Skoda Yeti Frontscheibenheizung nachrüsten | Posts 16+

Glad to hear that the FSH is now heating up!

Pumuckl wrote:

Die Scheibe zieht ziemlich genau 50A. Abgesichert ist sie auch mit 50A. Die Sicherung wird natürlich entsprechend heiß.

"It's normal and harmless for a fuse to get warm. However, what makes a significant difference are the crimp connectors in which the fuse is inserted. These have contacts with a large contact area and high current load, but also loose contacts that have a higher resistance. If you used good crimps and can rule out any increased resistance at the connection points, then I wouldn't change anything."Question: Did you use the factory-specified cable gauges and lengths? The cable resistances affect the power consumption.

Pumuckl wrote:

Ich kann die Standheizung aber mit der Fernbedienung einschalten. Allerdings ist das dem Klima Bedienteil egal und es schaltet die Lüfter nicht ein. Kann ich ihm das irgendwie beibringen?

Unfortunately, I don't think so. In fact, I had already expressed that very concern earlier.

guste100 wrote:

Nicht einmal da wäre ich mir sicher. Wenn das Bedienteil keine STH unterstützt, dann wird es bei (per Fernbedienung) aktivierter STH eventuell auch keine Lüfter und Klappen ansteuern.

What happened to the control panel from the Passat with both buttons? Did you ever try using it, and was it just not possible to reprogram it for use in a Yeti?

How much a fuse heats up under "normal" operating conditions is a design choice and depends on the potential failure scenarios. I personally find a 50A fuse for a 50A circuit to be somewhat tight at first glance, but of course, it may have been designed that way. Especially considering that only 2 x 2.5mm² cables run to the heating element itself. That's also why I asked about typical current draw values for the heater.
Regarding the voltage drop issue with fuses: I don't have much experience with these fiber fuses and I'm not familiar with all the different types available. I did some quick research over the weekend and found the following:

Littelfuse 0299050, 73mV.
ESKA 343.437 89 mV.

...and then there are also maxi fuses in a compact design, such as the Littelfuse 0899050, which only have a voltage drop of 50mV. That's why I'm asking about standard maxi fuse designs with a lower voltage drop.

Regarding the cables:
I managed to find almost all the original contacts, except for the two power contacts of the relay. For those, I used a pre-made repair cable with a cross-section of 6mm². Since one end connects directly to the fuse holder and the other splits into two 2.5mm² wires, I didn't need to install any additional connectors.

If you ever need to find specific contacts, please reach out to Mr. Deyter from DeyTrade. He took the time to really help us, and we were able to identify the right contacts based on a few pictures he provided.

Regarding the control panel:
Unfortunately, I haven't been able to find the Passat part yet. If anyone has one and would be willing to give it away or lend it, please let me know.

Ich hab nachgelesen was Leute machen die nachträglich eine Standheizung einbauen. Das kommt ja wesentlich öfter vor. Mein Stand ist dass die eine extra Leitung zur Climatronic ziehen müssen (die sollte bei mir schon vorhanden sein) damit die weiß dass die Standheizung ein ist, und dann sollte alles weitere von selbst passieren. Allerdings ist des Öfteren die Rede davon dass man ein Firmwareupdate für's Bedienteil braucht. KenDoes anyone here understand this?

Best regards,
Christian.

Hi there,
mich irritiert die 50 A Last auf einer 2,5 mm2 Leitung, und dann auch noch mit 50 A abgesichert. That doesn't fit. / That won't work. / That's not right.
For comparison: in the Golf 7, the wiring has a cross-sectional area of 4 mm², splits into two strands of 4 mm² each, and is protected by a 40A fuse. The rear window is supplied with 2.5 mm² wiring and is protected by a 30A fuse.
At 2.5 mm², I see the limit for continuous current load as 20 amps.
What cable cross-sections and fuse ratings are specified in the official original wiring diagram?

hg
Herbert.

Hi Herbert,

It was all built according to the original wiring diagram. The 6mm² wire from the relay splits into two 2.5mm² wires.

For standard PVC or rubber cables with a cross-sectional area of 2.5 mm², a current rating of 25A is permitted in a multi-core cable with 2 loaded conductors, and 32A when laid freely. For 6 mm² cables, the ratings are 40A and 54A respectively. Therefore, while not ideal, it is technically feasible.

Do you have any idea what the power consumption of the windshield in your Golf 7 is?

Best regards,
Christian.

Hi Christian,
"Our Golf 7 doesn't have a windshield defroster, that's why I only have the data. How do you determine the permissible current strengths? "Single-wire, free in air" isn't quite accurate for this application, but okay. How are those 50A distributed between the two halves (measured)? Is the windshield original?"

hg
Herbert.

Hi Herbert,

The disc is original.

You can find the current-carrying capacity information in the technical documentation of any reputable cable manufacturer. In my Meinhart catalog, you'll find them at the very back. I'm sure those tables are also available online.

Since the cables are laid in a way that neither allows them to be completely exposed nor run within a conduit, it must be something in between. To determine this precisely, one would need to measure the conductor temperature. Under normal operating conditions, the current is evenly distributed across both conductors, so it's not usually a problem.

Greetings,
Christian.

Quote:

...The current is evenly distributed across the two lines...

measured or assumed?
hg
Herbert.

Herbert wrote:

Quote: ...The current is evenly distributed across the two lines... measured or assumed? hg Herbert

.
Wenn eine der beiden Leitungen signifikant wärmer wird, steigt deren Widerstand und es fliesst mehr Strom durch die andere Leitung.

Based on my experience, adequately sized pipes are not a problem as long as they don't get hot or damaged.

When dealing with high currents, the focus should primarily be on the connections, including cable connectors and fuses.
If a fuse is already getting hot, that's not good and it creates a feeling of unease in the long run.

It's important to be clear that some original fuse boxes are actually quite bad quality, for example, the one located on the battery of the Audi A3 8L.

If it were my car, I would try to prevent a fuse from overheating. Because over time, the contact will only get worse.

Best regards, Rainer.

Quote:

If one of the two lines becomes significantly warmer, its resistance increases, and more current flows through the other line. icon_cool.gif Nach meinen Erfahrungen sind ausreichend dimensionierte Leitungen unkritisch, solange sie nicht warm werden oder beschädigt sind.

Darum geht es mir nicht. Wenn in einem mit 50 A abgesicherten Stromkreis in normalem Betrieb 50 A fließen, und die Sicherung warm wird, ist das entweder eine Designmacke, oder etwas stimmt nicht. Zudem im durchaus vergleichbaren Fall Golf 7 40 A zur Absicherung reichen. So unterschiedlich werden die Scheiben ja nicht sein. The disc being discussed must be designed in such a way that it does not become overloaded under ideal conditions (maximum voltage at the terminals, no significant voltage drop across connectors, fuses, or cables), meaning it draws less than 50 amps.
My concern was to understand the cause, especially in light of the potential for overheating due to modifications not approved by the manufacturer.
The linear temperature coefficient of copper is 0.0038 1/K, meaning that for every 10°C increase in temperature, the resistance increases by 4 percent, and the current decreases accordingly.
hg
Herbert.

Herbert wrote:

Die hier diskutierte Scheibe muß ja so ausgelegt sein, daß sie bei idealer Versorgung (...) nicht überlastet, d.h. weniger als 50 A zieht.

I completely agree with the first sentence.
Regarding the second half, I have a different opinion.

A 50A fuse can be used continuously at a current of 50A.
"I'm not familiar with the characteristics of automotive fuses. With household circuit breakers, it's common for them to be able to continuously handle a current of 50 amps at 30°C when their rated value is 50A."
They can also be operated with approximately 1.2 times the rated current for at least one hour (i.e., 60 amps).

Here, we're talking about a fluidized sand heater (FSH). These are typically operated at an ambient temperature below 30°C. Furthermore, the FSH automatically shuts off after 4 minutes and does not run continuously. Consequently, it only heats up for 4 minutes and is still in the "heating-up phase" or has not yet reached its equilibrium temperature.
Considering these factors, I don't foresee any serious problems with using a 50A circuit breaker and 2 x 2.5mm² wiring.

Pumukl: How does the FSH current behave over time? Does it draw the same current with a frozen substrate as it does with a warm substrate, or does the FSH current decrease over the 4 minutes?

[Translating...]

Fein bei wirklich profimäßig durchgeführter Verkabelung.
Und da drängt sich die Frage auf, ob selbige auch in dem Betrieb wie hier https://community.dieselschrauber.org/en/viewtopic.php?p=253383#253383 durchgeführt wurde. Zu vermuten ist´s.

Herbert

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