www.tdiclub.com

Economy - Longevity - Performance
The #1 Source of TDI Information on the Web!
Forums Articles Links Meets
Orders TDI Club Cards TDIFest 2016 Gone, but not forgotten VAG-Com List Unit Conversions TDIClub Chat Thank You

Order your TDIClub merchandise and help support TDIClub


Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKV-A5 Golf/Jettas

VW MKV-A5 Golf/Jettas Discussions area for A5/MkV Jetta/Golf (2005/2006 PD and 2009 CR).

Reply
 
Thread Tools
Old March 29th, 2010, 18:27   #1
xracerbob
Veteran Member
 
Join Date: Apr 2006
Location: Hudson Valley, NY
Default A5 Air Conditioning thread

As I intruded on the very informative A4 A/C thread with my questions it was suggested we start one for the A5's. Basically, my AC no workie and I'm trying to figure out why. It appears some of the issues are common to both series of cars (fans), but a lot has changed.

So to review- here are my symptoms- Neither fans operate when tha AC is turned on. I checked the common brush problem with the drivers side and all appears to be good. The clutch is always engaged (apparently this is how this series of compressor works). System pressure was checked- 52 psi low side, same high side with AC on and 45 degree ambient temp. All fuses are good.
xracerbob is offline   Reply With Quote
Old March 29th, 2010, 19:25   #2
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

In this series of AC systems, VCDS is one of your best friends.

By doing the Engine module OUTPUT TESTS, you can check your fan operation.

By going into the HVAC module you can get pressure and control current data, get all kinds of sensor data, and probably do some output tests, too. ( I am guessing at the output tests, as I do not have a model like this to work with.)

This series of compressors has a fairly high failure rate on the electrically controlled compressor displacement control valve.

According to VW you can only replace the compressor, but this might not be the final word.
DanG144 is offline   Reply With Quote
Old March 29th, 2010, 21:42   #3
jetta ,97
 
jetta ,97's Avatar
 
Join Date: Dec 2008
Location: Dallas (McKinney) ,TX ,USA
Fuel Economy: Very good
Default

Quote:
Originally Posted by xracerbob
As I intruded on the very informative A4 A/C thread with my questions it was suggested we start one for the A5's. Basically, my AC no workie and I'm trying to figure out why. It appears some of the issues are common to both series of cars (fans), but a lot has changed.

So to review- here are my symptoms- Neither fans operate when tha AC is turned on. I checked the common brush problem with the drivers side and all appears to be good. The clutch is always engaged (apparently this is how this series of compressor works). System pressure was checked- 52 psi low side, same high side with AC on and 45 degree ambient temp. All fuses are good.
It is to cold to turn a/c. This compressors works different way then old ones. When high pressure start raising then your fan should start working. When high pressure is low fan should not start working.
Wait till get more hotter and check it ,like on 85 F.
__________________
I do any repair on all models,USED/NEW ECU and Cluster swap, Reprogramming Keys , Immobilizer Delete,Cluster LCD Dispay Repair -Clik here
I am trusted TDI Mechanic, VCDS
HEX+CAN
ECU TUNING-TDTUNING Authorized Dealer
MK6 Needle Sweep,MK5 with MK6 Cluster
jetta ,97 is offline   Reply With Quote
Old March 30th, 2010, 01:22   #4
Mach1
 
Join Date: Sep 2005
Location: Spicewood, Tx.
Fuel Economy: 49.3, 48, 21.2,19.99
Default

Defroster should work down to below freezing..

AC compressor will come on when the defroster is energized..


Like Dan said..vag-com is your friend..
__________________
2018 F150 3.5 ECO 3.55 10spd 20s 2tone 26mpg 2turb
2006.5 DE DSG, RC2, Sunroof, 200K miles, 61MPG best
2005.5 Jetta-5 SP LSD Spec S2 130K ELF506 10-30W OCI=20k ORIGINAL CAM RSB Diesel custom 2.5DP/3" SS Pkg 1 Auto-dim mirror auto-WW auto-climate 248tq=150HP RC2 lowered 312 brakes
Mach1 is offline   Reply With Quote
Old March 30th, 2010, 04:25   #5
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

Yeah, at the temperature and pressures specified the AC should not have been interlocked out by either temperature or pressure interlocks.

You only need to be above about 35 degrees to reach the setpoints, and 40 degrees to be reliably above them.
DanG144 is offline   Reply With Quote
Old March 30th, 2010, 05:48   #6
xracerbob
Veteran Member
 
Join Date: Apr 2006
Location: Hudson Valley, NY
Default

I found it it wasn't working on a day when it was mid 70's a couple weeks ago. I have tried the defrost setting as well, and no go. Hope to have it on a vag-com tomorrow.
xracerbob is offline   Reply With Quote
Old March 30th, 2010, 05:54   #7
oilhammer
Certified Volkswagen Nut Vendor
 
oilhammer's Avatar
 
Join Date: Dec 2001
Location: St Louis
Fuel Economy: fantastic
Default

Just to clarify: the A5 has no compressor clutch, they spin all the time. They use a duty-cycled control valve integral with the compressor, controlled by either the fan control module or the ECU (not sure which, Dan will have to chime in here ). However, the ECU should have the actual command portion, just the actual load of the circuit is done via the fan control module.

I would see if the ECU is getting an A/C request in the data blocks first.
__________________
oilhammer
www.cardocautomotive.com
oilhammer is online now   Reply With Quote
Old March 30th, 2010, 07:16   #8
socrates42
Member
 
Join Date: Oct 2009
Location: Boston, MA
Default

i'm just getting a loud psssssstttttt sound when I try my AC. no cold air... Thoughts?
socrates42 is offline   Reply With Quote
Old March 30th, 2010, 08:44   #9
jetta ,97
 
jetta ,97's Avatar
 
Join Date: Dec 2008
Location: Dallas (McKinney) ,TX ,USA
Fuel Economy: Very good
Default

Quote:
Originally Posted by socrates42
i'm just getting a loud psssssstttttt sound when I try my AC. no cold air... Thoughts?
Your freon level is low.Do evac. and recharge.
__________________
I do any repair on all models,USED/NEW ECU and Cluster swap, Reprogramming Keys , Immobilizer Delete,Cluster LCD Dispay Repair -Clik here
I am trusted TDI Mechanic, VCDS
HEX+CAN
ECU TUNING-TDTUNING Authorized Dealer
MK6 Needle Sweep,MK5 with MK6 Cluster
jetta ,97 is offline   Reply With Quote
Old March 30th, 2010, 12:34   #10
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

Quote:
Originally Posted by oilhammer
Just to clarify: the A5 has no compressor clutch, they spin all the time. They use a duty-cycled control valve integral with the compressor, controlled by either the fan control module or the ECU (not sure which, Dan will have to chime in here ). However, the ECU should have the actual command portion, just the actual load of the circuit is done via the fan control module.

I would see if the ECU is getting an A/C request in the data blocks first.
Dead on, Brian.

The high pressure sensor feeds the AC Control Module a pressure signal. The ACCM turns that into a demand current that is sent to the AC Compressor regulator valve. This controls the displacement of the compressor, which in turn raises or lowers discharge pressure.

The Engine Control Module/Unit (ECU) just gives permission to the ACCM to load the compressor at all (this is one of the VCDS OUTPUT TESTs). The ACCM decides how much to load it.

The fans are controlled from the ECU. A signal is sent to the controller built into the large fan. This controls the speed of both fans. The ECU will turn on the fans based on signals from the coolant temperature sensor or the sensor on the radiator, or a request from the ACCM. The Bentley calls this system the "Coolant Fan, 2 speed wth thermal switch" but the speeds are really infinitely variable over a range. (Testing this is another VCDS OUTPUT test.)

Normally you see the fans kick on based on AC system demand after about a minute of operation. To test these fans without VCDS, you need to run the AC system at an idle for about 2 minutes. They should turn on by then. The fans should run together, and at the same speed.
DanG144 is offline   Reply With Quote
Old March 30th, 2010, 14:18   #11
oilhammer
Certified Volkswagen Nut Vendor
 
oilhammer's Avatar
 
Join Date: Dec 2001
Location: St Louis
Fuel Economy: fantastic
Default

Excellent post, thanks! Interesting to fill in the gaps in my working knowledge of the A5's HVAC/cooling fan system.

So ECU requests "air-con", and the ACCM determines the compressor loading via the PWM valve in the compressor, but beyond an on/off request, the ECU is essentially out of the loop on compressor control. I'm sure it probably has some full-load request to the ACCM to back compressor loading off under certain conditions.

Curious, does the ACCM and ECU communicate on the CAN bus or do they have their own dedicated line?
__________________
oilhammer
www.cardocautomotive.com
oilhammer is online now   Reply With Quote
Old March 30th, 2010, 15:55   #12
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

It looks as if the ACCM and the ECU communicate over the CAN bus.

If by PWM valve you mean a Pulse Width Modulation controlled valve, I think that is wrong. I think the valve is simply sent a current/voltage not a pulse width signal. It has been a while but I think the VCDS gives you the control current in a measuring block.

The pressure signal from the high pressure sensor, on the other hand is a PWM or duty cycle signal.

The ECU does all its signalling to the fan control module via dedicated lines, not over the can bus.

I would expect the ECU to forbid compressor loading in high load situations, delay after starting the engine, and probably in overtemperature situations as well. But this is only conjecture.
DanG144 is offline   Reply With Quote
Old March 31st, 2010, 16:30   #13
xracerbob
Veteran Member
 
Join Date: Apr 2006
Location: Hudson Valley, NY
Default

OK- Got my car scanned and here is what came up:

00898-Control circuit a/c compressor
010-open circuit short to plus

So we poke around a little and the connection on the back of the compressor is there but with a slight wiggle comes off in Jason's hand. So no signal is getting to the compressor to do anything. I check with VW and this is an integral part of the compressor and not replaceable seperately. I check with aftermarket A/C parts sellers and they say the same. So its a new compressor for me. I decided to buy a new oem instead of rebuilt ($437.00). The rebuilt was only $75 less, so I decided the difference wasn't worth it. It will be here Friday.

Thanks to Jason (TDIJetta99) for his help and the scan.
xracerbob is offline   Reply With Quote
Old April 1st, 2010, 05:24   #14
oilhammer
Certified Volkswagen Nut Vendor
 
oilhammer's Avatar
 
Join Date: Dec 2001
Location: St Louis
Fuel Economy: fantastic
Default

Great, glad you found it. Just goes to show once again the best first step in diagnosis of any system on a modern automobile is to use a scan tool and exploit the car's own OBD. That's what it is there for!
__________________
oilhammer
www.cardocautomotive.com
oilhammer is online now   Reply With Quote
Old April 1st, 2010, 12:09   #15
funoutdoors121
Veteran Member
 
Join Date: Jun 2008
Location: CT (USA)
TDI(s): 15 GSW S 6MT
Default

Quote:
Originally Posted by DanG144
In this series of AC systems, VCDS is one of your best friends.
By doing the Engine module OUTPUT TESTS, you can check your fan operation.
By going into the HVAC module you can get pressure and control current data, get all kinds of sensor data, and probably do some output tests, too.
Dan, any idea how to use VCDS to get the freon pressure?
I went into the HVAC module, and in Advanced Measuring Values, there are many parameters that can be looked at but I couldn't find the refrigerant pressure.
(I'd like to find out if my system was fully recharged when the condenser was replaced)
Thanks!
__________________
2009 JSW TDI, silver, 6 speed- sold back to VW on 6/13/17
2015 GSW TDI, S, dark grey, 6 speed
VCDS available
funoutdoors121 is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 10:51.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright - TDIClub Online LTD - 2017
Contact Us | Privacy Statement | Forum Rules | Disclaimer
TDIClub Online Ltd (TDIClub.com) is not affiliated with the VWoA or VWAG and is supported by contributions from viewers like you.
1996 - 2017, All Rights Reserved
Page generated in 0.16322 seconds with 10 queries
[Output: 126.19 Kb. compressed to 105.39 Kb. by saving 20.80 Kb. (16.48%)]