Two curious things about AAN wiring...

[S2central.net]

Actually there are lots of curious things but here are two noteworthy things I discovered while poring over factory AAN diagrams for a KV conversion.

1 - F76 'R' pin does not enter the ECU as per ABY and ADU... This is the alarm signal used to turn off active boost control if water temp is excessively high. On the AAN it is only used to inform the climate control system about such a problem. I think this one has been discussed before with general confusion about why AAN is different.

2 - TCP - turbocharger coolant pump (afterrun) - This is NOT integrated with the AAN ECU either... On the ABY & ADU we have this being tickled for a few seconds when the key is turned on - often mistaken by many newbs and some 'experts' to be the fuel pump being primed. I would need to stick my head under the hood next time I see an AAN to confirm this one. On the AAN the TCP is activated ONLY by the thermoswitch - it is locked out from operating when the engine is running by the fuel pump relay... Whereas on the ABY & ADU there is a handshake/control with the ECU that yields the extra handy function of testing the TCP before the engine is started.

The 2nd item should be easy enough to retrofit on the loom... but of course the ECU would need ABY or ADU software to activate the test routine. I also suspect that the ABY & ADU uses a different afterrun pump controller as an extra pin is used...

Then again - can some kind AAN owner unplug their '324' relay from one of the passenger side connector stations in/around the footwell and tell me if it has 5 or 6 pins ?

[gerardiro]

I have one spare 324 relay which is broken. let me find it and you've got it

[gerardiro]

there ar 5 pins on the relay.

[gerardiro]

[s2_wot]

Paul, on my S6 the pump switches on as it should via the relay and thermoswitch. But it does not run for a couple of seconds at startup. I changed everything in an attempt to have it prime at startup (relay, thermoswitch) and cleaned all the connectors and then wrote it off as a glitch somewhere.

Thanks for clarifying.

[S2central.net]

excellent pics - thanks so much - but I am seeing 6 pins there... can you see if one is labelled '87b' please ?

[S2central.net]

Just checked that AAN part number for the 324 relay and it is the same relay as found on ABY and ADU... so thats good !

[S2central.net]

Paul, on my S6 the pump switches on as it should via the relay and thermoswitch. But it does not run for a couple of seconds at startup. I changed everything in an attempt to have it prime at startup (relay, thermoswitch) and cleaned all the connectors and then wrote it off as a glitch somewhere.

Thanks for clarifying.

Isnt it great when the real world lines up with the theory - well some of the time at least !!!

[gerardiro]

my mistake! there are 6 pins for sure! this is aan relay on audi 100 s4 1993.
I found old pics, not the relay by itself. keep looking...

[S2central.net]

OK - no worries then - must have 87b as it is the same part as ABY/ADU. Thanks for replying with swift evidence here !

[S2central.net]

To link the ECU with TCP controller (324 relay) you need to add a wire from ECU#41 to the 87b terminal on the 324 relay... Must stress again - this will likely only work on AAN if it has been upgraded with ABY or ADU software. Someone like prj could probably unpick where the code difference is in the chips but its not exactly a big whoop feature.

For AAN owners... ECU pin#41 presents itself on 'T6g' pin 3 as a white wire. T6g is a blue 6-pin plug in connector station #2. Fill your boots

[S2central.net]

Another possibility is that it will just work on a regular AAN ecu without any s/w trickery because pin 41 is a general purpose handshake pin for aircon etc... If nobody beats me to it - I will check on a local AAN motor next time I see it.

[UrS4boy]

Two curious things about ABY and ADU wiring

I would say that since the AAN was developed before the ABY or ADU, that the curious differences with the AAN are really ABY/ADU differences.

I always thought that your (Paul's) suggestion that the after-run pump (and the fans) run on AAN start up was wrong but since it wasn't (and isn't) a big deal, I let it slide.

The AAN after-run pump is only triggered by the after-run switch. Then it stays on for 10 minutes (via the 324 relay) or until the temp drops down enough. There is no need for the pre-run operation.

http://forums.quattroworld.com/s4s6/msgs/21503.phtml

[s2_wot]

top right hand corner

[Thuppu]

So, is there any way to test the AAN after run cooling system that it works? I have a new pump and 105C switch, but I'm not sure if the system works at all, havn't heard the pump go on at any point.