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No defrost on Climatronic

2035 Views 2 Replies 2 Participants Last post by  Shkelzenrr
Hello everyone.
I have a problem with my CLIMATRONIC unit and I think it has started since retrofitting MFSW but that shouldn't have anything to do with it (other than maybe I damaged wiring?).
Everything works, I can have cold air I can have heat, but no flow to the floor vents or defrost, just the dash vents have air flow. I entered into Basic Settings in Vag-Com and it readjusted the (flaps?) and then I had flow to my floor vents but still not in the defrost vents near the windshield.
I did the self test and the codes coming up are 4F8 and 25B both related to the flap positioning motor.
But when I do the self-test I hear the motors moving and during the test the defrost vents have air flow it is just that during normal operation I can't switch the AC to defrost. I click the defrost button on the unit and nothing, even the led in the climatronic display doesn't light up.
Checked the connections they are all secure. Checked the fuses on the left side of the dash they are all fine. Are there other fuses/relays I should check or should I start removing the dash and replace the damn motor...
Thanks in advance for your help.

'04 Euro Passat
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I'd suggest you reset the errors (hold ECON 2+ seconds after the error codes all display after a test cycle). That might work.

A little background:
The dampers are just a 12VDC motor and a potentiometer for position feedback (0-5 VDC). The wires all go to the head unit. Relays internal to the head unit apply 12VDC of the necessary polarity to position the damper where it's needed.

Since the dampers do move to defrost and floor during the self test, you know the damper motors work. The problem might be the damper position feedback potentiometer, or maybe the head unit is just confused. You can monitor the damper position, e.g. channel 35 for the footwell/defrost damper.

That said, the lack of any action when you press Defrost makes me wonder about the head unit... Sorry I can't be more definite.
So yeah I replaced the climatronic unit and the problem was solved.
Weird how the unit gave up, will have to check what broke on the unit because it made me curious :poke:
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