Okay so its all fitted, and it works! However, its not perfect.

 

The ECU side works correctly, it switches on stage 1, stage 2, and then both stages (assuming alternator load is satisfactory). It also switches off when the coolant is above 80. But, the postion of the heater control dial has no affect on heater. So this means that the heater is always on, even when the temperature is set to cold. And that results in the heater just sitting in still air and getting very hot. That's probably safe but I doubt is how it's meant to work, and also waste fuel as its basically just heating up the bottom of the HVAC unit.

From the SSP, it states that if the heater dial is above 80% it should engage the heater. If I go into VCDS and check the HVAC, there is a field for Z35 (PTC) acivation, and that does turn on and off based on the dial postion (although there is a large delay for it doing so).

If I go into the ECU, and check VCDS, measuing block 16 shows information for the heater. Even when the dial is cold, the ECU goes through and engages the relays. There is a also a field for "Shut off conditions". VCDS lists things such as voltage, coolant temperature etc. For the heater to engage, all bits in that field are meant to be 0. However, the first one, which VCDS list as "Outside temperature above 5 degrees) stays at 1 regardless of outside temperature, and the ECU still engages the heater.

 

To further confuse things, there is an error in the wiring diagrams. My car has air conditioning, so this connection to pin 15 on the ECU, from the "Heater setting above 80% switch (F268) shoudldn't exist. However, there is a wire going into pin 15, that is permanetnly grounded. I've not checked where the other end goes, need to have the dash off again to look. I've tried removing the pin from the ECU connector, so it floats to 5 volts, and the ECU still activates the heater.

So my conclusion is there is possibly some incompatiblity between the ECU in my car and the HVAC controller. My car has a different ECU thank from the factory as it is remapped, and there is a chance that, even though its been flashed with the original data, there is hardware difference that is causing some odd behvaiour. I'm going to swap back to the orignal ECU and see if that gets me anywhere. If that doesn't help, I'm going to try a newer revision HVAC controller. I'm also searching for the correct contact assignment for the Fabia HVAC controller. It is "semi-automatic" climatic, in VW land. So it controlls the temperature via a moror. Currently, I can only find diagrams for climatronic, and fully manual climatic which are slightly different. That might offer some clues as to what I'm missing.

51 minutes ago, BilTechnik said:

My car has air conditioning, so this connection to pin 15 on the ECU, from the "Heater setting above 80% switch (F268) shouldn't exist. However, there is a wire going into pin 15

My interpretation of that part of the wiring diagram is that the solid black part shown will be present regardless of A/C or no A/C, but the dotted section from the firewall connector (T11b/9) onward to the HVAC unit (T16c/3)* will not be fitted.

 

I was unaware that there was more than one variety of Climatic system, I've never seen a wiring diagram with more than one.

 

*False assumption about where F268 is. Apparently only present in 'heating only' variants of the system. 

Edited 26 September, 20223 yr by Breezy_Pete

Yeah I think you're right, but there is something connected to the other end of it to ground the wire, and that's not shown on diagram which is confusing.

 

Yeah it explains it here. https://polo.blue/2018/12/17/swap-manual-climatic-ac-to-climatronic-ac-part-1-comparison-theory/

So he doesn't show "semi-automatic" Climatic, but its the same as manual climatric, without a mechanical connection to the temperature control dial.

Ah, OK. Polo 6R is a generation newer than what I've ever looked at. 

 

Yeah I only came accross it because it's about all the information there is. From what I can tell, the 6R is basically using 6N climate controls.

Done some further testing, I suspect the wire being grounded could have been false and its actually floating, which would match the wiring diagram. If I ground the pin of the ECU, the PTC deactivates, and if i let the pin float the ECU pulls it up to 12 volts and the PTC activates. I know of @Finn vRS and @bigngroovy who have this from the factory (who I've messaged) but does anyone have it? Ideally with VCDS to check coding.

The other thing I'm thinking it could be is I have  6Y0 820 045 C climatic module, which if you search on eBay, there are loads of. However, this is also a 6Y0 820 045 D specified, which isn't very clear what its for, just a different date range I think. So I wonder if that is the D variant has something to do with car which have aircon and PTC, aka have different software to transmit the PTC data over CANBUS. Again, if someone with PTC could confirm what module they have that would be great!

I decided to look in the FR (not an expert but can get by) for some clues, below is the flow chart concering "user-shutdown" of the PTC. It's sort of implied coolant heater but it is PTC

 

So cowFUN_HZE is referred to in DAMOS as "Cooling water heater" and in the FR is reffered to as this

The other bits are referring to ECOMATIC (start-stop). We want bit 0. So if bit 0 is 0, then "Input is dimKLI", which we can confirm by the diagram. When bit 0 is 1 (Input is dimKWH or no driver requst over CAN). Basically, when the bit is set to 1, the car is provisioning for PTC heater.

 

If we go back to the diagram, you can see at the top, dimKWH going into an OR block. dimKWH is the physical ECU pin that connects to F268 on cars with no airconditioning. This isn't present on cars with aircon. However, the fact I am able to disable by PTC by shorting this pin to ground shows that the cowFUN_HZE.0 bit is set to 1, which is a good start. Looking at the other leg of the OR block, there is an AND block with two inputs. cowFUN_KLI is a byte in memory that is used to tell the car if it has no climatronic, climatronic without CAN or climatronic with CAN. Climatronic with CAN is specified when cowFUN_KLI = 2. When cowFUN_KLI = 2, decoding of the CLIMA1 CAN frames in enabled, this frame is transmitted by the HVAC controller. mrmCAN_KLI.1 is then the "Driver request of Auxillary Heating" transmitted over CAN from the HVAC controller.

There isn't really any easy way of checking what cowFUN_KLI is set to without the correct DAMOS. I have 1.9 TDI DAMOS and in those cars, it is set to 2 as expected, but it is possible they just set it to 1 or 0 in the 1.4 TDI cars. Also, this only enables the ECU side of it, if the frames aren't being transmitted by the HVAC controller, and passed by the gateway then this still won't work. Next step is to keep looking for a 1.4 TDI BNM DAMOS file, and sniff the CAN frames that are being sent from the HVAC controller. Hopefully, the HVAC controller will be sending the requried information and it will just be a byte that needs changing in the ECU flash to turn the decoder on. If the frames aren't being sent, then I'll have to look at getting a D revision HVAC controller.

 

For clarification, the cowFUN bytes are stored in ECU flash and need to be changed the same way you would remap the car, you can't edit them with VCDS for example.

100% working PTC heater installed in a Fabia 1.4 TDI, fitted and working as it would be from the factory!

 

Off camera I'm turning the temperature dial from maximum to Minimum, in VCDS you can see that when the Dial is at Maximum, only the one "1" is shown on the second row, and the heating elements start to come on (third row). When I turn the dial down to minimum, a second "1" appears. That is the inhibit signal from the HVAC controller, and the heating elements immediately switch off.

I'll complete the Guide section next week, but to summarise. I would rate this as Medium/Hard depending on how confident you are with wiring, and if you have any other reason to have the dash off. If you have all the parts the retrofit could be easily completed in a weekend. For most/all 1.9 TDI there is NO CODING required, just plug and play which is great. For 1.4 TDI it may work, or there may be a change that you need to make which I'll detail later, but you'll need an MPPS/Galleto or similar cable to do it, it can't be done via VCDS. I'll also upload some results measuring the temperature inside the cabin with/without the heater.

@BilTechnikany final update on this? I'm looking at doing this with my vrs.

I've just done this conversion to my fabia last week 😎. Seems to work really well 😁