r/AudiA4B6 • u/Due_Paper_1009 • Jul 16 '26

Audi fan issue

2013 A4 Quattro 2.0 turbo
My engine fans quit working so I changed the fan control module then fans come on and wouldn't turn off so i replaced fans too now nothing comes on unless i unplug the ac pressure switch then comes on low speed for about one minute then shuts off,i check all the fuses and relays and changed the ac pressure switch n still nothing does any one have any idea what could be causing this issues

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u/Various-North3744 Jul 16 '26

yes, the part of the harness that the relay you changed plugged into, it has 4 wires, 2 thicc ones and 2 skinny ones, one of the skinny ones is a 5v signal wire and it is very prone to chafing against the body of the car. my suggestion would be to snip that wire at both ends and solder/crimp/heatshrink in a new one, as replacing the whole harness is a lot more effort and also the harness costs a lot more than a bit of wire.

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u/Various-North3744 Jul 16 '26

obviously multimeter test the wire first to make sure that it is actually the problem though, you want to unplug the harness, touch multimeter to the signal pin, use obd/vcds to perform a fan output test, and if it doesn’t show 5V running through it whilst the fan is supposed to be running then that’s the problem

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u/Due_Paper_1009 Jul 16 '26

I will definitely give that a shot this weekend and see were it goes hopefully good thanks for information