Question on 'flushing' an AC system?

[pbm]

We acquired a 2008 Hyundai Sonata 2.4 4 cyl. from a family member with 145K for my daughter. It runs great, burns no oil and I've done the maintenance since my family member acquired it at 56K.(oil, AF, ATF, filters, spark plugs etc...)
I now see that the AC system is blowing warm even though it was ice cold last summer (it sat for a few months). I tried adding R134a but it didn't take it and I saw that the compressor never came on. A friend put his 'computer' on it which showed the compressor was the issue. I ordered pretty much all new parts on RA which were very reasonable due to "Wholesaler closeouts'.
The only parts that I didn't order were the evaporator and hoses (the compressor, condenser, pressure switch, expansion valve, desiccant bag, o-rings will all be changed). When I look at YT videos on flushing they seem pretty complicated. I know I have to have the 'freon' recaptured and then flush the system, install the new parts, vacuum it down and reinstall the freon. Can anybody give me an idea on the best (and simplest way) to flush the existing parts (evaporator and hoses) before doing this job? Thanks in advance for any tips?

 

[Arc]

We acquired a 2008 Hyundai Sonata 2.4 4 cyl. from a family member with 145K for my daughter. It runs great, burns no oil and I've done the maintenance since my family member acquired it at 56K.(oil, AF, ATF, filters, spark plugs etc...)
I now see that the AC system is blowing warm even though it was ice cold last summer (it sat for a few months). I tried adding R134a but it didn't take it and I saw that the compressor never came on. A friend put his 'computer' on it which showed the compressor was the issue. I ordered pretty much all new parts on RA which were very reasonable due to "Wholesaler closeouts'.
The only parts that I didn't order were the evaporator and hoses (the compressor, condenser, pressure switch, expansion valve, desiccant bag, o-rings will all be changed). When I look at YT videos on flushing they seem pretty complicated. I know I have to have the 'freon' recaptured and then flush the system, install the new parts, vacuum it down and reinstall the freon. Can anybody give me an idea on the best (and simplest way) to flush the existing parts (evaporator and hoses) before doing this job? Thanks in advance for any tips?

Sounds like my truck. Every spring it takes two cans of freon because it's leaking. Ive never vacuumed one down even when it's empty and never had any problems.

 

[Mechanician]

Flushing lines works - pretty straight forward with a solvent designed for that - with compressed air. I see a flush kit available on AZ.
Flushing the evaporator - not so much. It is almost always a failure, due to the fact - the tubes run in parallel internally.
In other terms - it's not a single pipe that runs from the inlet, to the outlet.
The solvent and air will find the tubes that are the least clogged, and all flow through those, without touching the worst ones.
A flush may not be needed though, I've seen many that were never contaminated from a compressor failure.
It can be checked using Q-tips, inserted and wiped around both the inlet and outlet. If the tip stays pure white, you're good to go.
You can check the entire system in that manner. Sometimes the contamination flows into only the low side, or only the high side.
Worst case for the evaporator is when it blows backwards, into the outlet.
If the evaporator is contaminated, you would be gambling all your money spent on the other parts, trying to flush it.

 

[pbm]

Sounds like my truck. Every spring it takes two cans of freon because it's leaking. Ive never vacuumed one down even when it's empty and never had any problems.

A few years ago I replaced a condenser on a different Hyundai that my (other) daughter crashed and all went. I got the vacuum, gauges etc...from the AZ "loaner tool' program. This experience gave me the 'testicular fortitude' to attempt this job. I've read that doing the job without 'flushing the system' will compromise the new compressor (metal particles etc...) which is why I ask for a simple way to flush the parts that won't get changed....

 

[wag123]

Recommendation... It is always a good idea to install a high-side inline filter after a compressor failure replacement.

 

[Nukeman7]

We acquired a 2008 Hyundai Sonata 2.4 4 cyl. from a family member with 145K for my daughter. It runs great, burns no oil and I've done the maintenance since my family member acquired it at 56K.(oil, AF, ATF, filters, spark plugs etc...)
I now see that the AC system is blowing warm even though it was ice cold last summer (it sat for a few months). I tried adding R134a but it didn't take it and I saw that the compressor never came on. A friend put his 'computer' on it which showed the compressor was the issue.

A few basic questions: (1) What were the high and low side refrigerant pressures on the non-operating system? (2) How did your friend determine with his "computer" (I assume diagnostic scanner) that the compressor had failed? A diagnostic tablet can only test/activate electrical components. If the compressor clutch is burned out, it will say the solution is to replace the compressor. IME, it is very possible/probable that the A/C compressor clutch has failed or the clutch air gap is excessive, thus preventing the compressor from engaging. I would highly encourage you to eliminate this possibility before opening up the sealed system and replacing parts unnecessarily. Replacing a compressor clutch is relatively inexpensive and non-invasive to the sealed system.

I ordered pretty much all new parts on RA which were very reasonable due to "Wholesaler closeouts'.
The only parts that I didn't order were the evaporator and hoses (the compressor, condenser, pressure switch, expansion valve, desiccant bag, o-rings will all be changed). When I look at YT videos on flushing they seem pretty complicated. I know I have to have the 'freon' recaptured and then flush the system, install the new parts, vacuum it down and reinstall the freon. Can anybody give me an idea on the best (and simplest way) to flush the existing parts (evaporator and hoses) before doing this job? Thanks in advance for any tips?

If the compressor did not catastrophically fail internally and send debris throughout the system, flushing is not needed. You must have a complete diagnosis and understanding of the mode of failure before starting any repairs. Opening a sealed system and replacing good parts is a recipe for disaster in an A/C system. It would be akin to performing a knee replacement on a patient because he complained about joint pain...but he didn't disclose that he twisted his knee playing pickleball last week.

 

[pbm]

A few basic questions: (1) What were the high and low side refrigerant pressures on the non-operating system? (2) How did your friend determine with his "computer" (I assume diagnostic scanner) that the compressor had failed? A diagnostic tablet can only test/activate electrical components. If the compressor clutch is burned out, it will say the solution is to replace the compressor. IME, it is very possible/probable that the A/C compressor clutch has failed or the clutch air gap is excessive, thus preventing the compressor from engaging. I would highly encourage you to eliminate this possibility before opening up the sealed system and replacing parts unnecessarily. Replacing a compressor clutch is relatively inexpensive and non-invasive to the sealed system.

If the compressor did not catastrophically fail internally and send debris throughout the system, flushing is not needed. Before attempting any repairs, you must have a complete diagnosis and understanding of the mode of failure before starting any repairs. Opening a sealed system and replacing good parts is a recipe for disaster in an A/C system. It would be akin to performing a knee replacement on a patient because he complained about joint pain...but he didn't disclose that he twisted his knee playing pickleball last week.

I tried pushing the clutch in manually and I also tried jumping the 'pressure switch' ....both to no avail. I purchased all the parts for about the same price (or less) that a shop would charge for much less (less than $350). I don't mind replacing parts on a 17 year old system as long as I don't hurt them with debris from the remaining parts. As I stated earlier, the AC was ice cold last summer and after sitting for months the compressor won't kick on....if I can run solvent/compressed air and clean out the system to get a few years out of this otherwise good running car...I'm good with that. I'm just looking for info on the best way to 'flush' the hoses and evaporator without needing an engineering degree?
PS: When I tried installing freon the gauge on the can read 'high'....beyond that IDK the pressures because I haven't 'borrowed' gauges yet.

 

[brages]

I have flushed with the AutoZone kit before. I think it worked fine, car got totaled a few months later so I will never really know, lol

 

[brages]

I wouldn't bother flushing anything if it's just that the clutch on the compressor is bad. Which seems to be what your LIMITED troubleshooting is suggesting.

 

[Chris142]

If the compressor locked up you have to open everything up and flush. If it just had a clutch failure no reason to flush. Did it lock up? Clutch failure is very common on those cars

 

[Hohn]

Recommendation... It is always a good idea to install a high-side inline filter after a compressor failure replacement.

This could be a good idea, although I have no idea what the specs for such would be.

 

[Hohn]

We acquired a 2008 Hyundai Sonata 2.4 4 cyl. from a family member with 145K for my daughter. It runs great, burns no oil and I've done the maintenance since my family member acquired it at 56K.(oil, AF, ATF, filters, spark plugs etc...)
I now see that the AC system is blowing warm even though it was ice cold last summer (it sat for a few months). I tried adding R134a but it didn't take it and I saw that the compressor never came on. A friend put his 'computer' on it which showed the compressor was the issue. I ordered pretty much all new parts on RA which were very reasonable due to "Wholesaler closeouts'.
The only parts that I didn't order were the evaporator and hoses (the compressor, condenser, pressure switch, expansion valve, desiccant bag, o-rings will all be changed). When I look at YT videos on flushing they seem pretty complicated. I know I have to have the 'freon' recaptured and then flush the system, install the new parts, vacuum it down and reinstall the freon. Can anybody give me an idea on the best (and simplest way) to flush the existing parts (evaporator and hoses) before doing this job? Thanks in advance for any tips?

While I’m fortunate enough to own LOTS of tools and have pretty extensive DiY capability for a guy with no lift, I definitely leave A/C work to my local shop.

 

[Nukeman7]

I tried pushing the clutch in manually and I also tried jumping the 'pressure switch' ....both to no avail.

If you understand basic electrical circuits, I suggest that you look at the wiring pigtail that feeds the electromagnet on your A/C compressor clutch. With the engine off, disconnect the wiring plug and momentarily jumper 12 volts from the battery to the clutch electromagnetic coil. If the clutch doesn't engage, either the coil is burned out or the air gap is excessive. If the clutch does engage, there is a problem with the A/C control circuit (e.g., bad relay, blown fuse, open wiring circuit, etc.).

I purchased all the parts for about the same price (or less) that a shop would charge for much less (less than $350). I don't mind replacing parts on a 17 year old system as long as I don't hurt them with debris from the remaining parts.

The concern is not cost or age of the OEM parts. It is the inherent risk of inducing additional/future leaks on a system that may not be compromised. Decades of automotive repair experience has shown me that a factory sealed and charged A/C system will be more leak-free and trouble free than the same system once its integrity has been compromised and repaired.

As I stated earlier, the AC was ice cold last summer and after sitting for months the compressor won't kick on....if I can run solvent/compressed air and clean out the system to get a few years out of this otherwise good running car...I'm good with that. I'm just looking for info on the best way to 'flush' the hoses and evaporator without needing an engineering degree?
PS: When I tried installing freon the gauge on the can read 'high'....beyond that IDK the pressures because I haven't 'borrowed' gauges yet.

If it reads "high" without the compressor engaging, the likelihood is that the system is completely leak free at this point. I implore you not to breach this system unless you definitively know the compressor has failed internally. When the compressor seals fail internally, the clutch will engage and the compressor will spin; however, the refrigerant pressures will not change significantly on either the high pressure side or low suction side.

 

[38Chevy454]

Can you turn the compressor by hand? Not the clutch, but the compressor. Is it locked up? Or is just the clutch not engaging? Have you tried testing the clutch with an ohmmeter? Try jumping the pressure switch to see if the compressor kicks on? Put gauges on and see what static pressure is, if any? Lot of easy diagnostic that you can do to get a better determination of what is actually not working.

Just seems a lot of unknown to tell you what needs to be done. But since you have all the parts, if you do open the system up then a flush is pretty easy as the basic process is a solvent that you put in and then blow out. Vacuum will boil off any remaining solvent. Don;t forget you need to add oil back in if you do the flush as it is intended to remove the old oil plus any other contaminants. Speaking of that, if the compressor did lock up, you will have the system contaminated with compressor shavings or whatever as it destructed before it locked up.

 

[pbm]

I'm not knowledgeable enough to get deep into why the compressor won't 'kick on'. I do believe the system is full and I tried to 'jump' the compressor with a paper clip at the pressure switch with no luck.

At this point I'm going to replace the parts that I've already purchased and hope for the best. My question is...how do I 'flush the system' (evaporator and hoses) as simply as possible. At the end of the day it's an old car and if I blew $350 ....I'll accept that. If it get's through the summer with cold A/C I'll take it from there....probably sell it to someone who can fix it and have a decent running car cheap.

PS: The compressor RA sent as a 'famous brand' (Carquest) for $125 ... is (Carquest DW67348) which on the AA website is $448 and has a 5 star rating so no matter how it goes I didn't get burned as bad as it could have been.

 

[brages]

Frustrating!!

 

[el Nuke]

I'm not knowledgeable enough to get deep into why the compressor won't 'kick on'. I do believe the system is full and I tried to 'jump' the compressor with a paper clip at the pressure switch with no luck.

At this point I'm going to replace the parts that I've already purchased and hope for the best. My question is...how do I 'flush the system' (evaporator and hoses) as simply as possible. At the end of the day it's an old car and if I blew $350 ....I'll accept that. If it get's through the summer with cold A/C I'll take it from there....probably sell it to someone who can fix it and have a decent running car cheap.

PS: The compressor RA sent as a 'famous brand' (Carquest) for $125 ... is (Carquest DW67348) which on the AA website is $448 and has a 5 star rating so no matter how it goes I didn't get burned as bad as it could have been.

Do you have an air compressor at your disposal for use in the flushing process?

If not, I say skip the flush idea altogether and let it ride.

 

[Mechanician]

I'm not knowledgeable enough to get deep into why the compressor won't 'kick on'. I do believe the system is full and I tried to 'jump' the compressor with a paper clip at the pressure switch with no luck.

At this point I'm going to replace the parts that I've already purchased and hope for the best. My question is...how do I 'flush the system' (evaporator and hoses) as simply as possible. At the end of the day it's an old car and if I blew $350 ....I'll accept that. If it get's through the summer with cold A/C I'll take it from there....probably sell it to someone who can fix it and have a decent running car cheap.

PS: The compressor RA sent as a 'famous brand' (Carquest) for $125 ... is (Carquest DW67348) which on the AA website is $448 and has a 5 star rating so no matter how it goes I didn't get burned as bad as it could have been.

The simplest way is to disconnect the lines at each end and blow solvent through them, from whichever end you can reach / get at.
Don't leave stuff hooked up, and try to flush the "system". That isn't the simple way.
You're going to have most everything apart already if you install all the parts you listed anyway.
I already stated why trying to flush the evaporator is a poor idea.
Picture 10-12 tubes laying side by side, and trying to flush them all at once. It doesn't happen.

 

[troymcclure]

While I’m fortunate enough to own LOTS of tools and have pretty extensive DiY capability for a guy with no lift, I definitely leave A/C work to my local shop.

Me too. I mean it’s getting to the point where some shops are even subcontracting it to AC specialists. One of my cars kept freezing up the evaporator and it wasn’t a straightforward issue. After a Honda dealer and a reputable indy couldn’t fix it, it made me realize how much expertise there is to be had in auto HVAC diagnosis that is beyond the scope of a general mechanic. In the Bay Area there’s an AC savant that many very reputable shops farm their AC work to. I finally took it to one that he worked at and he nailed it.

 

[Mechanician]

Me too. I mean it’s getting to the point where some shops are even subcontracting it to AC specialists. One of my cars kept freezing up the evaporator and it wasn’t a straightforward issue. After a Honda dealer and a reputable indy couldn’t fix it, it made me realize how much expertise there is to be had in auto HVAC diagnosis that is beyond the scope of a general mechanic. In the Bay Area there’s an AC savant that many very reputable shops farm their AC work to. I finally took it to one that he worked at and he nailed it.

It's sad that it's gotten to that point in some areas. I worked in Florida for 3 decades, and can't imagine what it would be like if there were a limited number of reliable A/C shops.
Every car's A/C runs pretty much whenever the car is running - year round there. Lots of repairs to be done!