A3 Jetta Ac freezing up

alanack

Veteran Member
Joined
May 10, 2022
Location
Rhode Island
TDI
1998 Jetta
Lines are freezing up from the compressor to the evaporator.

I replaced the evaporator, heater core, resealed all the stupid blend doors, and the expansion valve.

Is there another metering device in the system somewhere? System is over cooling, and will totally freeze up solid unless it's 2,000 degrees out and the blower is on high.

I'm guessing there's something stuck in the compressor, it's a nissens, year or two old.
 

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Los Angeles
TDI
1997 Jetta TDI (1Z)
As far as I’m aware there is no metering device. I think all the pressure controls are housed in the compressor itself. Maybe your expansion valve is bad?

For what it’s worth, OEM compressors are still available. In fact I’m swapping out the Nissens one I have in my car (perfectly functional) for a made in Japan Sanden model just for peace of mind.
If you’re interested in my old one, feel free to drop me a line.
 

alanack

Veteran Member
Joined
May 10, 2022
Location
Rhode Island
TDI
1998 Jetta
I changed the expansion valve in hopes to fix the problem. Upon removal, I twisted the evaporator and ruined it.

I doubt the new expansion valve is bad too.

I'm going replace the cutout switches on the dryer which I'm confident won't fix anything.
Then I'm going to evacuate it again and put less charge in and see what happens.

I figure the metering device/ controller integral to compressor is stuck open.
 

Shoveltrev

Veteran Member
Joined
Feb 11, 2015
Location
Hutchinson ks
TDI
2002 new beetle deceased, 2003 jetta . 2002 jetta , 2012 sportwagon
had one do this and it had a restriction in the co9ndersor assembly near the outlet leading to the evaporator
 

Shoveltrev

Veteran Member
Joined
Feb 11, 2015
Location
Hutchinson ks
TDI
2002 new beetle deceased, 2003 jetta . 2002 jetta , 2012 sportwagon
the flow control device if equipped in the compressor is mechanical . failure mode usually is undercooling.
 

alanack

Veteran Member
Joined
May 10, 2022
Location
Rhode Island
TDI
1998 Jetta
Hmmmm. I'll have to read up and study the system some more.

Ac is like a meat cooler in this thing even with the fan on high.
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
These have a variable displacement compressor that works in tandem with the valve on the firewall which name escapes me. It's not simply an expansion valve. And yeah, the control in the compressor head can sometimes be the cause of the of system failing and can be changed.

Some searching will splain all this. There's a good sticky in the A4 Forum. Same system. Titled "Radiator/Fan" or something but it covers A/C.
 

alanack

Veteran Member
Joined
May 10, 2022
Location
Rhode Island
TDI
1998 Jetta
These have a variable displacement compressor that works in tandem with the valve on the firewall which name escapes me. It's not simply an expansion valve. And yeah, the control in the compressor head can sometimes be the cause of the of system failing and can be changed.

Some searching will splain all this. There's a good sticky in the A4 Forum. Same system. Titled "Radiator/Fan" or something but it covers A/C.
My fans work on low, however the belt drive fan has bearing noise I think.

Like I said the AC system is over cooling. On a very hot day it's fine, if it's just hot outside the blower needs to be on high to prevent freezing up.

If it's warm out, like running the ac to defogger the widows, or the blower on low, the lines will get ice build up, and eventually the evaporator will turn to a block of ice. It thaws out and leaves a giant puddle under the car.

It has to be the compressor then. What's the go to brand? Nissens has a bad rep on here, and I'm not buying another one.
 

volksguy

Veteran Member
Joined
May 29, 2003
Air conditioner clutch cycle switch it has a long probe that slides in the evaporator fins that will cycle the compressor if it gets to cold.
All so to low of low side pressure will cause lines to freeze up
Caused by ac system needs more Refrigerant
 

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Los Angeles
TDI
1997 Jetta TDI (1Z)
Air conditioner clutch cycle switch it has a long probe that slides in the evaporator fins that will cycle the compressor if it gets to cold.
All so to low of low side pressure will cause lines to freeze up
Caused by ac system needs more Refrigerant
I’ve seen these on other cars, but as far as I’m aware, that’s not a thing on the mk3.
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
You replaced the expansion valve. Was it a name brand? The chinesium versions of these are not well thought of. Even for those parts.

The displacement control in the pump can be replaced. It's a crap shoot but since you're equipped to evacuate and recharge the system it might be worth it. I don't know if it might be your problem.
 

alanack

Veteran Member
Joined
May 10, 2022
Location
Rhode Island
TDI
1998 Jetta
On air conditioner line most time apparently ac compressor is not cycling
Ya that should be here today from id parts...
I don't think it's the issue, but It's worth a shot.

Old school fixed orifice tube systems would cycle the clutch to regulate pressure. Where these cars have a metering device on the firewall and the compressor.
 

alghamedGT

Well-known member
Joined
Dec 10, 2023
Location
MOROCCO
TDI
GOLF MK3 AHU
Yeah ur right i have the same problem
I changed the compressor and the txv because i had weak ac now i have perfect cooling but when i put fan in 2 lines get frozen and the cooling performance get weaker
To not hurt the compressor now i turn fan in 3 and to not get too cold i turn the heater knob slightly its fine untill i find a solution for that problem
 

alghamedGT

Well-known member
Joined
Dec 10, 2023
Location
MOROCCO
TDI
GOLF MK3 AHU
Original one from junk yard i think sanden
Txv is original too from valeo junk yard
Saddly No new parts available in my country 🤦🏻‍♂️
 

volksguy

Veteran Member
Joined
May 29, 2003
As I said too low of a low side pressure will cause freezing up.
What has the high and low side pressure been?
 

alghamedGT

Well-known member
Joined
Dec 10, 2023
Location
MOROCCO
TDI
GOLF MK3 AHU
I dont know in normal use when testing at the shop ac and fan full speed pressure is normal
I get that problem in highway driving when i put the fan speed in 2
 
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