Questions about air heaters (Z35) with PTC elements + control unit

Defective electric air heaters (which heat the incoming air in the climate control unit, not a separate heating device) with non-erasable errors have been discussed here before, see for example /viewtopic.php?t=26006 and especially /viewtopic.php?t=28328.

I mean the auxiliary heater (Z35) with a PTC element, see the error message below - not a dedicated auxiliary heater. I have the version with the control unit (J604), which was installed in the Passat 2006 B6 up to week 43 of 2006.

The usual solution is found here (from the second of the links mentioned above).

Quote:

Helping was re-soldering the 5 larger resistors on the circuit board; these likely had cold solder joints. The heating has been working again since then.

However, I have also read that the control unit is often defective.

What I find surprising about the solution described above is that the device heats up during the actuator diagnosis, but not otherwise (Is it not being activated?). That would actually suggest a problem with the control unit, especially in sub-zero temperatures.

Therefore, two questions, before I take this thing out (which is supposed to be quite fiddly):

- If the control unit responds, outputs values, and performs an actuator diagnosis (see the image below), it's hard to imagine that it itself is faulty, right?

- Why does the auxiliary heater activate during actuator diagnostics, but never at any other time? (Temperatures are below zero.) (And there is also an error message.)

It's more of a theoretical question, but I don't really understand how it's supposed to work through a diagnostic process, but not through normal operation.
(if this is the case, but if not, would it be a control unit problem rather than one of the resistors that need to be soldered?)

Are the values shown in the image actually realistic? (I had also read about higher performance and larger currents, but the actuator diagnosis only had one option with the result shown.)

Quote:

Address 7D: Auxiliary Heater Label file: DRV\1K0-963-235.lbl Part number SW: 1K0 963 235 E, Hardware number: 1K0 963 235 E. Part: PTC element 0404 Revision: 00800000 Serial number: Operating Number: WSC 00000 000 00000 VCID: 2D56C4E2B48F672E11-8078 Sure, here is the translation of the text from German to English: "1 error found:" 00361 - Heating element for auxiliary heater (Z35) 014 - defective

Quote:

Enhanced identification. Serial number: Identification: BEB-001 Revision: 00800000 Date: 06.06.06 Test item number: 2100. Manufacturer part number: 4072 Software: K0404 Miscellaneous: Hardware number: 1K0 963 235 E VCDS Info: VCID: 2D56C4E2B48F672E11-8078 Label file: DRV\1K0-963-235.LBL

Error messages (English) for Ross Tech error code 00361: http://wiki.ross-tech.com/wiki/index.php/00361

Speculation:
In actuator diagnostics, the transistor is simply switched on and off.
Under normal operation, for example, the voltage supply, power consumption, or parameter 42 are monitored. If only the latter component is defective, then the actuator diagnostics and normal operation will not function.

Comparable to cheap LED light bulbs (with insufficient power consumption) in a car: they light up for 3 seconds and then turn off, and are then registered as defective in the error memory. It works, but the parameters for normal operation are not correct.

Greetings.
Guste.

Quote:

Why does the auxiliary heater activate during actuator diagnostics, but never at any other time?

A theory I recently read (in an English forum) suggests that the total heating power is likely 1000 watts (with a current of 70 amps).

Quote:

A heating power of 600 watts indicates that only 2 (out of a total of three) heating elements are functioning. Probably, this is why the entire heating unit is identified as defective by the control unit and not used.

Maybe it's just a theory, but it sounds pretty convincing to me (as an answer to my original question).

And please answer my further question about whether the power shown in the actuator diagnosis image is likely correct (it's currently at 2/3 of the rated power).

So, it's probably the recommended approach to resolder those five resistors on the circuit board.

While I've done some soldering and crafting before, I haven't yet worked with SMD components (i.e., soldering components directly onto the circuit board from above). I'll need to do some research on that first...

And I'm not really looking forward to the expansion either.

Quote:

During normal operation, for example, the voltage supply, the power consumption, or parameter 42 are monitored. If only the latter is defective, then the actuator diagnosis and normal operation will not work.

Yes, something like that, that makes sense.

See my reply to myself from earlier, which overlapped with yours. Same thought.

Best regards!

I'm having the exact same problem.

- Heating element for auxiliary heater (Z35)
014 - defective
- Diagnostic interface for data bus (J533): not present or incorrect.
005 - Basic settings / Adaptation.


I bought a used "tested" item from a seller on eBay, and I installed it today, but it has the exact same problem.

After installation, I activated the auxiliary heater using the actuator diagnostics, and it only reached approximately 600 watts and then slowly decreased to around 300 watts.

Has anyone had any success with soldering or using an oven?

I don't have any practical experience working on that specific control unit yet. But generally:

Surface mount soldering isn't rocket science. A reasonably fine soldering tip with a moderately powerful soldering iron should be sufficient for the job. Here, it's even about power resistors, so the power rating is more important than the fine tip.

If you have a DSLR or another camera with a decent macro function, you should be able to see the cracked solder joints. If you upload the image here, we'd be happy to help. You should still have that old control unit lying around somewhere.

The air heater consists of three heating elements. Similar to the Golf 3 era, with its three glow plugs in the water circuit. Depending on the voltage and temperature, either the low setting (one heating element) or the high setting (two heating elements) is activated, or both settings (all three heating elements) can be used. Based on the problems I'm reading here, it seems like the issue always arises with the smaller setting (the individual heating element).

That explains why the control unit sets the error, but still gets warm during diagnosis (thanks to the large heat sink).

So, it just needs to solder that small component in place.

PS 2: In the Passat 3C, the PTC heater was only used in the first few model years (I believe 2006 and 2007). Afterwards, the three heating elements were directly controlled by external relays (I believe from 2008) onwards). It seems they realized that a power control unit was not necessary for a simple heating element. It was probably originally intended to be a fast-responding PWM controller, but it was never actually implemented that way.

Regards,
Guste.

Thank you, Guste, for the detailed explanation and assistance.
This weekend, I removed the auxiliary heater from my brother's car (he has the same model) and resoldered the five resistors.

Before the upgrade, it had a maximum output of 300 watts during the actuator diagnosis.
First, I put the circuit board in the oven at 180 degrees Celsius for about 10 minutes.
After the oven, it went up to a maximum of 700 watts, but it still displayed the same error message.
Subsequently, it was expanded again, and the five resistors were "resoldered" by keeping the soldering iron on the resistor for approximately 5-8 seconds, with the tip also touching the connection point. However, it still has errors and is only capable of up to 700 watts.

"How do I know which is the small step and which is the large step on the circuit board?"

abicim wrote:

First, I put the circuit board into the oven at 180 degrees for about 10 minutes.

Uh, that's quite a crude method. I'm not sure if that was a good thing.

Most electronic components are not designed to withstand this temperature. Typically, they are specified for use up to 125°C in the automotive industry. Of course, this temperature for soldering can be exceeded, but 10 minutes is significantly longer than the soldering profiles I am familiar with.
Furthermore, soldering is typically performed with a peak temperature of approximately 240°C. In short: The duration might have been too long for some components, and the temperature might have been too short for the solder.
In mass production, a proper soldering oven follows very specific soldering profiles. For example, the temperature is precisely controlled by a ramp that increases to nearly 200°C within 2-3 minutes, then rapidly increases to 240°C within less than 60 seconds, and then decreases again.

abicim wrote:

(..) However, it still has flaws and only works up to 700 watts. How do I know which one is the small step and which one is the large step on the circuit board?

To do this, you need to examine the layout of the conductive traces. Please post a high-resolution and clear photo, and then we'll have a chance to help.

As mentioned, it's possible that you may have already killed something in the oven.

Hi,

Quote:

Furthermore, soldering is typically performed with a peak temperature of approximately 240°C. In short: The time may have been too long for some components, and the temperature may have been too short for the solder.

Okay, here's the translation:

"That's correct. The thing with the oven probably caused more harm than good; electrolytic capacitors, in particular, don't like prolonged exposure to high temperatures." At 180°C, with typical lead-free soldering fluxes, very little bonding is likely to occur.

I recommend soldering the connections manually using a soldering iron.

Best regards, Rainer.

Hello everyone,

I'd like to provide a quick update. Since I didn't have the professional equipment needed to potentially solve the problem, and after many unsuccessful attempts, I sent the auxiliary heater to ecu.de for repair. They repaired the circuit board, tested it, and sent it back. The whole thing cost 145 euros, mostly due to the extra effort (resulting from the unsuccessful attempts).

After that, I installed the auxiliary heater today and first read the error memory, and lo and behold, there were no more error messages stored.
Then the engine was started, and the actuator diagnostics were run. As can be seen from the Screenshot, the 1,000 watts are almost reached. I immediately felt the warm air flowing out.

Thank you to everyone for your support.

Best regards, Orhan.

Thank you for the feedback!