Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Trailer lights wiring

This site may earn commission on affiliate links.
I'm trying to install trailer lights but this damn car is not playing friendly.

Everything works except the tail lights. If I hook it to the right side tail wire it turns on when the turn signal is on. And if I hook to the left side tail light wire I'd does the same but only when the left signal is on. If I don't connect it at all then I'll have no tail lights.

When the brakes are on both signals are on like they should be but so is the tail which is whatever, since during braking max light is a good thing.

How the hell do I get tail lights that don't flash when the turn signal is on? I know which wire is which because I have the wiring diagram for my month/year car off the Tesla service manual. I'm slpiced into the wires that go right into the light housing so I don't get what the prob is.
 

Attachments

  • PXL_20220721_014907911.jpg
    PXL_20220721_014907911.jpg
    390.7 KB · Views: 1,033
  • PXL_20220721_014924656.jpg
    PXL_20220721_014924656.jpg
    357.2 KB · Views: 465
  • Like
Reactions: 2022S-LR
There's three solutions to this, one is a bit harder than the others.

Hardest: Build a two-relay "AND gate" such that the left and right tail light wires each trigger one of the relays, with the main power connecting through the relays - only when BOTH are on, will the tail light signal wire be shown voltage. This will require wires from both tail lights to meet somewhere (the relays)

Second hardest: Route a new wire all the way up to the passenger side wire loom inside the roofline coming from the liftgate. You can apparently find the tail light wire there.

Easiest: Turn the marker lights on manually whenever you have a trailer connected. Connect the tail signal wire to either left or right tail light harness as you likely already have done. This is what I'm choosing until someday when I get very very bored and have a couple extra relays laying around. I don't expect that day to come anytime soon.
 
There's three solutions to this, one is a bit harder than the others.

Hardest: Build a two-relay "AND gate" such that the left and right tail light wires each trigger one of the relays, with the main power connecting through the relays - only when BOTH are on, will the tail light signal wire be shown voltage. This will require wires from both tail lights to meet somewhere (the relays)

Second hardest: Route a new wire all the way up to the passenger side wire loom inside the roofline coming from the liftgate. You can apparently find the tail light wire there.

Easiest: Turn the marker lights on manually whenever you have a trailer connected. Connect the tail signal wire to either left or right tail light harness as you likely already have done. This is what I'm choosing until someday when I get very very bored and have a couple extra relays laying around. I don't expect that day to come anytime soon.
The wire you describe that is up in the lift gate is the same wire that is down at the lower lamps. if you look a the attached wiring diagram they connect to each other at Z11 and Z12.
But because im a person thatll test out *sugar* before i dismiss it ill take a look and tap into the one up there just to verify it doesn't work.
So out of curiosity i pulled off the plug from the lower light and poked around with the multimeter and all 3 lights have 12v anytime one of them is activated so i'm not sure how it partly works right since they are all on but not all on at the same time.

Capture.JPG
 
  • Like
Reactions: 2022S-LR
There's three solutions to this, one is a bit harder than the others.

Easiest: snip
Found it, under the plastic cover on the passenger side there is a wire loom and there is a DB/PK wire. I tapped into that one and the tail lights work without effects on the other stuff and the turn/brake don't turn on the tail light.
Looking at the wiring diagram it's not logical for it to work which is why it was the perfect candidate to test lol.
PXL_20220722_035654811.jpg
 
Towing with a base model 60, the trailer was a 4x6 enclosed V nose that stands just about 6 feet high. The reason was almost entirely wind resistance b/c I have the heavy items (tools) from it on a tray on the back of the car now and I'm holding at about 380 wh/mi at 82mph today.

This is also on a car that HAS a Tesla-installed 90 kw battery pack (done under warranty), but the "helpful" folks at Tesla decided to "fix tesla's mistake" last week and stole 30% of my battery's range from me and locked it at 60. I had been driving around on that full range for months since I bought the car. So now I get to cart around a battery that is 50% heavier than the car originally had, yet only have access to the range that the car "originally" had. Oh, but they were only too happy to say that I could have that range back, if I only gave the company $4500 ransom for what they just stole from me. The "100%" charge is good for just 209 miles, but with that trailer.... 77 miles from 100% down to 5% and about 6 miles remaining. That's unacceptable for a road trip.

I'm also seeing evidence now of what I suspected might happen - the battery degradation is calculated, as I have only been charging it to 100% (since I know unequivocally that 100% is ACTUALLY only 60% charged).... But the Tessie app is now showing me a 3.5% loss in capacity. The superchargers SHOULD be able to maintain full rate right to that "100%" level since it is only 60% in reality.... BUT that has ALSO been drastically slowed down - Now the fastest I have seen is only 110kw, and once it crosses around the calculated 80%, it drops down to just 66kw speed. This is FURTHER theft - of my time - since the supercharger does NOT need to limit itself.

The thing is.... stealing the range from my car is a terrible decision on their part. In JUST the one week since they did this, I've already told more than 20 people in person about how the company treats their customers and steals features from the cars to hold for ransom. I wonder how many people I will have told before anyone from the company FINALLY responds to my attempts to contact them to fix this? I wonder how much lost business that will lead to?
 
Last edited:
  • Like
Reactions: RNHurt
airborne spoon, I'm looking for the wire you tapped for the tail lights and can't find it. I'm not sure where the bundle you've photographed is located in the car, or maybe my 2015 Model S doesn't use the same color code. I assumed it ran along the passenger side of the trunk. By the way, it works because it's the license plate light signal.
 
airborne spoon, I'm looking for the wire you tapped for the tail lights and can't find it. I'm not sure where the bundle you've photographed is located in the car, or maybe my 2015 Model S doesn't use the same color code. I assumed it ran along the passenger side of the trunk. By the way, it works because it's the license plate light signal.
It's possible but I don't think they'd change something like that from 14 to 15. You can look at the service manual and it shows the wiring diagram.
 
Thanks for getting back to me so quickly. I checked and found my car uses the exact same wiring diagram. But in your earlier post when you said "under the plastic cover on the passenger side", I don't get where it is exactly.
From the trunk, passenger side, take off the plastic piece on the top that holds the parcel shelf on and then you see another plastic piece you can pop off on the corner where the seat locks into place behind that is the witeing harness.
I'd take another pic but my car is getting a new paint job so I don't have access to it.
 
I'm trying to install trailer lights but this damn car is not playing friendly.

Everything works except the tail lights. If I hook it to the right side tail wire it turns on when the turn signal is on. And if I hook to the left side tail light wire I'd does the same but only when the left signal is on. If I don't connect it at all then I'll have no tail lights.

When the brakes are on both signals are on like they should be but so is the tail which is whatever, since during braking max light is a good thing.

How the hell do I get tail lights that don't flash when the turn signal is on? I know which wire is which because I have the wiring diagram for my month/year car off the Tesla service manual. I'm slpiced into the wires that go right into the light housing so I don't get what the prob is.
Trailer?!
 
You'll be the coolest guy in the campground! Do you map out the charging stations with pull thru?
Nope it only takes about 1.5 min to drop the trailer if I need to back into a spot.
If it's a large station and mostly unoccupied I'll park sideways and take up 3-4 spots and leave a large note on my dash with my phone number in case it suddenly becomes busy, but so far every time I've done that it was just as slow when I returned as when I pulled in.