Air condition too cold to the point of no air flow

dieseldonato

Veteran Member
Joined
Mar 10, 2023
Location
Us
TDI
2001 jetta
The system absolutely will cycle the compressor, weather for low evap temp or not I don't know. It does kick the compressor off for low and high system pressure to protect the compressor.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Under normal operation these are considered 'non-cycling' compressors. They are variable displacement. The only time the clutch will disengage is if the system is too low on charge or in rare cases the engine controller requests full power and it disengages but on the diesels that hardly ever happens.
 

Stone14

Member
Joined
Oct 24, 2010
Location
Mauritius
TDI
none

As he said, it does NOT cycle off and on. It's always on, but the compressor uses a RCV - refrigerant control valve, to regulate the compressor in producing the correct freon flow;. I am pretty sure the RCV uses the fan setting to modulate this.
Thanks for the help.. can you indicate where is the RCV in the Golf Mk4 please? Is it found in the compressor itself? Or is it the expansion valve?
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
The A4 Golf has a purely mechanical control valve inside the compressor, under the head. The A5 and newer cars use an electronic RCV, and those compressors have no clutch.
 

Stone14

Member
Joined
Oct 24, 2010
Location
Mauritius
TDI
none
Under normal operation these are considered 'non-cycling' compressors. They are variable displacement. The only time the clutch will disengage is if the system is too low on charge or in rare cases the engine controller requests full power and it disengages but on the diesels that hardly ever happens.
Thanks for the reply.. my evaporator is getting below 0 degrees and freezing up.. What can possibly do this? All equipment is OE and I am suspecting the expansion valve to fail! Any advice is welcomed.. Thanks a lot 🙏
 

Stone14

Member
Joined
Oct 24, 2010
Location
Mauritius
TDI
none
The A4 Golf has a purely mechanical control valve inside the compressor, under the head. The A5 and newer cars use an electronic RCV, and those compressors have no clutch.
This being said.. I am thinking more and more about the evaporator expansion valve failing then! Am I right?
 

Stone14

Member
Joined
Oct 24, 2010
Location
Mauritius
TDI
none
If the evap is freezing the most-likely causes are the expansion valve OR it is low on charge. If you KNOW you have the correct charge in the unit (because you put it in there) then its probably the TXV.
I am a complete noob at this.. any idea of the value that mist be charged in the unit? 🤦‍♂️
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Yep and the only way to properly charge automotive systems is by weight. They will run ok down to about half charge, but start to get squirrelly.

One thing to remember is that the refrigerant is the coolant for the compressor, and when you compress a gas it gets VERY HOT. Anything that impedes proper circulation of the refrigerant risks the compressor overheating, the oil will coke inside and once that occurs the damage is progressive and usually terminal. This is also why the fans are critical on these cars; unlike a gas car that will overheat almost immediately without the fans working properly these engines rarely overheat with one or even none of them running. However the A/C compressor will overheat and there is no sensor for that and thus no warning when it does before it is damaged or destroyed.

If you ever completely discharge an auto A/C system (e.g. due to a leak -- its illegal to intentionally vent refrigerant to the atmosphere) you must change the dryer and then immediately pull a hard vacuum before charging it. The chemical in it is one-way, it has little capacity, and any amount of water vapor in the system will react with the refrigerant under heat and pressure to produce an acid which then proceeds to eat everything made out of aluminum (that's most of it, including the evaporator) from the inside out.
 

Stone14

Member
Joined
Oct 24, 2010
Location
Mauritius
TDI
none
Yep and the only way to properly charge automotive systems is by weight. They will run ok down to about half charge, but start to get squirrelly.

One thing to remember is that the refrigerant is the coolant for the compressor, and when you compress a gas it gets VERY HOT. Anything that impedes proper circulation of the refrigerant risks the compressor overheating, the oil will coke inside and once that occurs the damage is progressive and usually terminal. This is also why the fans are critical on these cars; unlike a gas car that will overheat almost immediately without the fans working properly these engines rarely overheat with one or even none of them running. However the A/C compressor will overheat and there is no sensor for that and thus no warning when it does before it is damaged or destroyed.

If you ever completely discharge an auto A/C system (e.g. due to a leak -- its illegal to intentionally vent refrigerant to the atmosphere) you must change the dryer and then immediately pull a hard vacuum before charging it. The chemical in it is one-way, it has little capacity, and any amount of water vapor in the system will react with the refrigerant under heat and pressure to produce an acid which then proceeds to eat everything made out of aluminum (that's most of it, including the evaporator) from the inside out.
Thanks again for the useful information.. one last thing.. the evaporator is supposed to cool down at which temperarure? The expansion valve regulates the evaporator at 6-7 degrees? Right?
 

jokila

Vendor
Joined
Dec 3, 2004
Location
Houston, Texas
TDI
2003 Jetta GLS, Manual
The system absolutely will cycle the compressor, weather for low evap temp or not I don't know. It does kick the compressor off for low and high system pressure to protect the compressor.
True, it's not a totally on system and I wasn't clear, but i meant when the system is turned on by the fan switch there isn't supposed to be a cycling off and on by the compressor.
 
Last edited:

pedroYUL

Top Post Dawg
Joined
Sep 8, 2011
Location
MI, USA
TDI
2015 Passat CVCA; 2015 GSW CRUA; 2012 wagon CJAA; 2004 wagon BEW(brother)
What would the static pressure be at round 17C ambient temp?

Both my 2015 Passat and 2015 Golf Sportwagen were reading a hair below 65 psi, I think they are both low
 

pedroYUL

Top Post Dawg
Joined
Sep 8, 2011
Location
MI, USA
TDI
2015 Passat CVCA; 2015 GSW CRUA; 2012 wagon CJAA; 2004 wagon BEW(brother)
So they weren't low, just then my 3rd car was overcharged at something like 95 psi the same day
 

csstevej

Top Post Dawg
Joined
Aug 12, 2004
Location
north nj
TDI
2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
Why……?
Just get it fixed…..why try to reinvent the wheel….
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
AC service is no game for a newbie. Hope you get it sorted out! Oilhammer is the Man. I've always said once he comments on your issue, you're almost done.
 
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