New air con controller problems

Hi guys,

 

I may have bitten off more than I can chew with this project. 

 

I have a Mk1 Fabia Elegance 1.9TDI ('03 plate). Basically, I replaced the hvac control unit, and can't get it to work. Detail:...

 

The original problem was that it would randomly blow super hot air, and moving the dial, turning the air con on/off would revert it back to normal. Then it would randomly blow hot air, but wouldn't be changed back to normal. I'm aware this has been discussed elsewhere. Finally, it would only blow hot air, except on a rare few occasions. This is regardless of the position of the temperature dial.

 

So I stripped the dashboard off and took most of the hvac system apart as best I could without touching the heat exchanger and refrigerant system. All the temperature sensors, fresh/recirculated air motor, blower, temperature control motor, seemed to work fine. I drove the car a bit like that, there were no warning lights, it was mechanically sound.

 

I may have had a couple short circuits, with audible sparks, when the blower speed dial circuitry hit the rest of the A/C circuitboard  :peek: Yes, i did dissasemble the control unit which is specifically says somewhere not to disassemble  :peek:.

 

I bought a new control unit, tested, working, from a breaker, not fancying Skoda's quote, and fitted it. 

 

Apparently it needs to be coded to the car - basic settings to get the min/max values of the flap motors. Thing is, it won't let me do this on VCDS, I can see fault codes, and erase them, and read measured value blocks, but not output tests, adaptations or basic settings. From memory I think it says "Error: Function/Group*** not available" respectively. 

 

Pulling the error codes, the fresh/recirculated error now seems to be throwing an error, which is odd because, just before replacing the old unit's circuitboard with the new unit, even though the fresh/recirc button didn't work, you could hear the motor working when reverse gear was engaged. But that doesn't happen now. Have I blown it with short circuits? or does it just need a basic settings? The temperature motor isn't throwing an error code, and that's the one I originally thought was the problem, getting stuck and giving me dodgy heat. It may still be the problem...but no DTC?

 

I cleared all DTCs for the whole vehicle, my local techie warning me that VCDS, or any control module, wouldn't perform a basic settings while there were error codes flagged. I then drove the car and took a fresh list. The DTCs from before wiping are shown in list "A" below, and from after wiping then driving are shown in list "B" below.

 

Needless to say, Basic settings still wouldn't work, else I wouldn't be here. Three codes from the HVAC cleared, but came back after driving, one code from the engine is new, I haven't seen it before.

 

I'm currently investigating the High Pressure Sender G65 as I do not know what it is, and hoping beyond hope there's a simple wiring fault fro the alternator load signal and the HPS that I can fix easily which will clear all faults. I cannot fathom the control unit (j238?) not working as I just bought it! Similarly, with the fresh flap motor V154, as I know it worked before replacing the unit, as above. 

 

My plan, failing the location of a simple wiring fault, is to replace g65, v154 and j238  :'-( , starting with whichever's cheapest. The alternator terminal, I don't know, I'll have to take a peek under the bonnet, but it sounds like that's a fairly common wiring problem, and easy to fix. Failing this, I think I'll have to take it to a dealer and sell my soul to satan to afford it. or scrap it and get a new one. In other words, I'm running out of ideas.

 

Thanks for any help in advance,

 

VCDS reports below.

 

Cheers,

 

J

 

 

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LIST A

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 For HVAC ONLY before installing new unit

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LIST B

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Whole car scan after installing new hvac control unit, clearing codes, and driving 10 miles, leaving car for the day, driving 10 miles back.

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