Additional heater Z35 not connected

Hello,

When I was looking for my faulty climate control motors on the weekend, I noticed that a brown cable with a cable clamp was lying in the passenger footwell near the heater.
After some research, I've found out that this cable belongs to the auxiliary heating element Z35. According to the wiring diagram, it should be connected to the ground point (606) near the gear lever. However, I am wondering why this is not the case.
I found the "+" side of the element in the driver's footwell and discovered that the connector is attached there. The cables from there end in the relay holder at relays J359/J360. Where the red/grey cable leads to a red cable, and the two rt/ws cables only arrive as a single rt/ws cable.
What seems strange to me is that the fuses that are actually supposed to be there, S276/S277/S278, are not present on the relay module. The cables go directly to the relays. I couldn't find a fuse anywhere.
After I measured the open cable end against ground today, there was actually a board network voltage present there after about 10 seconds. The voltage remains present until the engine temperature in the instrument panel reaches 90°C. This corresponds to a distance of almost 30 km at these temperatures. The wiring seems to be, at least, approximately correct.

Since I definitely don't want to connect a 1000W heater to the ship's electrical system without proper safety measures, and I'm making the ground connection, the following questions arise:
Why wasn't the mass (from the factory) connected?
Why are the fuses (S276/S277/S278)) missing from their designated location?
Where could the fuses be, if any?

The car is a:
Seat Ibiza, Model BJ, Years 2001-2002
Motor Code ATD

PS: The PR code 7E6 for Electric Air Heater does not appear in the inspection sheet.

Greetings
Jens

Today, I found 2x 40A fuses outside the relay box. The cable colors seem to match the heater.
Where could the third one be? Is the safety still hidden?
In the electrical diagram, after the fuses, you will find the connection:
A152 - Connection -5- (87), in the control panel wiring string
where can I find this connection?

[Translating...]

Hallo!
3 Sicherungen würden mich wundern. Es handelt sich um ein 300W Heizelement und ein 600W Heizelement. Damit lassen sich die 3 Stufen, geschaltet durch 2 Relais realisieren.

Gruss
Brezelmann01

[Translating...]

Hallo,

Ich habe mich geirrt, es handelt sich bei der gefundenen Sicherung lediglich um eine. Das schwarze in der Mitte der Sicherung ist eine Rastnase. Nach dem Stromlaufplan ist dies die Sicherung S276. Das rt/ge Kabel geht hier auf ein rotes. Das ist die Sicherung für die erste Stufe. Die 2 anderen Stufen sind laut Plan getrennt abgesichert über S277/S278. Ich finde nur leider weder die zwei Sicherungen noch die Verbindung A152 hinter selbigen. Ich müsste das komplette Armaturenbrett ausbauen, um die Kabel offen zu legen. Ich werde einmal versuchen, ob ich etwas mehr erkennen kann, wenn ich Bordnetzsteuergerät, den Relaisträger und den Potentialverteiler ausbaue. Das sollte relativ fix erledigt sein.

Grüße
Jens

[Translating...]

Hallo!
3 Sicherungen würden mich wundern. Es handelt sich um ein 300W Heizelement und ein 600W Heizelement. Damit lassen sich die 3 Stufen, geschaltet durch 2 Relais realisieren.

Gruss
Brezelmann01

Hello,

I have now removed the control unit and the relay box and found the other two fuses behind them. Subsequently, I connected the power connection, and lo and behold, everything is working.
The initial questions remain. But at least, it will soon be warm in the car.

Hello, Jens.