Can’t find Brake Light Switch

oilbrnr

Member
Joined
Dec 18, 2001
Location
Connecticut
TDI
'12 Passat TDI SEL, '10 Dodge 2500 Cummins
I’m installing a sophisticated brake controller on my ‘12 Passat TDI SEL (Redarc Tow Pro Elite) which requires a trigger signal for brakes. Some are telling me that the signal from CHMSL is powered by PWM system ....this would not be acceptable. Additionally the circuit needs to accept nominal voltage in override mode to display brake lights when application is made from controller ( ....and just imagine the havoc this could create with the VW electronics diagnostics!). I spent considerable time under the dash looking at the brake pedal and hoping to find a simple micro switch. I could find nothing. Is it possible the electronic switch for lights is a hydro activated unit on the engine side of the firewall?
 

Jetta_Pilot

Top Post Dawg
Joined
Apr 14, 2005
Location
West Hill, Ont.
TDI
2015 Passat Highline TDI Candy White (SEL Premium) long gone 2002 Jetta TDI
Maybe a dumb question. Can you not just use the power supplied to the brake light bulbs? It sounds as if in addition you still have to feed a live 12 volt to this setup for controller use only.
 

Jedadiah

Veteran Member
Joined
Sep 17, 2010
Location
Central Kentucky
TDI
Former: '15 Passat TDI SE 6M, '15 Golf S 6M and '10 JSW
On my MK7 Golf the brake controller did weird stuff when connected to the brake signal wire. (It would be on at wired times, and activate if I touched the brake pedal when the ignition was off and the display would go to 5.4 and stay there until I let off the pedal) I opted to use the the third brake light output from the bcm instead and it worked much better. I’m not sure what number output that is on a nms though. Someone with Erwin access should be able to help you.

I think the nms uses a 3 plug bcm, but have never checked. My Passat has the same bcm part number as my JSW,which had a 3 plug bcm, did though. For the three plug bcm the brake signal wire should be Pin 17 in plug c according to the Westfalia universal trailer wiring instructions. It’s a a black and red wire.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
The newer cars use a Hall sender on the bottom side of the master cylinder, there is no "switch" in the traditonal sense. Which is why the OEM brake/trailer interface modules tap into the car's factory wiring via a plug that is already there and use the data that is available on the CAN bus. However since the NMS Passat is not a "real" Volkswagen, I doubt it has anything like that. But if anyone would know, compu_85 would.
 
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