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Discussion Starter · #361 ·
Splicing on the wiring harness is almost done. I decided to invest in a ratcheting open barrel crimper and have been pleased with it so far.

I have a manual HVAC swap question for to folks.

There's a wire from the 7A MFTS to the climate control head that tells the system it's okay to run the compressor. It prevents the AC compressor from coming on in an overheat scenario. Does anyone know where that wire goes for the manual HVAC?

This signal also goes to the 3B ECU, pin 36. I'm thinking it needs to go to the AC clutch relay, but not sure which terminal. If anyone has a wiring diagram for a B4 cabriolet manual HVAC, I should be able to figure it out.

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Discussion Starter · #362 ·
Worked on the battery relocation today. Just mocking it up in the engine bay because I will need to do some painting. I plan on running an Odyssey PC925 with the following:

  • Negative 2/0 to gas tank bolt
    [/*]
  • Negative 2/0 from passenger front frame rail (procon-10 bolt location) to transmission
    [/*]
  • Positive 2/0 from battery to 200 amp breaker
    [/*]
  • Positive 2/0 from breaker to battery terminal at firewall
    * Positive stock cable from firewall terminal to starter
    * Positive stock cable (from 7A harness) from firewall terminal to fuse panel
    * Positive from firewall terminal to headlight relays
    * Positive from firewall terminal to 70 amp high speed fan relay[/*]













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Discussion Starter · #365 ·
jbrentd said:
Splicing on the wiring harness is almost done. I decided to invest in a ratcheting open barrel crimper and have been pleased with it so far.

I have a manual HVAC swap question for to folks.

There's a wire from the 7A MFTS to the climate control head that tells the system it's okay to run the compressor. It prevents the AC compressor from coming on in an overheat scenario. Does anyone know where that wire goes for the manual HVAC?

This signal also goes to the 3B ECU, pin 36. I'm thinking it needs to go to the AC clutch relay, but not sure which terminal. If anyone has a wiring diagram for a B4 cabriolet manual HVAC, I should be able to figure it out.

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To follow up on this...

I did some testing on the MFTS and the 2/R terminal (the one that goes to the AC clutch relay) is a normally open circuit. In other words, it doesn't send the signal until the temp is high. Although not ideal, I'll probably roll without that signal. That'll mean my AC won't shutoff automatically in an overheat scenario.

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Discussion Starter · #367 ·
jonas-k said:
Looks like that signal goes to terminal 13 of the AC Clutch control module.

https://12v.org/urs/1996_Audi_Cabriolet_System_Wiring_Diagrams.pdf
Thank you! So, if I'm not mistaken, the B4 cabriolet's AC clutch control module/relay (aux panel positions 3 & 4) is different from the B3 AC relay (aux panel position 4).

This shows what you confirmed...that the MFTS 2/R wire goes to terminal 13 on the AC clutch control module.



And for the B3, the MFTS 2/R wire goes to the AC control head. From here, I assume it goes to the AC programmer and then to the AC clutch control relay (terminal 5/T).



 

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jbrentd said:
Thank you! So, if I'm not mistaken, the B4 cabriolet's AC clutch control module/relay (aux panel positions 3 & 4) is different from the B3 AC relay (aux panel position 4).
That's how I'm reading it, but I'm no expert.

jbrentd said:
And for the B3, the MFTS 2/R wire goes to the AC control head. From here, I assume it goes to the AC programmer and then to the AC clutch control relay (terminal 5/T).
Makes sense. What's missing from much of the Bentley is an explanation for how it all works together. But I guess from a repair perspective that isn't really needed.

Also, I really enjoy following your build. Very useful for when I did my own 20vt CQ swap this past June. And it keeps giving me reminders for all the things I need to do when next I have the engine out, etc.
 

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Discussion Starter · #369 ·
Battery now lives in the trunk. Not sure why, but the idea of relocating the battery used to stress me out. I would over think cable size, relay location, etc.





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For the radiator fan wiring you might want to have a peek at this thread with refrence to how I wired mine, Depending on the quality of your fan, The cheaper ones don't do well with the sudden start of a relay switching on.
https://www.motorgeek.com/viewtopic.php?f=5&t=215329
HTH
 

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Discussion Starter · #373 ·
rally3 said:
For the radiator fan wiring you might want to have a peek at this thread with refrence to how I wired mine, Depending on the quality of your fan, The cheaper ones don't do well with the sudden start of a relay switching on.
https://www.motorgeek.com/viewtopic.php?f=5&t=215329" onclick="window.open(this.href);return false;
HTH
Thanks for that. I do remember seeing that thread.

I plan on driving the 200's 500w fan via an OEM resistor pack for speeds 1 & 2 and a 70 amp relay, using the original wiring.

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Discussion Starter · #375 ·
Just to clarify, I'm using the original wiring as a trigger for the 70amp relay. Using new, heavier gauge wiring for the high speed between the battery/fuse/relay/fan.

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jbrentd said:
Just to clarify, I'm using the original wiring as a trigger for the 70amp relay. Using new, heavier gauge wiring for the high speed between the battery/fuse/relay/fan.

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that will do it.
 

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Discussion Starter · #377 ·
Dealing with more BS not related to the swap...rust on the door sills this time. I forgot to take pics before I started. The before pictures are from 2014, so it had gotten worse since then.





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Discussion Starter · #378 ·
There used to be a guy on the S2Forum who made carbon fiber door sills. Does anyone know if those are still an option?

Spent some time today to continue cleaning the engine bay. Gonna hit it with a fresh coat of pearl before the 3B goes in.







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jbrentd said:
There used to be a guy on the S2Forum who made carbon fiber door sills. Does anyone know if those are still an option?

Spent some time today to continue cleaning the engine bay. Gonna hit it with a fresh coat of pearl before the 3B goes in.







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Looks great.

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