Skoda Yeti Frontscheibenheizung nachrüsten | Posts 16+

Glad to hear that the FSH is now heating up!

Pumuckl wrote:

The device draws approximately 50A. It is also protected with a 50A fuse.

Naturally, the fuse gets quite hot.
It's normal and harmless for a fuse to get warm. However, the crimp connectors in which the fuse is inserted make a significant difference. Some connectors have large contact areas and high current capacity, while others have loose contacts that result in higher resistance. If you've used good crimp connectors and can rule out any excessive resistance, I wouldn't change anything.
2. Question: Did you use the factory-specified cable gauges and lengths? The cable resistances affect the power consumption.

Pumuckl wrote:

I can turn on the auxiliary heater using the remote control. However, the climate control unit doesn't seem to recognize it, and it doesn't turn on the fans. Is there a way to teach it to do that?

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

guste100 wrote:

I wouldn't even be sure of that. If the control panel doesn't support STH, then it might also not activate the fans and flaps when STH is (remotely) enabled.

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

The extent to which the fuse heats up during "normal operation" is a design decision and depends on the potential fault scenarios. I personally find a 50A fuse for a 50A circuit a bit tight at first glance, but of course, it may have been designed that way. Especially considering that only 2x2.5mm² cable goes to the heating element itself. That's also why I'm asking about experiences regarding the current draw of the heating element.

Regarding the voltage drop issue with fuses: I don't have much experience with these fiber fuses and I'm not familiar with the different types available. I did some quick research over the weekend and found the following:

Littelfuse 0299050, 73mV.
ESKA 343.437 89mV

...and then there are also Maxi fuses in a compact design, such as the Littelfuse 0899050, which only have a 50mV voltage drop. That's why I'm asking about the standard Maxi fuse size 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 make individual contacts, please reach out to Mr. Deyter from DeyTrade. He took the time to really understand our needs, 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.

I've been reading about what people do when they retrofit an auxiliary heater. It seems to be a fairly common modification. My understanding is that they need to run a separate wire to the climate control unit (which should already be present in my car) so that the system knows the auxiliary heater is on, and then everything else should work automatically. However, I've also read that a firmware update for the control panel is often required. Does anyone here have experience with that?

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.
For comparison: in the Golf 7, the wiring has a cross-sectional area of 4 mm², splits into 2 x 4 mm², and is protected by a 40 A fuse. The rear window is supplied with 2.5 mm² wiring and is protected by a 30 A fuse.
At 2.5 mm², I see the limit for continuous current load as 20 A.
What cable cross-sections and fuse ratings are specified in the official and definitive 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 2.5mm², a current rating of 25A is permitted in a multi-core cable with 2 current-carrying conductors, and 32A when laid freely. For 6mm² cables, these values are 40A and 54A, respectively. Therefore, while not ideal, it is technically feasible.

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

Best regards,
Christian.

Hi Christian,
"Our Golf 7 doesn't have a windshield heating system, so I only have the data. How do you determine the permissible current strengths? "Single-wire, free in air" doesn't quite match the application, but okay. How are the 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 to the air nor run inside a conduit, it must be something in between. To determine the exact situation, one would need to measure the temperature of the cables. The current is evenly distributed between the two cables, so it's not usually a problem during normal operation.

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

If one of the two lines becomes significantly warmer, its resistance increases, and more current flows through the other line.

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

When dealing with high currents, particular attention should be paid to the connections, including cable-connector and fuse interfaces.
If a fuse is already getting hot, that's not a good sign and can create a feeling of unease in the long run.

It's important to be clear that some original fuse boxes are actually quite bad, 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 Based on my experience, adequately sized wiring is not critical as long as it doesn't get warm or is damaged.

That's not what I'm concerned about. If a circuit protected by a 50A fuse is carrying 50A under normal operation, and the fuse gets warm, then it's either a design flaw or something is wrong. Furthermore, in a comparable case, the Golf 7 only requires a 40A fuse for protection. The windshields can't be that different. The windshield being discussed must be designed in such a way that it is not overloaded, i.e., draws less than 50A, under ideal conditions (maximum onboard voltage, no significant voltage drop at the connector, fuse, or cables).
I was interested in understanding the cause, especially in the context of potential 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:

The disc being discussed here must be designed in such a way that, under ideal conditions (...), it is not overloaded, i.e., it draws less than 50 A.

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

A 50A fuse can be used continuously at 50A.
"I'm not familiar with the characteristics of automotive fuses. With household circuit breakers, the typical specification is that they can be continuously loaded with 50A at 30°C when rated at 50A."
They can also be operated with approximately 1.2 times the rated current for at least one hour (i.e., 60A).

Here, we're talking about a Fluidized Solids Hydrothermal (FSH) reactor. These are typically operated at temperatures below 30°C. Additionally, the FSH reactor automatically shuts off after 4 minutes and doesn't run continuously. Consequently, the entire system only heats up for 4 minutes and is still in the "heating-up phase," or hasn't yet reached its equilibrium temperature.
Considering these factors, I don't foresee any serious problems with using a 50A circuit breaker and 2x2.5mm² 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?

Excellent, especially with truly professional-quality wiring.
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. ZIt's likely.

Herbert.

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