Cabin Heating Problem E-Golf (Challenge)

[crunch81]

Good day People,

I have a very challenging problem. It's driving me nuts.

Situation: No Cabin Heat from High Volt Electric Heater (no heat Pump)

Important info:
-I Replaced HVAC Control Panel (Buttons which control fan, heat and A/C)
-Disconnected HV Battery and 12V Battery and left car overnight and reconnected.
-When I set the car to heating in de Weconnect app on my phone, the HV Heater also does NOT work.

Now comes the challenging part:
When I use OBDEleven to control the High Volt Heater, It works.
After I use OBDEleven to control the HV heater, my button panel (HVAC Module)  works for a short while, so multiple times I thought the problem was solved.
But the problem comes back after a few hours. The only way to get the Cabin Heat working again is to control the HV Heater directly through OBDEleven.
Buttons work, cabin heat is present, after few hours same situation repeats.

I do have Elsawin and took a deep dive in the wiringcharts but it is to difficult for me to make a conclusion.

My logical thinking would be: HVAC buttons module replaced/HV Heater works straight when asked by OBDEleven: Problem must be a Relay or a control module in the car.
I could not find a relay for the HV Heater (Why is there no relay for it) Also could not find a fuse for the HV Heater. And could also not find which control module is responsible for controlling the HV Heater.

Hope that someone could help me.
Thanks in advance for you reply.

E-Golf
2014
53.000 KM
No Heat Pump

[dv52 (Australia)]

Ramon: Hi and thanks for the message. WoW a MY14 e-Golf with only 53,000 kms!!

I'm happy to have a look at the wiring diagram for you - but you will need to send me a copy of the relevant pages. Probably the best way to do this is to post the document on a third party hosting site (like dropbox - don't use Google please) and send me a link via a message.

The other piece of information that I need is a copy of the SCAN report for the car.

Don

[crunch81]

Hi Don,

Thanks for taking the time to look at this!! 

The link to the Dropbox Files is sent throug PM

If you need something more, just let me know....

Just FYI: 

I do not have:
-Thermal Management Control unit J1024

Maybe you already know or could see in a instance when you are scrolling through the wiring diagrams but I thought I would just give the extra info.
For me it took quite a long time to figure out that I did not had this control Unit.

Thanks!

Greetings Ramon

[dv52 (Australia)]

Ramon: I suggest that you read Self Study Program-880153 - a copy can be downloaded from HERE

Clearly the from the SCAN report, the car is happy with the new J255 module -but what doesn't appear on the SCAN  is the long-code string for the new module. 

Question: did you modify the J255 long-code string as part of the retro-fit? Or, asked another way- did you make any attempt to align the long-code strings on the old and new Air-Conditioning modules?

Don

PS: I assume the Component Protection errors are because this car has a hacked MIB unit ?

[crunch81]

Hi Don!

Aug 21, 2023 10:17:38 GMT dv52 (Australia) said:

PS: I assume the Component Protection errors are because this car has a hacked MIB unit ?

This is correct!

Ramon: I suggest that you read Self Study Program-880153 - a copy can be downloaded from HERE

Thanks very much for the link, but this doc only apply to E-Golf with Heat pump, I have a PTC Electric heater without the Thermal management module and no Coolant circulation pump

Question: did you modify the J255 long-code string as part of the retro-fit? Or, asked another way- did you make any attempt to align the long-code strings on the old and new Air-Conditioning modules?

Yes, I did when fitted the seat heaters.

Long coding HVAC Module:
Coding did on 12-09-2020

Old Value:  00022200200100000005000200111802
New Value  00022200200100010005000200101000
 

Greetings,
Ramon

[dv52 (Australia)]

Aug 21, 2023 14:29:11 GMT crunch81 said:

Thanks very much for the link, but this doc only apply to E-Golf with Heat pump, I have a PTC Electric heater without the Thermal management module and no Coolant circulation pump

Yes, I'm aware that your version of "heat Pump" is different! My purpose in referring to the SSP was to highlight the absence of "relays" in even the more sophisticated heat-pump system. You mentioned 

"Problem must be a Relay or a control module in the car. I could not find a relay for the HV Heater (Why is there no relay for it) Also could not find a fuse for the HV Heater."

The SSP suggests (to me at least) that if there are electro-mechanical devices for controlling high-current loads in the heat-pump system, they will be physically present in the remote devices. However, my hunch is that the heat-pump circuits use electronic style relays (i.e. power transistors, or FETs).

That said, my review of your wiring diagrams confirms that there is ONE relay in this system. To make matters very obvious, I have grossly simplified a section of the VW wiring diagram below - again,  this a a very, very, very simplified circuit that is applicable ONLY to demonstrate how your retrofit exercise changed the factory connections - from a power supply perspective:

So - my understanding from your words is that you removed EX21 and retrofitted J255. As shown, the relevant fuses for this retrofit are SB35 and SC7 - and the pertinent relay is the Air conditioning system relay, which the wiring diagram calls J32. This relay provides primary power to J848 (as well as other stuff) and it is called R8 on the fuse panel in the engine bay.

However, I very much doubt that this will be the cause of your problems because you say that the heat pump works on some occasions!

Don

PS: I don't have a heating_and_air_conditioning repair-manual for the E-Golf -  but The following extract is from the equivalent document from a Golf mk7 (which shares a similar MQB platform DNA):

• If new heater and air conditioning controls - EX21- with Climatronic control unit - J255- is installed, the basic setting and an adaptation (“Compressor first run”) must be carried out in the "Guided fault finding" or in the "Guided functions"

I note that your SCAN report doesn't show an error related to basic settings - nevertheless I include this information

[crunch81]

Hi Don!

Yes, I'm aware that your version of "heat Pump" is different! My purpose in referring to the SSP was to highlight the absence of "relays" in even the more sophisticated heat-pump system.

Ah now I understand, I have read the document now and to be honest, for me it a lot of chinese in terms of making conclusions.


Thanks for the wiring diagram! It very clear to understand now what is changed after the retrofit.

So - my understanding from your words is that you removed EX21 and retrofitted J255

That is correct!

If new heater and air conditioning controls - EX21- with Climatronic control unit - J255- is installed, the basic setting and an adaptation (“Compressor first run”) must be carried out in the "Guided fault finding" or in the "Guided functions"



I note that your SCAN report doesn't show an error related to basic settings - nevertheless I include this information

Double Checked it, it is performed on the date of the retrofit, please see screenshots:






To be sure I performed the Basic Run In test again...

This relay provides primary power to J848 (as well as other stuff) and it is called R8 on the fuse panel in the engine bay.

I exchanged Relay R8 with R5 (which are the same) Same situation....



Also checked the fuses, fuses are ok. I noticed SC7 fuse is also controlling rear window heater relay, which is working ok.

[Carmaffia]

Important info:
-I Replaced HVAC Control Panel (Buttons which control fan, heat and A/C)

Did you replace the control panel by a identical type. The control panel for a petrol/diesel engine is different and would give you this problem.