Ah. Not good.
Dodgy Demister
- Thread starter andys
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- heated rear window
Not sure they would even do mine under warranty, in the first month of ownership I added an extra wire into the bcm to add a door locking switch to the driver's door which it didn't come with.
Yes, when the heater element is disconnected - there is a kind of 5.7 V on the left connector. Actually it seems to be a pulsed signal at 200 Hz - need to have closer look into using a scope. Anyway, the important part is that a regular multimeter shows 5.7 V. I think this suggests that the +feed wiring is connected all the way up to the BCM.
Based on a quick try the tests work as advertised.
Button light test activates the light but not the heater (no relay click).
Heater test clicks the relay. VCDS throws up on the display presumably alternator current (was 52A) which seems to be about right when heater is on. The button light does not illuminate.
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heres my output tests, (Base battery load was 10A"drive current"(that would be coolant pump, DRL`s, BCM ignition etc etc)
HRS Z1 - which i dont have (no relay click heard and no additional battery load)
152747:
Heated front screen Z2 - (no relay click heard and 38A additional load on battery)
152810:
Heated external mirrors Z4 & Z5 (relay click heard at the BCM location, additional 6A battery load)
153033:
.....................
so no obvious relay action on the front screen.
HRS Z1 - which i dont have (no relay click heard and no additional battery load)
152747:
Heated front screen Z2 - (no relay click heard and 38A additional load on battery)
152810:
Heated external mirrors Z4 & Z5 (relay click heard at the BCM location, additional 6A battery load)
153033:
.....................
so no obvious relay action on the front screen.
The engine was not running?
@andys any chance of a picture of your current BCM byte15 settings?
While @andys was out compared codings of 08:HVAC and 09:Centr.elec with mine. A difference was "the connection" with mirror heaters and rear heater. But that shouldn't be an issue...
Confusing part is the mysterious, steady 5.7 Volts. If that voltage would really exist across heating element that would mean 10 Amp draw... trying to think how loose/broken cable on either on +feed or ground side would cause that... because it looks like the van tries to fire up heating but detects something... not enough current draw?
- Have you measured resistance from ground to right connector (or silvery strip in the element next to) - should be less than 0.1 ohm.
- From ground to left connector (or silvery strip in the element next to) - should be about 0.5 ohm.
- From right to left connector (heating element) should be the same about 0.5 ohms.
The above would just verify that the heating element is ok. And basically grounding...but...
Bypassing factory ground wire in the loom could be done by a separate parallel wire from right connector to proper ground... to see if it works then...
And tailgate closed - I'm not sure if that would make any difference...
Interesting, don't know - never looked into tests in this area - yet
Okay, the first thing I tried was changing the coding to the same as @mmi, 0xF4, this didn't change anything. It turned out I had selected the push-to-talk option in Byte 15 Bit 0 as I thought earlier. Removing this made no difference but it means my coding in Byte15 is now 0xD4.
So on to the above
1) resistance is 0.07 ohms - in line with expectations
2) resistance 0.8 ohms - slightly higher
3) resistance 0.4 ohms - in line with expectations
Then connected the right connector to a chassis ground - made no difference.
So does it look like it is the BCM? This is what I was really hoping it wouldn't be
So even though you have no HRS the BCM was still happy to run the output test whereas on mine it came up with "Inactive"!
why is the "heated front screen" not ticked? have you not got one?
have you tried ticking it anyway? - possible shared source from the BCM.?
this is my readout.
have you tried ticking it anyway? - possible shared source from the BCM.?
this is my readout.
I don't have one. Yes I have tried ticking and unticking all of the options in this byte but nothing made any differencewhy is the "heated front screen" not ticked?
this is my readout.
why is the "heated front screen" not ticked? have you not got one?
have you tried ticking it anyway? - possible shared source from the BCM.?
have you tried ticking it anyway? - possible shared source from the BCM.?
I think we're time travelling due to editing
My answer is in the post before you ask it
another difference i noticed was mine have C and yours had B (7E0 937 090 B/C)
LOL - - - - -I think we're time travelling due to editing
have you tried ticking it anyway? and retest the switched output functions?
- possible shared source from the BCM.?
I haven't tried the output test with it ticked, but it didn't make any difference to the HRS when I tried it.
im thinking:
try adding bit-5 and restest the output tests,
then
try removing bit-2 and restest the output tests,
(i dont see what the CAN has to to do with HRS as the switch and element are both connected to the BCM, unless its looking for other inputs or data from the CAN Bus....... but saying that mine shows the VIA CAN enabled also)
i had a similar issue when i added HID lights with auto leveling on a T5.1 - i messed up the coding, its was via the LIN Bus not via CAN. seperate issue but demonstrated how flipping just ONE BIT can mess up the settings.
try adding bit-5 and restest the output tests,
then
try removing bit-2 and restest the output tests,
(i dont see what the CAN has to to do with HRS as the switch and element are both connected to the BCM, unless its looking for other inputs or data from the CAN Bus....... but saying that mine shows the VIA CAN enabled also)
i had a similar issue when i added HID lights with auto leveling on a T5.1 - i messed up the coding, its was via the LIN Bus not via CAN. seperate issue but demonstrated how flipping just ONE BIT can mess up the settings.
