MK7 and VCDS (VAG-COM) thread

[dv52]

Does anybody know if it's possible to set the indicators as DRL? I loved that VCDS option on the MK5.

ASKendrew: I'll leave the discussion about the legality of the change to local folk, but there is a more fundamental reason why it wouldn't be wise to make the turn indicators perform as DRLs.

Don't get me wrong - technically the tweak is very simple to implement using Leuchte programming. But the real problem is the electrical rating of the lamp base that VW installs in the two front turn signal fittings.  These lamp bases are designed to tolerate a 50% duty cycle - meaning that normally  the turn signal lamp oscillates with a switch-on time equal to the switch-off time. The DRL function however has a 100% duty cycle because when it is switched-on, the lamp is illuminated constantly. The impact on the turn signal fitting  from a doubling of the duty cycle means that the lamp base must tolerate a four-fold increase in heat (theoretically, the nominal heat generated by the lamps is I^2R, so twice the "effective" electrical current means four times the heat- I think!).

As some have found to their cost when  the turn signal lamp is used as a DRL (I'm aware of a forum colleague on VWVortex who tried this tweak),  the lamp base overheats and the neighbouring plastic components start to deform. Eventually, the lamp base fails!

So - I wouldn't recommend this tweak!!

Don
 

[itavaltalainen]

Good point about heat production. VW uses PWM on most lights - they don't control current but voltage afaik. I.e. 100% duty cycle compared to 50% means just twice the power (and heat output) not quadruple.

Could you not reduce the duty cycle in the LeuchteXX configuration? 

I changed the dim values for my DRLs in there, you can also do it for the indicators and pretty much any other set of lights.
Technically doing the chance is very easy, you only need to add the desired functions (in the correct order or rather priority!).

Just posting the original values here as back up.... Leuchte 0 and 1 are the fronts, 18 and 19 at the back.

(1)-Leuchte 0 BLK VL B36-Lasttyp 0   12 - Blinkleuchten
(2)-Leuchte 0 BLK VL B36-Lampendefektbit Position 0   34
(3)-Leuchte 0 BLK VL B36-Fehlerort mittleres Byte DTC-DFCC 0   14
(4)-Leuchte 0 BLK VL B36-Lichtfunktion A 0   Blinken links Hellphase
(5)-Leuchte 0 BLK VL B36-Lichtfunktion B 0   not active
(6)-Leuchte 0 BLK VL B36-Dimmwert AB 0   100
(7)-Leuchte 0 BLK VL B36-Lichtansteuerung HD AB 0   Always
(-Leuchte 0 BLK VL B36-Lichtfunktion C 0   not active
(9)-Leuchte 0 BLK VL B36-Lichtfunktion D 0   not active
(10)-Leuchte 0 BLK VL B36-Dimmwert CD 0   0
(11)-Leuchte 0 BLK VL B36-Dimming Direction CD 0   maximize
(12)-Leuchte 0 BLK VL B36-Lichtfunktion E 0   not active
(13)-Leuchte 0 BLK VL B36-Lichtfunktion F 0   not active
(14)-Leuchte 0 BLK VL B36-Dimmwert EF 0   0
(15)-Leuchte 0 BLK VL B36-Dimming Direction EF 0   maximize
(16)-Leuchte 0 BLK VL B36-Lichtfunktion G 0   not active
(17)-Leuchte 0 BLK VL B36-Lichtfunktion H 0   not active
(18)-Leuchte 0 BLK VL B36-Dimmwert GH 0   0
(19)-Leuchte 0 BLK VL B36-Dimming Direction GH 0   maximize

(1)-Leuchte1BLK VRB20-Lasttyp 1   12 - Blinkleuchten
(2)-Leuchte1BLK VRB20-Lampendefektbitposition 1   3E 
(3)-Leuchte1BLK VRB20-Fehlerort mittleres Byte DTC-DFCC 1   15
(4)-Leuchte1BLK VRB20-Lichtfunktion A 1   Blinken rechts Hellphase
(5)-Leuchte1BLK VRB20-Lichtfunktion B 1   not active
(6)-Leuchte1BLK VRB20-Dimmwert AB 1   100
(7)-Leuchte1BLK VRB20-Lichtansteuerung HD AB 1   Always
(-Leuchte1BLK VRB20-Lichtfunktion C 1   not active
(9)-Leuchte1BLK VRB20-Lichtfunktion D 1   not active
(10)-Leuchte1BLK VRB20-Dimmwert CD 1   0
(11)-Leuchte1BLK VRB20-Dimming Direction CD 1   maximize
(12)-Leuchte1BLK VRB20-Lichtfunktion E 1   not active
(13)-Leuchte1BLK VRB20-Lichtfunktion F 1   not active
(14)-Leuchte1BLK VRB20-Dimmwert EF 1   0
(15)-Leuchte1BLK VRB20-Dimming Direction EF 1   maximize
(16)-Leuchte1BLK VRB20-Lichtfunktion G 1   not active
(17)-Leuchte1BLK VRB20-Lichtfunktion H 1   not active
(18)-Leuchte1BLK VRB20-Dimmwert GH 1   0
(19)-Leuchte1BLK VRB20-Dimming Direction GH 1   maximize


(1)-Leuchte18BLK HLA60-Lasttyp 18   12 - Blinkleuchten
(2)-Leuchte18BLK HLA60-Lampendefektbitposition 18   8
(3)-Leuchte18BLK HLA60-Fehlerort mittleres Byte DTC-DFCC 18   16
(4)-Leuchte18BLK HLA60-Lichtfunktion A 18   Blinken links Hellphase
(5)-Leuchte18BLK HLA60-Lichtfunktion B 18   not active
(6)-Leuchte18BLK HLA60-Dimmwert AB 18   100
(7)-Leuchte18BLK HLA60-Lichtansteuerung HD AB 18   Always
(-Leuchte18BLK HLA60-Lichtfunktion C 18   not active
(9)-Leuchte18BLK HLA60-Lichtfunktion D 18   not active
(10)-Leuchte18BLK HLA60-Dimmwert CD 18   0
(11)-Leuchte18BLK HLA60-Dimming Direction CD 18   maximize
(12)-Leuchte18BLK HLA60-Lichtfunktion E 18   not active
(13)-Leuchte18BLK HLA60-Lichtfunktion F 18   not active
(14)-Leuchte18BLK HLA60-Dimmwert EF 18   0
(15)-Leuchte18BLK HLA60-Dimming Direction EF 18   maximize
(16)-Leuchte18BLK HLA60-Lichtfunktion G 18   not active
(17)-Leuchte18BLK HLA60-Lichtfunktion H 18   not active
(18)-Leuchte18BLK HLA60-Dimmwert GH 18   0
(19)-Leuchte18BLK HLA60-Dimming Direction GH 18   maximize


(1)-Leuchte19BLK HRC31-Lasttyp 19   12 - Blinkleuchten
(2)-Leuchte19BLK HRC31-Lampendefektbitposition 19   18
(3)-Leuchte19BLK HRC31-Fehlerort mittleres Byte DTC-DFCC 19   18
(4)-Leuchte19BLK HRC31-Lichtfunktion A 19   Blinken rechts Hellphase
(5)-Leuchte19BLK HRC31-Lichtfunktion B 19   not active
(6)-Leuchte19BLK HRC31-Dimmwert AB 19   100
(7)-Leuchte19BLK HRC31-Lichtansteuerung HD AB 19   Always
(-Leuchte19BLK HRC31-Lichtfunktion C 19   not active
(9)-Leuchte19BLK HRC31-Lichtfunktion D 19   not active
(10)-Leuchte19BLK HRC31-Dimmwert CD 19   0
(11)-Leuchte19BLK HRC31-Dimming Direction CD 19   maximize
(12)-Leuchte19BLK HRC31-Lichtfunktion E 19   not active
(13)-Leuchte19BLK HRC31-Lichtfunktion F 19   not active
(14)-Leuchte19BLK HRC31-Dimmwert EF 19   0
(15)-Leuchte19BLK HRC31-Dimming Direction EF 19   maximize
(16)-Leuchte19BLK HRC31-Lichtfunktion G 19   not active
(17)-Leuchte19BLK HRC31-Lichtfunktion H 19   not active
(18)-Leuchte19BLK HRC31-Dimmwert GH 19   0
(19)-Leuchte19BLK HRC31-Dimming Direction GH 19   maximize

[dv52]

Good point about heat production. VW uses PWM on most lights - they don't control current but voltage afaik. I.e. 100% duty cycle compared to 50% means just twice the power (and heat output) not quadruple.

hm....... Yes, the diming characteristics of Leuchte programming are PWM. However, PWM doesn't alter the fundamental laws of physics, so I'm not sure that I agree with your premise regarding power dissipation!

Let me invite you to consider the following logic (in the hope that I can change your mind):

1.  I assume that by applying a 100% duty cycle voltage to the turn signals (instead of 50%), the "effective" voltage is doubled. This is not strictly correct as I will discuss in my next post, but it is a good working hypothesis as a first-order assumption (I hope that you agree).

2.  The relationship between current and voltage is well established and it is inviolate of PWM - Ohm's Law I=V/R, or V=I*R.

3. The formula for electrical power is, Watts= V*I, and again it is unchanged by PWM

4.  Substituting the V form of Ohm's law in the power formula gives, Watts = I^2*R   (which is the formula in my first  post)
5.  Substituting the I form of Ohm's law in the power formula gives Watts =V^2/R

6.Since the same turn signal lamp is used, R in the power formulae above is constant - so it can be ignored for comparison purposes between 100% and 50% duty cycle situations

7. Therefore regardless of whether you use the electrical current form of the power formula (as I did in my 1st post), or if you apply the voltage form of this equation, the result is the same.  That is - power dissipation in the turn signal lamp will be  quadrupled if the voltage is doubled

QED

Don

[dv52]

Could you not reduce the duty cycle in the LeuchteXX configuration? 

I changed the dim values for my DRLs in there, you can also do it for the indicators and pretty much any other set of lights.
Technically doing the chance is very easy, you only need to add the desired functions (in the correct order or rather priority!).

By saying "reduce the duty cycle in the LeuchteXX configuration", I assume that you are referring to altering the dimming level of the turn signal  lamp when it is used as a DRL (i.e. via the Dimmwert value for the "alpha-pair" in the appropriate "Leuchte sub-set").

Yes, this is an alternative way of recognising the limited electrical capacity of the turn signal fitting. But, in addition to dramatically reducing the illumination level of the turn-signal as a DRL in daylight when the greatest illumination is needed,  there are some additional complications that have to be considered - IMO.

As many here will be aware, Leutche programming accommodates two lamp types; incandescent and LED. Also, and again as many here will know, LEDs are current devices whereas incandescent lamps are voltage devices. 

The setting that is used to tell the BCM which type lamp is installed is the "Lasttyp" adaptation channel. Using either LED, or incandescent setting in this  adaptation channel fundamentally alters the form of PWM that is applied to the lamp. For example, here is the voltage trace  for a "Lasttyp" setting of LED and for a "Dimmwert" setting of 50% (I made this screen-shot some time ago, so I can't remember which particular Lasttyp value I used))



Notice that notwithstanding the dimming level of 50%, the duty cycle of the square wave is 60%. I've looked at the voltage traces for a number of Lasttype settings and it appears that there are a range of different characteristics that alter depending on the chosen option. One particular variation is the frequency of the square wave - for LED settings in general (but not all), the frequency is 200 Hz (5 msec), but for incandescent lamps, the frequency tends to be 100 Hz.

So, all this is a long way of me saying that in order to get the power rating correct when using the turn signals as DRL via your proposal, care needs to be taken in selecting the "Dimmwert"  and the "Lasttyp" setting.

With a CRO and a bit of experimentation, it is certainly possible. Please share your findings if you decide to investigate this option

Don

[scanesare]

Question regarding the E-VAQ diff: Do we know if it can be adjusted via VCDS? I have a feeling the only cars that have it set to its most aggressive locking level are the Clubsport S and the Cupra and would be interested to check if we had access to its locking setting.

There hasn't been any direct official statement to that but is a conclusion I've drawn by comparing several reviews including GTI PP, Leon Cupra, Clubsport, Clubsport S so might as well not be the case, still very interested to see whether there's any sort of accessing it. Obviously since it's electronically controlled there must be some way of selecting different intervention levels but the question is whether that can be done via VCDS or requires external software/hardware.

[itavaltalainen]

In a normal DC circuit with normal R I would agree - however the resistance of an incandescent bulb is anything but constant.
Measure the resistance of a cold 12V 5W bulb..... that is 1 or 2 Ohms. Whereas Ohms Law would tell you it's around 28 Ohms. Just saying.... My guess was that with PWM it probably works out as only around twice the power if you double the voltage from a moderate duty cycle (or dim value).

[dv52]

In a normal DC circuit with normal R I would agree - however the resistance of an incandescent bulb is anything but constant.
Measure the resistance of a cold 12V 5W bulb..... that is 1 or 2 Ohms. Whereas Ohms Law would tell you it's around 28 Ohms. Just saying.... My guess was that with PWM it probably works out as only around twice the power if you double the voltage from a moderate duty cycle (or dim value).

I don't mean to be argumentative, but alas -  again I must differ (my apology in advance)!

First, let's be clear - the resistance that's important for heating is the illumination resistance (which for a 5 Watt lamp is 28.8 Ohms at a nominal 12 Volts) I 'm not so sure that the change in resistance for incandescent lamps is substantial in 12 volt circuits, but let's assume that it is for the sake of my reply!

Think about how incandescent lamp operates in the blinker mode. These lamps are designed to  fully illuminate during the switch-on phase. It's obvious that this is what happens if you look at the lamps in operation (IMO)

They must operate this way because the thermal mass (and therefore the thermal time constant) of the filament in the lamp is very small compared to  the flash rate.

By design, at 50% duty cycle, the turn signal lamp is dissipating it's full rated power during the switch-on phase of the blinker cycle. It's just that the lamp is only switched-on for half the time which results in the lowered long-term heat-rating of the lamp base/turn signal fitting Clearly these items have a substantially larger thermal time constant than the lamp filament itself, but the thermal mass of lamp base/fitting is similar to the heat generated in the 50% duty cycle of the turn signal (hence it's limited heat rating)

So any change in resistance due to the filament heating (if this is indeed substantial) is largely the same in both 50% & 100% duty cycle scenarios.

But I sense that you are wedded to your belief that the power is doubled when voltage is doubled. So, let's just agree to differ
Don

PS: if you are measuring 1-2 ohms for a functioning 5 Watt lamp when cold, then I would respectfully suggest that  you switch the scale to a lower value, or you try using a high impedance meter!

[itavaltalainen]

No worries wasn't thinking you were particularly argumentative.
I agree with you that P goes up by a factor of four if voltage goes up a factor of 2. Think I have expressed it a little vaguely.

Afaik 100% on dim level is still PWM controlled and not equal to full 12V (or closer to 14V with engine on). Because it does not light up well when cold I think VW uses more than 50% duty cylcle for 50% dim value (think your oscilloscope showed 60% 'on' time?).
Hence my guess that power would only roughly double for 100% dim value (VW may see dim value as % of light output which is not entirely linear to input voltage). It might be a bit more than twice - was merely guessing. Using the word 'voltage' in context you highlighted was incorrect by me and dim level would have been much more accurate.

The 1-2 Ohms was from memory (but it was definitely a single digit value) - I could repeat my 'experiment' but it is significantly less than the 25-30ish ohms you have on a hot bulb. As for measurement setup.... high current rated wires used on a Fluke 189 multimeter, not a 9.99 B&Q special offer;)

[zoom_cool]

I have just try and apply the Auto HVAC 08 VCDS tweek to display temp on Sat Nav screen, however it has done nothing and doesn't display temp on screen when I adjust the temp via the control knobs. Has anybody else got this to work.

[p3asa]

Have you got a picture or link to what its meant to do?