No power to driver's side headlight from VC Front

[emptyspaces]

I've been having a couple weird issues- the hazard lights flash when I start driving away, for example- however the new thing tonight is that the driver's headlight is out, which is making the wipers erratic. Perfect.

I checked the plug at the headlight, the passenger side has 14.5v on the outside, 11v on the middle and a ground on the other side.
The driver's side plug has no voltage on the outside, 11v on the inside and ground on the inside.

Service manuals show the line voltage power coming from "Body Controller, Front" which I would think is VC Front.

Anyone have any experience replacing the VC Front module? Sounds like it needs to be programmed with Toolbox.. Any idea what it costs to take it to Tesla?

Thanks

 

[FatFalcon]

What year is your 3?

You're correct, body controller front and VC front are the same.

I have a friend who changed our a VC Front, IIRC you have to do a software reinstall, coolant pump ID routine and headlight calibration routine. All of these can be done from the screen in service mode. Don't need any special access.

However I wouldn't just go and replace the module without checking the wiring and headlight first. For most components I there is a short to ground, internal fault or anything that's drawing too much current the controller will stop supplying power (e-fuse), it does not mean the controller is bad.

 

[emptyspaces]

What year is your 3?

You're correct, body controller front and VC front are the same.

I have a friend who changed our a VC Front, IIRC you have to do a software reinstall, coolant pump ID routine and headlight calibration routine. All of these can be done from the screen in service mode. Don't need any special access.

However I wouldn't just go and replace the module without checking the wiring and headlight first. For most components I there is a short to ground, internal fault or anything that's drawing too much current the controller will stop supplying power (e-fuse), it does not mean the controller is bad.

2018 (late 2018 build LR AWD), I figured out that the Gen 3.1 is just the newer version, the EPC doesn’t distinguish between the old and new VC Front clearly, but what I have is the original style with the battery +/- cables right on lugs on the front of it. I’m going to pull it out so I can check the wiring to the headlight first, but I’m suspecting it’s the module itself. I’ve been having some other weird issues with the car, like hazard lights flashing right when you start to drive away..

 

[emptyspaces]

For anyone who finds this in the future: I removed the cover for the VC Front module, and tested the headlight wiring back to the multi-pin connector where it plugs into the module. The wiring was good. Then I determined that possibly there was an E-fuse in the module that was not resetting so I left the headlight unplugged and re-powered the car, when it woke up and I tested the connector near the headlight it did have 14.5v as expected. I then plugged it into the headlight and heard it faintly whining and then it stopped and had popped the e-fuse again.

So, if you're trying to determine what is wrong, unplug the headlight or component, do a full power down (removing the rear seat and disconnecting the 12v multi plug on the passenger side) wait a bit and re-boot everything and see if you now have power at the item.. if you do, it's actually the component and not the supplying module..

 

[FatFalcon]

Good deal! Do your hazards still go off whenever you drive off? That's a weird one.

 

[CyberShy]

Sounds like you have a shorted headlight or headlight module. If you can pull one of the wires from the headlight connector, it may be the DRL portion, which you can live without (don't need it at night).

 

[emptyspaces]

@FatFalcon yep, for the last 3 or 4 software updates it’s been that way, thought it was a bug. When you get in the car the lights don’t flash for unlock, but when you start driving away they do. I still have the car all apart in my garage I’m going to try to get a headlight tomorrow and then put it all back together and see if that was effecting the flashing.

@CyberShy That might be possible by taking the headlight apart, but the plug into the headlight housing is only 3 wires. Batt +, Batt -, and CAN/LIN signal. All of the things that happen in the headlight/DRL/turn signal/High beam, are communicated on the CAN/LIN wire.

 

[CyberShy]

Oh. Well, then you might want to try replacing the headlight first. My guess is it is not the fault of the VCfront module.

 

[emptyspaces]

Oh. Well, then you might want to try replacing the headlight first. My guess is it is not the fault of the VCfront module.

Correct, that's why I was saying that the module not supply 14v as expected is due to it being an open e-fuse, and you have to unplug the component and depower/repower the car to property diagnose. Two scroll wheel reboot isn't enough to reset the e-fuse, so it will look like the wiring or module is still faulty.