Troubleshooting manual air conditioning system, Volkswagen Lupo 3L (Solution)

Hello,

Unfortunately, the air conditioning system doesn't work on my new toy. As far as I can tell, it's not diagnosable. The following steps have been taken so far:

* Refilling (vacuum test performed; approximately half of the refrigerant was missing - I suspect the vehicle has never had its air conditioning system serviced).
* Visual inspection - magnetic coupling appears not to engage.
* Air conditioning fuse checked (was OK).
* G346 Temperature sensor for compressor shutdown checked (approximately 1.03 kOhms at 15°C, approximately 2.3 kOhms after a few minutes in the freezer, approximately 0.33 kOhms after a few minutes in the oven) - I don't have the characteristic curve, but it seems to be functioning generally.
Resistance measurement of the climate compressor's magnetic coil: approximately 4 ohms (likely the input/output?).
* Voltage measured at the disconnected connector of the magnetic coil - consistently around 9.2V, regardless of whether the air conditioning is on or off.
* Checked the cable to the fan control unit (which also connects to the magnetic coupling) - it's okay.
* Pressure sensor G65 was temporarily replaced with a used one – no change in the situation.

I'm starting to run out of ideas. What else can be done that would be meaningful?

Bye.
peace

Hi Pax,

If the connector is disconnected, you won't be able to measure voltage at the magnetic coupling because the control unit detects this and shuts it off.

Since you've already checked the fill level: Just to test it, have you tried applying 12V directly to the magnetic coupling?

It's not uncommon for the compressor to become blocked due to a lack of refrigerant, and after that, the rubber pads on the magnetic coupling are usually damaged. However, you can only determine this after performing a 12V test.

If the magnetic coupling functions correctly after the test, then only the fan control unit in the engine compartment on the driver's side and its input signals remain as potential causes.
A) You've already measured the temperature sensor. I can't comment on the values themselves, but they seem plausible. Does this value also appear between pin 14 and 54 of the fan control unit (to rule out a broken wire)?
B) Connects to pin 14/8 and receives +12V (turns on the interior fan).
C) What signal is received at pin 14/3 from the engine control unit (ECU)?
D) Is pin 14/9 the ignition positive terminal?
E) 14/10 = Connection to the magnetic coupling?
F) 14/6 = Is mass present?
G) 14/7 = Coolant thermostat switch.
H) Continuous power supply to circuits 4/1+3 and 14/3? (Fuse SA4, 7, and
I) What is the issue with pin 14/2 (signal from the high-pressure sensor)?

My personal order of tests:
1) 12V to magnetic coupling.
2) Point H, check the fuses.
3) Then the rest.

Greetings.
Sure.

Here is the translation of the text from German to English:

"Guste" means "gust" in English. It refers to a sudden and strong gust of wind.

Hello,

Please upload the vehicle's Autoscan data and check the A/C deactivation conditions within the measurement blocks. Is it a Climatronic system or a manual one?

Best regards, Rainer.

Hello,

Thank you for the suggestions. Unfortunately, I only have time to work on the car during weekends, and the upcoming weekend is already booked. Therefore, the flow of information might be a bit slow.

@guste100:
I didn't dare to apply an external current to the magnetic coupling because it would have required me to fiddle with the small connector that had only two wires – I wasn't comfortable doing that.
It's certainly an important point to only take measurements with the A/C compressor engaged. But how do you practically achieve that? All the connectors are sealed.
I would now try to obtain some connector housings and build an adapter. However, this only works with the connector for the magnetic coupling. You can't get anywhere with the control unit using this method, or is there a simpler way (I actually don't want to cut any wires)?

Regarding point H, I have completed the following: In addition to checking the circuit breakers in the main electrical panel (SB26), I have also inspected the fuses in the engine compartment (both blade fuses and strip fuses).

Point I: Is that the G65? As far as I know, it generates a PWM signal. I haven't measured anything yet (and I haven't even checked the cable with a multimeter), but I have at least replaced the sensor with another one (used).

@Rainer:
It is a manual air conditioning system (see subject).
Autoscanning (not from the weekend, but the error was already present).

Code:

Sonntag,01,April,2012,14:43:54:01334 VCDS Version: RKS 11.11.2 Datenstand: 20120130 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Fahrzeugtyp: 6X - VW Lupo Scan: 01 02 03 08 15 17 19 25 35 37 44 45 55 56 Fahrzeug-Ident.-Nr.: WVWZZZ6EZ3W000615   Kilometerstand: 256670km ------------------------------------------------------------------------------- Adresse 01: Motor        Labeldatei: RKS\045-906-019-ANY.clb    Teilenummer: 045 906 019 AE    Bauteil: 1,2l R3 EDC 0001DS  1537     Codierung: 00002    Betriebsnr.: WSC 01233     VCID: 58B5E540B8084A3    WVWZZZ6EZ3W000615     VWZ1Z0B2123738 Kein(e) Fehlercode(s) gefunden. Readiness: 0 0 X X X ------------------------------------------------------------------------------- Adresse 02: Getriebe        Labeldatei: RKS\6N0-927-735.lbl    Teilenummer: 6N0 927 735 H    Bauteil: DS085 Getriebe      1390     Codierung: 00000    Betriebsnr.: WSC 00000     VCID: 3D7B54D4376A8FB Kein(e) Fehlercode(s) gefunden. ------------------------------------------------------------------------------- Adresse 03: Bremsen        Labeldatei: 6E0-907-379.clb    Teilenummer: 6E0 907 379 A    Bauteil: ABS     30 IE CAN  V006     Codierung: 05623    Betriebsnr.: WSC 01233     VCID: 2F677E9CED066DB Kein(e) Fehlercode(s) gefunden. ------------------------------------------------------------------------------- Adresse 15: Airbag        Labeldatei: RKS\6Q0-909-605-VW5.lbl    Teilenummer: 1C0 909 605 A    Bauteil: 2T AIRBAG VW51      0004     Codierung: 12884    Betriebsnr.: WSC 01233     VCID: 224187A8AED4D03 Kein(e) Fehlercode(s) gefunden. ------------------------------------------------------------------------------- Adresse 17: Kombiinstrument        Labeldatei: RKS\6X0-920-xxx-17.lbl    Teilenummer: 6E0 920 800 J    Bauteil: KOMBIINSTRUMENT BOO V10     Codierung: 00134    Betriebsnr.: WSC 45241     VCID: 28559580C8E83A3 Kein(e) Fehlercode(s) gefunden. ------------------------------------------------------------------------------- Adresse 19: CAN-Gateway        Labeldatei: RKS\6N0-909-901-19.lbl    Teilenummer: 6N0 909 901    Bauteil: Gateway K<->CAN             Codierung: 00006    Betriebsnr.: WSC 01233     VCID: F0E53DE0B0B8B23 Kein(e) Fehlercode(s) gefunden. ------------------------------------------------------------------------------- Adresse 25: Wegfahrsperre        Labeldatei: RKS\6X0-953-257.lbl    Teilenummer: 6X0 953 257    Bauteil: IMMO                0008     Codierung: 00001    Betriebsnr.: WSC 00000     VCID: FDFB14D4F7EACFB    WVWZZZ6EZ3W000615     VWZ1Z0B2123738 Kein(e) Fehlercode(s) gefunden. Ende   --------------------------------------------------------------------

I think I may have found the deactivation conditions while searching before, but I didn't note them down. I seem to remember something like 144 (ignition on, climate control on, engine off) or 0 (engine running, climate control on). I thought that at least sensor G65 might be diagnosable. However, there was something about guided troubleshooting, and I always get stuck with VCDS because I don't know what to do in those cases.

Bye.
peace

Hello!

Does the 3L engine also have fuses for the radiator fan located in the engine compartment? If so, try removing them and checking for corrosion. This is a known issue with the 6N and 6X models.

Is the air conditioning fan running?

Best regards,

"@brezelmann01: Yes, I checked the fuse box in the engine compartment, including the fuses, and they are all fine, and there's no sign of corrosion. However, the fan is not turning on."

"I finally received the connectors and connector housings and have built the adapter, so I can now safely energize the magnetic coupling on the air conditioning compressor and also take measurements while it's connected. However, different types of connector housings were installed than what was specified in the documentation. I haven't actually started conducting the experiments yet."

Here's the question again for everyone: The homemade adapter for the magnetic coupling should work for now. I still need to figure out how to practically measure things, for example, at the control unit or the pressure sensor. Are there any measurement adapters available? Or do you have to notch the lines or remove the individual wire seals?

Bye.
peace

Hello!
If the air conditioning fan isn't starting, you shouldn't immediately try to directly power the compressor! This usually means that either the temperature sensor at the air intake is faulty, the fan control unit (which also controls the compressor and everything else) is malfunctioning, or there might still be a problem with the fuses (still my favorite possibility). Turn on the AC and measure the voltage drops across the fuses near the battery.
P.S.: Is the measurement block for climate control on/off in the engine control unit being monitored? I mean, is the switch on the control panel actually working?

@brezelmann01: Thank you for your input. I'm not sure if the fan starts automatically with the air conditioning when the Lupo 3L is turned on, because energy saving is a priority. It might only start at a certain coolant temperature - but that's just a guess.

The "frost sensor" is likely the G346 (temperature sensor for compressor shutdown) – I have at least already checked its functionality with a small series of measurements (see my first post, point four).

The fuses appear to be in good condition, both visually and electrically. I cannot detect any signs of scorching or corrosion that are sometimes present in this type of construction (see picture).

Let's see when I'll have time again to take measurements on the car. Then I'll try to address the remaining open issues.

Bye.
peace

Hello,

Thank you for the help; the problem is temporarily resolved. The checklist from guste100 contributed significantly to this solution.

A positive wire leading to the fan control unit was so heavily oxidized under the insulation that none of the strands were sufficiently conductive. After being bent a few times, the cable completely broke.

For now, I've soldered a piece of wire in between to make the connection, as there was just enough cable left on the connector. Unfortunately, I haven't been able to remove the contact from the connector housing using my available unlocking tools. I tried using the timer contact release tools, but they seem unsuitable. How can I get the contact out, and with what tool?

Bye.
peace

Okay - and thank you for the feedback .

"In the Lupo 3L, the radiator fan also starts immediately after turning on the air conditioning. In addition to the original problem mentioned in the thread, the first speed setting of the radiator fan was also defective in this vehicle."

Bye.
peace

Thanks for the additional feedback after all this time. It's great to continue sharing knowledge in the forum.