Re: Heating | Posts 32+

Moin Moin,zu deinem Thema erst mal folgendes die Sache mit dem Kühlerreinigungszusatz lass es lieber falls es nicht unbedingt nötig ist.Die Sache hatt nämlich einen ganz grossen Haken,die Wasserpumpe wird von dem Zeug stark in mitleidenschaft gezogen.Ausserdem hast du geschrieben du hast die Wapu erneuert,es gibt soweit ich Informiert bin eine geänderte Wapu für den C4 mit dem 5 Zylinder TDI Motor .Die Wasserumwälzung wird dadurch stark erhöht.

That's an interesting point about the modified VAPU; however, I no longer remember which one I have installed.

Anyway, I completely drained all the coolant and flushed the system (heat exchanger, radiator, engine separately) thoroughly with a garden hose in both directions, then added new coolant, and now it's heating up like new. The coolant is still perfectly clear.
I left the electric pump installed; it's permanently powered on via terminal 15. Additionally, I disconnected and plugged the vacuum hose from the heating valve to ensure that the heat exchanger is flushed even in summer. Hopefully, this will prevent it from clogging up so quickly again.

By the way, I found a repair manual for the 'Heating, Air Conditioning for Audi 100 1991 ->' on www.erwin.de, and it stated that there is an electric auxiliary heater located behind the heat exchanger, which activates below 5°C. So, there are no glow plugs in the coolant.

In this context, I had previously obtained the repair manual "Heating, Air Conditioning for Audi 100 1991 ->" from www.erwin.de and found that there is an electric auxiliary heater located behind the heat exchanger, which switches on below 5°C. So, no glow plugs in the coolant.[/quote]
While it's the latest technology and is being advertised as a new feature for the current A6, I don't really care. How exactly does it work according to the documentation? Specifically, how is it controlled and powered (e.g., fuse, wire colors)?

Wie wird das denn laut Erwin (siehe Fehlerdatenbank) gesteuert und versorgt (Sicherung, Kabelfarbe...) ?

Auxiliary heating element for vehicles with TDI engines from 06/94 onwards, for intermittent use. The TDI control unit only activates it under the following conditions (among others):
Coolant temperature < 70°C.
- Outside temperature at engine start < 5°C.
The heating element consists of 3 PTC heaters, each with a maximum current draw of 22 A, totaling 66 A. The connector for this is located behind the glove box (remove the foot vent). Wiring: 3 x 0.25 mm², red/black, red/white/blue, red/green.
Fuse S51 is located in the electronics box in the passenger footwell, behind the carpet (may require cutting).
The control unit is located on relay socket 6 of the auxiliary relay carrier III. The relay for high heating power is located in position 1 (Z. III) and is switched by pin 11 of the TDI control unit (2 out of 3 PTCs), while the relay for low heating power is located in position 2 (Z. III) and is switched by pin 9 of the TDI control unit (1 out of 3 PTCs).

Perhaps you can achieve even better heating performance in the winter by keeping the relay on setting 1 even when using a 'low heating output,' but for now, it seems more like summer.

Thank you.

The point where the air mass enters the interior also has something to do with the heating process. Since I replaced the pollen filter (about 15 euros), both the heating and cooling have been working much faster. By the way, the old pollen filter looked really disgusting, brrrrrrr. It had been in use for about 3 years or approximately 1250 operating hours. I will replace the pollen filter more frequently in the future.