Hyundai Getz aircon troubles - and a possible solution

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Downunder35m
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Re: Hyundai Getz aircon troubles - and a possible solution

Post by Downunder35m »

After all this trouble that dragged out far too long, what is the conclusion?

While the condenser is just on the limit in size and capacity for a hot Aussie summer day, the evaporator is not.
At least not in terms of being able to provide enough cooling once the inside got to baking temps while being parked somewhere.
After about 10 to 15 minutes the cabin reaches and acceptable air temps if you have the outlets blowing at you but that's about it.
You need at least another 30 minutes for the interior to cool down accordingly and if the sun is still out this dashboard will stay hot.
It is not as much a matter of evaporator volume as it is a matter of physical size.
A small block with multiple layers of coils.
Works great for a small portable fridge but not so much for a car.
The idea is that air comes in from one side and the refrigerant from the other.
Resulting in the air getting progressively colder while passing through.
Problem is that with the air speed for such a tiny core there just isn't enough time to absorb enough heat.
So while the core gets colder and colder the air going through won't be able to to release enough heat to the core.
Hence the owners manual stating to always use the aircon with the blower on full....

Some creative people in other hot parts of the world "fixed" the problem by installing a fan / motor providing a much higher airflow rate.
Keeping the core above freezing temps and system pressures on a hot day acceptable.
But as you already guessed: If it gets too hot the clutch disengages because now our system pressures are getting totally out of whack.
However: There seems to be a possible solution.
TXV hack to electrical....
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
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Re: Hyundai Getz aircon troubles - and a possible solution

Post by Downunder35m »

Hacking a TXV is not for anyone scared of breaking things or unable to replace one....
And of course it nothing anyone should recommend....
At least not for use in a car.
So check my threat on TXV hacking if you want to refurbish some old room aircon or freezer ;)
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
Downunder35m
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Posts: 1057
Joined: Sun Aug 16, 2020 5:32 am
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Re: Hyundai Getz aircon troubles - and a possible solution

Post by Downunder35m »

I now had a few days where I could justify using the aircon and it is still going strong.
On a 32° day with the interior warmed up to about 48 degrees C it takes about 8 to 10 minutes to reach a cozy temp with the blower on 3.
From there it is enough to set the blower to 2 unless the sun is still blasting.
Takes around 15 minutes for the aircon to blow out the vent wit a temp below the 8°C mark.
Which brings the system back into the lower temp ball park these aircons were capable of when still new.

So how COULD you spot a (partially) blocked condenser in your car?
A FLIR can might be an option but as the core quickly gets to an even temp it only works right when you switch the aircon on.
And with the system still building up to normal operation conditions it would be a hit and miss.
The only real indicator of trouble is this bag for the desiccant.
Which of course means evacuating the system and taking the bag out.
The thing is in there to absorb moisture but you might wonder why it is so damn big....
The old bloke fixing the aircon explained that this bag collects moisture on the INSIDE but that the bag material itself acts like a filter.
In a good and clean system such a bag looks reasonable.
A bit of discoloration here and here but nothing major.
If the compressor does over time, the system had a leak or there is excessive wear on the compressor the oil will show.
And that oil ultimately lands in the dryer bag.
So if your bag comes out more black than white, has a REALLY bad smell (not like hydraulic oil, more pungent and unpleasant) than chances are the oil got fried.
The black is carbon from the breakdown and fine metal dust from the compressor.

The good news is that those compressors can tolerate a lot of abuse!
As long as they still pull half decent vacuum and pump to over 200PSI you can just keep them running.
The best option for a filthy dryer bad though is to not only replace the bad and start over.
Take the condenser AND the compressor out - have new rings at hand to replace the old ones.
Empty both of as much oil as you can - don't forget to measure the amount....
Check what sort of oil you need, in most cases it will be a PEG oil.
Fill back with fresh oil or oil- dye mix what you took out plus an extra of about 15ml for the old dryer bag.

Why replace the oil?
Obviously filthy oil won't perform....
For us however it means our new dryer bag would quickly fail again thanks to the remaining crap oil in the system.
The lubrication isn't great either, especially if you already found metal residue in the goo and gunk that came out.
Fresh oil really revives the system and keeps it running for quite some time to come, making it well worth the extra work and swearing ;)

Ok, what's the plan then to improve on the cooling?
On R600 one problem is the pressures and lower amount of refrigerant in the system.
The first is easy to fix by adding a little splash or R290.
Unlike your aircon at home in your car the compressor constantly changes speed.
Making the TX valve the working horse.
As in our Getz we won't have a variable displacement compressor the TX valve has to handle quite some amounts at higher REV's.
While below the 1500 RPM mark the cooling is a bit compromised as there simply isn't enough refrigerant being pumped through.
The system should operate PROPERLY once the evaporator core is cooled down to operating temps - SHOULD!
In a proper car, at this stage, the compressor would start to cycle, rather keeping the core at a low enough temp then risking to freeze it over.
But it seems the required temp sensor for checking the correct temp is either located in a bad spot or the response far too quick.
With R600 running through it the boiling temp is quite a bit lower and results in a faster cooling down.
On the other hand that means the low pressure must be kept high enough to prevent the R600 going through as a liquid - we want to boil it all off well before any liquid goes back to the line.
If it does go back into the outlet line you will see the TX freeze over quickly and your pressures going bonkus as the refrigerants starts to accumulate in your evaporator.
The thing that Hyundai did wrong in the Getz and some other models is the compressor control!

I now had enough time to observe a WORKING system with a properly metering TX valve.
Well, the later based on the temp of what comes out of the evaporator only, not based on the actual flow rates required - keep that in mind...
Once the core is cold enough so the outcoming refrigerant will cause the TX vlave to close a bit it also increases the system pressure.
No surprise really as this is how it works....
Especially on the low side you will notice these pressure fluctuations if you have proper gauges attached.
But you see even bigger changes by changing the RPM's.
And that the problem we seem to face!
Once the temp control disengages the clutch it should stay OFF until the core temp is ABOVE the set temp again.
Like in a fridge there should be a destinct delay - to prevent the compressor from engaging while the system is still equalising!
Hyundai though decided that once the pressures are acceptable enough the compressor shall turn on again - without checking the temp sensor.
And after a rather short run the temp sensor again complains and shuts it all down.
Why is that a problem you ask?
The core does not get enough time to warm up again....
I suspect they placed the temp sensor somewhere near the outlet instead of having it near the inlet.
With the core still below acceptable temps the refrigerant won't boil off as quickly and more liquid will go deeper into the core - further upsetting the temp sensor.
Ultimate result is that sooner on a cool day, later on a hot day the system pressure will go too low as too much refrigerant stays in the evaporator.
Of course it is next to impossible to relocate the temp sensor without major surgery on the dash board.....

The easiest fix seems to be to just use more R290 to increase the overall boiling point through a higher system pressure.
Which would bring us back to how the darn thing would work on R134a to begin with - below any acceptable levels LOL
Another option would be to change the way the pressure sensors supply data.
We won't do that because the ECU would then mess things up even further.
If we could tap into the temp sensor, or just add two new ones to check air inlet temp and core temp we could just bypass the original control system.
Add a little Arduino and you get a full climate control in return that further reduces the fuel consumption when the aircon is running.
Just a total pain to bypass all the wiring and splice in new ones going to the dash :(
Exploring the works of the old inventors, mixng them up with a modern touch.
To tinker and create means to be alive.
Bringing the long lost back means history comes alive again.
liquidhandwash
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Re: Hyundai Getz aircon troubles - and a possible solution

Post by liquidhandwash »

Some good info there, great work downunder. Maybe you can find a Hyundai at a wrecker with the dash out so you can see where the temp sensor is or how hard it would be to relocate it. Even better leave the old one in place and put the wrecker sensor anywhere you want.
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