat and AC . Then it should move from defrost board in and out also? why is int not moving back to heat if defrost has been satisfied . Pressure differential? Why work way with Tstst but not on its own from defrost ? Thank you .

I have a heat pump and the compressor draws low amps. The name plate says 12 amps and my amp meter reads 4 amps. Does this mean that my compressor is weak? I have good head pressure and suction pressure. The compressor is a scroll compressor from 2010. The air handler is a 2 ton with a fixed metering device and there was a 14 inch flex duct return but I added a return plenum and increased the return duct from 14 inch flex to 16 inch flex duct to reduce the noise in the ductwork. there is one return filter grille that is 20x20.

i like those old york heat pumps

why isn't the pressure in the suction line lower than the discharge line , shouldn't the pressure decrease as it go through the evaporator coils ?

excellent video

you had charging ports close to the compressor to determine the compressor was bad before condemning the RV? That would be tough to diagnose with 2 problems at the same time? was the valves out on the compressor?

Something I'm missing here? Why the high head pressure when much of the discharge is going right into the suction line? In my experience the pressure differences would be small, not super-high head pressure? Symptoms of a worn out compressor is high suction and low head pressures, stuck reversing valves are similar. Please clear this up for me. I'm thinking that the reversing valve is bad, but stuck in AC, but you also have a restriction. Like I said, the pressures shown on your gauges don't add up to a stuck reversing valve, at least this has never happened to me. If have a 15-40psi differential with low current, the real job is to diagnose weather it's the r-valve or compressor. [or both]!

That head pressure definitely in between 256-263. Idk where he got 275 from 🤦🏾‍♂️

Agree, nice video Thanks!

Sr I like your video too much are very interesting. If don't mind I would like to know in Heat Pump in cooling call why suction pressure line is High and discharge line the pressure is low even when the Thermostat and entirely 24 vol control system is ok.Thank you and Regard Sr

I know this video is mostly for experts, but it makes me think I'm getting misdiagnosed on my heat pump hvac. My unit cools fine 95% of the time, but every once in awhile I'll try to cool from our day temp setting of 78 down to 72 and it will struggle to cool off one degree...or it will cool off good at first but then I'll wake up at night and it'll be 79 or so. It's not Summer heat related as most days it cools fine still. I'll play with turning the unit off & on for a few hours or two days...and the problem will usually go away for weeks or months. Pump is good and Puron is full per repairman. He said there was some restriction in the coils & I need new coils. It did seem the system was not cooling properly when he was there. He also quoted for a host of code upgrades like over $100 for the 3 little cap locks on the freon inlets?!? $65 per pound for Puron also seems high. I know you probably can't know for sure w/o gauging, but it seems if coils were bad the cooling would be bad 100% of the time...not 5%. Plus I stood over the compressor one hot day and it seemed cooler air was coming from the top this unit compared to my other unit. Any chance you think this is the reversing valve sticking intermittently? Is that cost high? Thank you!

I have Lennox HP that has blown (shorted 3 R-valve coils (in cooling mode) in the last 2 months, cools great while it's working but the coils shorts out and causes the 24V circuit breaker to blow and then the AC will not work. What could cause the R-valve coil to go bad (short out)? I noticed in your video the R-valve is stuck however the coil is still functioning. Ever had an issue causing the coils to short out? Thank my making such goo videos.

i'm having the same problem with a 410a system, suction line after the reversing valve is hot, when cooling for cool, but both pressures are equalized at 190 psi, is it safe to say, the reserving valve is no good?

and how is it possible that the liquid can flow from higher pressure from the discharge line to lower pressure in the outdoor coil ?

What about section line to hight over 300 psi Little freezing ? Txv locker ? Can you have any Videos for ?

Which model of champion? The only one i've seen is the Champion VI, ( AKA, the tombstone )

how come the pressure going into the compressor from the suction line to the compressor is much higher ( 260 psi) than the pressure coming out of the compressor in the discharge line ( 20.4 psi ) ?

I have same problem my reverse valve is stuck I don’t know how to repair. But my compressor is still good. Any idea please thank you

Will a stuck reversing valve cause the coil to burn up, if so would this happen in a time period of less than an hour

Im working on a heat pump today and using the standard service connections my pressures are within range for 410 but the compressor keeps overheating and cycling off i suspected the rv as it dose everything youve covered in this video EXCEPT quick equalize infact. I watched it during an off cycle and it attempted to equalize but never got close to equal anything i should check or look for ?

In video , discharge temp 170F and pressure 285 psig but sat tem = 127F. Therefore approx 40 F superheat on hot gas discharge. What would normal discharge superheat be on discharge. Thanks for great video, Michael

I had the whoosh but still experienced, hot true suction in heat mode. And true suction freezes in cool mode

Grey man. I have a question. What do I look for if I have a reversing valve cycling in cool then after cycling on it goes into heat. And vice versa. Again it's calling for cooling but sometimes going into heat then back to cool when it wants to. Thanks

it means ok?

The stuck reversing valve does not explain why the discharge pressure is so high. If it is bypassing as shown by the temperatures, the discharge and suction pressure should be closer to the same pressure. Is there a restriction elsewhere in that unit?

You the man

The Differential Pressure Flow Measuring Principle (Orifice-Nozzle-Venturi) see here : diffferential pressure flows from higher pressure to lower pressure

What is happening if it goes cold no problem but when I try to make heat it goes back and forth by itself

Good video you should get rid of that garbage field piece digital manifold and get testos 550's

customer called on heat pump not cooling due to roofer making a hole on the refrigerant line. Repaired line ,pressure test, vacuum system added refrigerant and started up unit and added refrigerant by weight to mfg. specs. and Low side pressures stayed at 20 PSI and High pres. is equalize. What is my next step to find out if its the compressor or reversing valve that is damaged.Thanks

Have you ever used a magnet to see if the valve moves?

GFM, Good Stuff

What's the theory on why the line to the outdoor coil was cooling a bit?

I have freed up stuck RVs before by energizing and denergizing the solenoid or by tapping with the rubber handle of my screwdriver. But that sometimes is not a permanent fix. Have you ever used Supco 88 oil or Renew oil to lube the valve and free it up? I've read really positive reviews on that stuff.

Well some reversing valves, dare i say almost all, use pressure to also move, not just the solenoid.

Thanks

Very nice

Excellent trouble shooting . 8/10/2021

Jeff Daniels is that you?😂

Dont judge me, I am somewhat of a "rookie" especially heat pumps. What are you jumpering from, to the valve?

My heat pump acts funny in ac mode. I have a lennox heat pump 14hpx series. Every few hours it blows warm air even in ac mode. Air is hot enough It will actually raise temp of rooms from 80 to 85. I looked at outdoor unit and when this happens the outside unit fan blows cool air from top. I then change setting in my thermostat (honeywell focus pro th6000). I make fan to 'on' from 'auto' and set the system to cool till 'cool on' sign comes on. Any insight will be appreciated.

Very similar to bad valves on a recip.

Hi. Great video. I have a split level reversible air pump. Upon recently returning from vacation - during which the power cable had been unplugged as recommended - I find that whenever I switch on the unit, the fuse blows. Just before that happens I head a click from the external unit. I am supposing that the trouble is the reversing valve in the external unit. Does this sound correct, from my description? Grateful for someones view on this.

Maybe you can help me. Swapped out a dead compressor to run into similar issue. The suction on the valve gets hot when on ac but when I switch to heat mode the return becomes ambient. Not cold or hot. Also, the service port suction line gets hot on heating and cool on cooling. So it's acting like the valve is moving but not all the way. Is there any way the accumulator can get restricted causing these symptoms?

20 psig is -5F on suction. Is this normal for outside evaporator in heat mode for R22 ?

Last night my ac stopped limbo g cool air. Called a tech to come out today and he ran all his tests and said that I need a new unit or atm east s new condenser. He did nite that the valve did not make the swoosh sound even though the solenoid did move. I’m now more convinced that it’s a bad valve since the compressor does turn on and I’m getting nothing as far as cooling. Now, is there a way to change that valve?