Installing Tekonsha electric brake controller
05-01-2019, 09:23 PM
#51
Junior Member
Tested with the trailer fully connected & the same issue is still present, the Brake circuit still gives 3.9v and the controller still assumes the brakes are being pressed, so rulled out that possibility!!
05-01-2019, 10:46 PM
#52
Junior Member
There is 2wire green connector at the back that I believe is the black/red & yellow/red wire connected to the controller, the black/red runs into the wiring harness that exits the vehicle for the 7 pin trailer plug. there is no black/red on the back of the 7pin, so it must be connected to the brake light somewhere inside the harness, it also reads 3.9v. Also tested all the outlets on the 7 pin, both the brake light & parking light pins read 3.9v without the trailer connected.
05-02-2019, 06:53 PM
#53
Junior Member
So the dealer spent the day changing the SAM & Testing Different Things free of charge & is Confident that the vehicle has no issues. So that leaves a potential issue with the controller I Guess, or trying a different brand! My search for a controller that wasn't under dash mounted may be squashed! Curt is sending me a replacement that I can test,
As I trouble shoot this, I was thinking that maybe there is an issue with the vehicle not recognizing thedigital controller due to a lower power draw (Similar to the issue with replacing incandescent with LED s)...maybe grasping at straw's.. but i guess its possible!!
As I trouble shoot this, I was thinking that maybe there is an issue with the vehicle not recognizing thedigital controller due to a lower power draw (Similar to the issue with replacing incandescent with LED s)...maybe grasping at straw's.. but i guess its possible!!
05-02-2019, 09:31 PM
#54
Junior Member
Installed a replacement Controller from Curt, Same issue...On another note, I connected a test light from the brake circuit to ground, when its connected, everything works perfect, line drops to 0v.....remove the test light, back to not working! So either the Vehicle see's there's a controller attached when I connect the test light, but not when just the controller alone is connected....I guess my next step is to try a different controller and see what happens
Last edited by clowrym; 05-03-2019 at 12:25 AM.
05-02-2019, 11:47 PM
#55
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'21 AMG53 wDPP & ARC, 19 GLC300 - Former- 10&14 ML BlueTecs, 20 GLE450 E-ABC, 15 Cayenne D, 17 Macan
The entire car is connected via CANBus - an electronic superhighway that allows all the components and computers talk to each other. It was introduced by Bosch in the US in the early 90s. It's digital so it doesn't require a separate wire for each function. So more things can talk (airbags, radio, wipers, seat, transmission and all OBD2 stuff.
As I understand it, the control unit (rear SAM in our case) in a CANBus sends frequent periodic signals out to check for modules that want to talk to it. When the signal (millivolts I think) gets a response, it takes action - in this case, sending current somewhere. The receiving module needs to decode the test signal and respond digitally.
What I think we may be seeing at 3.9v is that millivolt signal, which doesn't do anything without the appropriate (and communicative) receiver. Once the SAM makes a handshake, it knows you are trailering and all the trailering features kick in - tranny, blind spot, anti sway, trailer light out, etc.
It MAY have nothing to do with the brake control signals - maybe somebody else here knows what specific signal the SAM is looking for.
Anyway, I suspect that all our worries are not applicable.
I sure don't understand the Curt red light - green light system. Maybe its Can-Phobic, but that wouldn't make sense because CANBus is on all vehicles today because of the OBD2 (I think). The Curt may not even see a millivolt signal, or care about it if it does. (Conjecture)
What we use is a Tekonsha RF. We used a P3 at first but I didn't like the controller placement. So I just ignored all the Green Plug work I had done and installed the RF unit. It required drilling on the trailer A frame, but the in-cab controller only plugs into a 12V source (cig lighter) and has a coiled cord to the head unit. It doesn't have any accelerometers in it - they are in the unit that we mounted to the trailer.
The biggest advantage of the RF, for me, was that I strap it to the center console grab handle, right at hand. It requires no interior holes. And I know that it works with both our former W164 and current W166. Both with factory hitch, and required no intervention from the Service Department. (Unfortunately the W166 did away with the grab handles, so it's not as handy as your W164. I may just use velcro to mount it and deal with the glue later.)
By the way, both our W164 and W166 had/have LED taillights, and our trailer has incandescent.
Also, BTW, I liked the W164 better for various reasons. What surprised me is that, even with the much higher HP & torque ratings, the W166 isn't as strong. Towing, from a light (more turbo lag), or high speed passing. Lower mpg, too. But the DEF tank isn't under the spare, and we actually have a spare!
As I understand it, the control unit (rear SAM in our case) in a CANBus sends frequent periodic signals out to check for modules that want to talk to it. When the signal (millivolts I think) gets a response, it takes action - in this case, sending current somewhere. The receiving module needs to decode the test signal and respond digitally.
What I think we may be seeing at 3.9v is that millivolt signal, which doesn't do anything without the appropriate (and communicative) receiver. Once the SAM makes a handshake, it knows you are trailering and all the trailering features kick in - tranny, blind spot, anti sway, trailer light out, etc.
It MAY have nothing to do with the brake control signals - maybe somebody else here knows what specific signal the SAM is looking for.
Anyway, I suspect that all our worries are not applicable.
I sure don't understand the Curt red light - green light system. Maybe its Can-Phobic, but that wouldn't make sense because CANBus is on all vehicles today because of the OBD2 (I think). The Curt may not even see a millivolt signal, or care about it if it does. (Conjecture)
What we use is a Tekonsha RF. We used a P3 at first but I didn't like the controller placement. So I just ignored all the Green Plug work I had done and installed the RF unit. It required drilling on the trailer A frame, but the in-cab controller only plugs into a 12V source (cig lighter) and has a coiled cord to the head unit. It doesn't have any accelerometers in it - they are in the unit that we mounted to the trailer.
The biggest advantage of the RF, for me, was that I strap it to the center console grab handle, right at hand. It requires no interior holes. And I know that it works with both our former W164 and current W166. Both with factory hitch, and required no intervention from the Service Department. (Unfortunately the W166 did away with the grab handles, so it's not as handy as your W164. I may just use velcro to mount it and deal with the glue later.)
By the way, both our W164 and W166 had/have LED taillights, and our trailer has incandescent.
Also, BTW, I liked the W164 better for various reasons. What surprised me is that, even with the much higher HP & torque ratings, the W166 isn't as strong. Towing, from a light (more turbo lag), or high speed passing. Lower mpg, too. But the DEF tank isn't under the spare, and we actually have a spare!
Last edited by mikapen; 05-02-2019 at 11:54 PM.
05-04-2019, 04:00 PM
#56
Junior Member
I did have a look at that one, I ended up getting a relay from mercedes that I wired inline, It has a resister across the ground/power that allows the vehicle to recognize the controller and all is working good now!!
