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 MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

Reply
 
Thread Tools
Old May 29th, 2009, 10:30   #1
mk3
Veteran Member
 
mk3's Avatar
 
Join Date: Sep 2005
Location: Wisconsin, USA
Fuel Economy: 46.4 lifetime
Default AC warm air, but compressor and fans DO run

I do have the troubleshooting guide from DanG144 - thanks!

I know there are many threads on this topic, but I haven't seen one with my issue.

My wife noticed and then I confirmed this spring that the A/C is not working. When compared with our 01 Passat it becomes quite clear.

03 Jetta with Manual A/C.

G65 showed 22.3% duty cycle measured in a mid-70ish day, measured with Fluke.

Both fans turn on when I turn on the AC

The clutch engages and spins - I checked it last night.

I moved the heater control knob during a trip and it changes from Hot to ambient so the flap would seem to be working.

- What else can I try? It seems like everything is OK except no cold air comes out? I was considering trying to measure the temperature of the hoses with an IR gun and compare my Passat to the Jetta.
__________________
03 Jetta TDI 5-spd 320k mi PP520 Nozzles, IQ 5.8
13 Prius 135k mi
16 Civic 1.5L turbo (30k mi) ~ 37 mpg
mk3 is offline   Reply With Quote
Old May 29th, 2009, 10:47   #2
compu_85
Gadget Guy
 
compu_85's Avatar
 
Join Date: Sep 2003
Location: Springfield VA
Fuel Economy: 3.3 Mi/kWh
Default

What's G65?

You need to look at the pressure levels in the system.

-Jason
__________________
Present:
2018 Tesla Model 3 DM. 50,000 miles.
2014 Cadillac ELR. 38,000 miles.
2013 Fiat 500e. 32,000 miles.
1991 Mercedes 350SDL 230,000 miles, 70,000 on engine. 18/27 MPG.
Past:
99.5 Jetta "GLX" TDI. 323,000 miles. Power Memory Seats, HIDs 11mm pump, BV39 Turbo, RCIII 36/47 MPG. Sold to JDSwann's Brother.
2012 Passat SE TDI DSG. 114,000 miles. LED tails, Memory Seat, HIDs. Bought back by VW.
2004 Touareg V10 TDI. 165,000 miles. Sold to Matt98AHU w/ flat camshafts.
1988 Audi 5000S Quattro, 1992 Jetta ECOdiesel, 1991 Jetta ECOdiesel.
Thank you for giving me the BUG*PWR award. It means a lot to me!

Check out the official TDIClub Chat Room!
Quote:
Originally Posted by BRUSSELS BELGIAN View Post
Maybe I should pay MYSELF to do bad work on my car!
compu_85 is offline   Reply With Quote
Old May 29th, 2009, 10:52   #3
mk3
Veteran Member
 
mk3's Avatar
 
Join Date: Sep 2005
Location: Wisconsin, USA
Fuel Economy: 46.4 lifetime
Default

G65 is the pressure sensor that puts out a duty cycle on the #2 pin. The general check to see that the system is charged is to make sure this give a proper value. I assumed the system had leaked because last year I had to recharge it.

I just noticed that Harbor freight has a manifold gauge set for about $40 so I'll pick one up on Saturday and set about learning how to use it.

I might also be able to troubleshoot using the G65 results but that would require making a wiring harness... and also the Fluke meter was borrowed so I do not always have access to that.
__________________
03 Jetta TDI 5-spd 320k mi PP520 Nozzles, IQ 5.8
13 Prius 135k mi
16 Civic 1.5L turbo (30k mi) ~ 37 mpg
mk3 is offline   Reply With Quote
Old May 29th, 2009, 11:26   #4
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

I appreciate the thanks, you are welcome.

You might look at the troubleshooting guide again. I just updated it an hour ago. It has a new section that covers general troubleshooting - or at least broaches the topic. It is not intended to be detailed.

The G65 is the high pressure transducer on his car.

It sends a duty cycle signal that is proportional to the discharge pressure on his AC compressor. 22% is about 80 psig or so, and is about right for the mid 70 ambient temperature range - with the compressor off.

Can you confirm that was the reading with the compressor OFF?

What is the reading with the compressor ON?

It sounds (on the surface) as if you are having either a compressor or an expansion valve problem. In order to tell for sure you will have to get a set of pressure gauges on the car.

Put on the pressure gauges and compare the high side pressure to the G65 reading. Determine what the low side pressure is. Prove you actually have a charge in your system, and prove the pressure transducer correct.

The next step (to be absolutely sure you are doing the right thing) would be to (have a shop) remove the charge and put in the right mass of refrigerant, then do the 3 tests in the repair manual to determine if the problem is the compressor or the expansion valve.

But what I would probably do would be to check the pressures, and if the discharge pressure really is that low with the compressor on, and the suction pressure was also high, (and it did not sound like shaking a steel can full of marbles), then I would try to replace the reed valve and compressor control valve, and see if that fixed it.

Replacing the reed valve and compressor control valve would involve removing the charge, then put in the new compressor parts, (put in a new refrigerant filter/drier), evacuating the system, then put the refrigerant charge back in.

jcrews, The Shootist, or joe tdi would be good folks to get a second opinion on this, I think.

But first you will need to know the pressure readings.
DanG144 is offline   Reply With Quote
Old May 29th, 2009, 11:49   #5
compu_85
Gadget Guy
 
compu_85's Avatar
 
Join Date: Sep 2003
Location: Springfield VA
Fuel Economy: 3.3 Mi/kWh
Default

I didn't realize the newer cars could read pressure through the engine computer. When did that come about? My 99.5 doesn't have this feature.

-Jason
__________________
Present:
2018 Tesla Model 3 DM. 50,000 miles.
2014 Cadillac ELR. 38,000 miles.
2013 Fiat 500e. 32,000 miles.
1991 Mercedes 350SDL 230,000 miles, 70,000 on engine. 18/27 MPG.
Past:
99.5 Jetta "GLX" TDI. 323,000 miles. Power Memory Seats, HIDs 11mm pump, BV39 Turbo, RCIII 36/47 MPG. Sold to JDSwann's Brother.
2012 Passat SE TDI DSG. 114,000 miles. LED tails, Memory Seat, HIDs. Bought back by VW.
2004 Touareg V10 TDI. 165,000 miles. Sold to Matt98AHU w/ flat camshafts.
1988 Audi 5000S Quattro, 1992 Jetta ECOdiesel, 1991 Jetta ECOdiesel.
Thank you for giving me the BUG*PWR award. It means a lot to me!

Check out the official TDIClub Chat Room!
Quote:
Originally Posted by BRUSSELS BELGIAN View Post
Maybe I should pay MYSELF to do bad work on my car!
compu_85 is offline   Reply With Quote
Old May 29th, 2009, 11:54   #6
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

While the transducer sends a signal to the Fan Control Module and Engine Control Module, I have not found a way to read it with VCDS. Darn it. You might be able to read it on the Climatronic or the new CAN bus cars with VCDS.

VW used this instead of a pressure switch, on A4 cars with Manual AC built after May 99.

I have to read it, just as he did, using a Fluke multimeter, or some other meter that lets you read % duty cycle.
DanG144 is offline   Reply With Quote
Old May 29th, 2009, 15:41   #7
mk3
Veteran Member
 
mk3's Avatar
 
Join Date: Sep 2005
Location: Wisconsin, USA
Fuel Economy: 46.4 lifetime
Default

Yes, I was reading pressure with the engine off.

At some point in the model years, the G65 is available through VAG-COM but not on my 03. As Dan said it goes to the fan control module.

I may try to read the analog voltage with my meter with the compressor on - it will roughly be proportional to the duty cycle I think.

I didn't know compressor parts could be purchased separately - where would I find those parts?

as I said, I will buy a gauge set tomorrow assuming they are in stock.
__________________
03 Jetta TDI 5-spd 320k mi PP520 Nozzles, IQ 5.8
13 Prius 135k mi
16 Civic 1.5L turbo (30k mi) ~ 37 mpg
mk3 is offline   Reply With Quote
Old May 29th, 2009, 18:04   #8
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

Yes, reading the duty cycle signal on DC voltage scales is roughly proportional to the duty cycle. I think it can be pretty rough.

Please post any pressure to duty cycle readings you get, and any pressure or duty cycle to DC readings.

In the latest troubleshooting paper (rev 6 dated today) it has a link (which I think works) to one source for parts; the part example used was the internal mechanical compressor control valve. I got the link from jcrews, if I recall correctly.
http://forums.tdiclub.com/showthread.php?t=242699 at the bottom of post #1.

I have no experience replacing compressor parts. That is why I referred to more experienced folks above.
DanG144 is offline   Reply With Quote
Old May 30th, 2009, 06:44   #9
d2305
Veteran Member
 
Join Date: Jun 2004
Location: Pensacola FL
Default

If the compressor is working and you have no cooling, the refrigerant isn't getting to the evaporation coil. Get a thermometer and measure the vent temperature.
d2305 is offline   Reply With Quote
Old May 30th, 2009, 10:29   #10
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

As luck would have it a 98 NB gasser AC that came in today is having similar symptoms.

Only get warm air.

Compressor clutch engages and runs, both fans work.

Both high and low pressures are right at 115#.

The compressor sounds smooth, no abnormal noises or vibrations.

The compressor is an SD7V16, so it is a candidate for a proportioning valve.
DanG144 is offline   Reply With Quote
Old May 30th, 2009, 15:29   #11
mk3
Veteran Member
 
mk3's Avatar
 
Join Date: Sep 2005
Location: Wisconsin, USA
Fuel Economy: 46.4 lifetime
Default

I just hooked up the new gauges. The car has not been run all day, but it has been sitting in the sun.

With the engine off: Both pressures are 75 psi if I am reading the gauges correctly.

This seems to correspond with the duty cycle from the G65 that I recorded last week.

Next, I started the engine and turned on the AC and checked again after a while

With the compressor on: LOW 30 psi, HIGH 80 psi.

What can I conclude from that?

------
I checked the vent temperatures yesterday and turning the AC on drops the vent temperature from 78F to 72F.. pathetic.

I checked my other car (01 Passat) at the same time and it was drastically different - the vent temps with AC on went into the range of the mid 50F.
__________________
03 Jetta TDI 5-spd 320k mi PP520 Nozzles, IQ 5.8
13 Prius 135k mi
16 Civic 1.5L turbo (30k mi) ~ 37 mpg

Last edited by mk3; May 30th, 2009 at 15:48.
mk3 is offline   Reply With Quote
Old May 30th, 2009, 15:39   #12
steelmb
Veteran Member
 
Join Date: Apr 2009
Location: MB
Default

What are the pressures with the compressor running?
steelmb is offline   Reply With Quote
Old May 30th, 2009, 16:07   #13
mk3
Veteran Member
 
mk3's Avatar
 
Join Date: Sep 2005
Location: Wisconsin, USA
Fuel Economy: 46.4 lifetime
Default

summary: 03 Jetta with Manual AC

With the engine off: Both pressures are 75 psi

With the compressor on: LOW 30 psi, HIGH 80 psi.

Fans run, vent door seems to work, compressor spins as commanded (clutch works),

cooling effect is very slight - about 6F reduction in vent temp -- 78F to 72F
__________________
03 Jetta TDI 5-spd 320k mi PP520 Nozzles, IQ 5.8
13 Prius 135k mi
16 Civic 1.5L turbo (30k mi) ~ 37 mpg
mk3 is offline   Reply With Quote
Old May 30th, 2009, 18:31   #14
steelmb
Veteran Member
 
Join Date: Apr 2009
Location: MB
Default

First let me say that I am far from an A/C expert. However I do feel that the high pressure should be much higher with the compressor running and therefore feel that you are somewhat low on freon. If it were my car I would try putting some in. However it is your car so you have to decide. Perhaps you could hook up the guages to the 01 Passat for comparison purposes.

Last edited by steelmb; May 30th, 2009 at 18:33.
steelmb is offline   Reply With Quote
Old May 30th, 2009, 18:37   #15
scurvy
Good Ol' Boy
 
scurvy's Avatar
 
Join Date: Feb 2006
Location: Chicago IL USA
TDI(s): 2006 Golf
Fuel Economy: ☠☭
Default

Oh yeah, that's way low. You should be more like 50psi on the low side and several hundred on the high side.
__________________
If you post a question, post your solution!
mk4 front wheel bearing | scurvy winter front | VCDS in Chicago, IL USA
You are entitled to your opinions but not your own facts.
scurvy 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 02:16.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2020, 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 - 2020, All Rights Reserved
Page generated in 0.19667 seconds with 10 queries
[Output: 128.84 Kb. compressed to 107.49 Kb. by saving 21.35 Kb. (16.57%)]