Where can I draw a constant 12v for the Tekonsha 119250 Trailer/Wiring Harness?

[vesder21]

How are you guys running your wiring harnesses for a trailer? I've read a few posts about using a basic flat 4 harness for LED trailer lights, but I sometimes rent old Uhaul trailers, which have the old school incandescent lights so need something powered.

Therefore I would like to install the recommended Tekonsha 119250 (no splice) harness on my 2013 P85, but not sure how to wire up. From what I can tell person with ICE cars route this to their 12v battery, but it's such a pain to run cable up there so wondering if there is an easier or better way? Will the license plate lights or power lift gate be enough to power this harness?

Also anyone install one of these and have the wiring diagram? Some previous posts pair up the L, R, lights and ground to a singe (L or R side) of the tail lights vs. another member said you have to run from BOTH L and R taillights to each of the harness wires?

Any thoughts or help with this wiring would be appreciated.

 

[mb300sd]

Look up the install video and instructions for the lighted rear applique - you need most of the same wires. I made up a molex connector so I can unplug the applique controller and connect the trailer instead.

Edit: https://cdn.shopify.com/s/files/1/0196/5170/files/LightedRearAppliquecopy2.pdf
Has the location and color codes for all the wires you need. Colors may vary over the years - I think a few of mine didn't match.

 

[gasisnasty]

mb300sd - you must have a lot of time on your hands to basically strip the car apart to install wires - for what? Some vanity lighted appliqués. IMHO what a waste of time.

 

[vesder21]

yup, the new generation of Tesla owners criticizing before they even know what is going on. it was nice years ago when you could ask a question on the forum for community members to help.

mb300sd - your suggestions was very helpful and I was able to install.

no fun is being had here with the "wiring harness for a trailer" ;o)

 

[gasisnasty]

Quote "your suggestions was very helpful and I was able to install."
Really ? Where exactly in the rear did you hook up to a constant 12v outlet?

 

[LaurS]

I had some issues with the charging port I while working in the trunk I also wired the left/right turn/tail to a 4 pin female connector (PC AMP from an old PC power supply.)

Today I installed the trailer connector. I order the parts late at night and I was not sure what end I need so I bought 72" wire with both connectors and cut the end I did not need after doing the research: https://www.amazon.com/gp/product/B001EP0H7Q
I wanted optical isolation so I bought: https://www.amazon.com/gp/product/B00LW2GM84
Total about $15, I already had all wires and wire connectors/clips

I did not like to have the parking light ON to get the trailer lights to work correctly. See the attached picture on how I wired the relay board. It seems to work fine, although I do not have trailer for real test. I just measured the voltages at the trailer connector. I power it from the cigarette lighter when needed, and when not needed the 4 pin connectors is hidden behind the charge port cover.

 

[LaurS]

Correction for the input side

See the attached picture on how I wired the relay board.

 

[Willy3988]

Would a cigarette lighter adapter work?

 

[LaurS]

It should. Like I said I do not have a trailer. But a good cigarette lighter adapter with a 10A fuse should work fine. The one I use was from a 150W inverter that died. Just check the tip of the adapter, you do not want one that it takes almost no pressure to push it in. The stronger the spring the more likely it is rated for higher current.

 

[FMinMI]

It should. Like I said I do not have a trailer. But a good cigarette lighter adapter with a 10A fuse should work fine. The one I use was from a 150W inverter that died. Just check the tip of the adapter, you do not want one that it takes almost no pressure to push it in. The stronger the spring the more likely it is rated for higher current.

What is the manufacture date of your MS?

 

[LaurS]

I just updated my signature. 2014 P85.

 

[CB198]

I ran a wire all the way to the 12V in the frunk. Just realized today that it was causing problems with the DC-DC converter. The car was seeing 13.8V but from the cigarette lighter I measures 12.3V. Is there a way to wire the trailer light adaptor so that I won’t run into this problem again?

 

[CB198]

I had some issues with the charging port I while working in the trunk I also wired the left/right turn/tail to a 4 pin female connector (PC AMP from an old PC power supply.)

Today I installed the trailer connector. I order the parts late at night and I was not sure what end I need so I bought 72" wire with both connectors and cut the end I did not need after doing the research: https://www.amazon.com/gp/product/B001EP0H7Q
I wanted optical isolation so I bought: Amazon.com
Total about $15, I already had all wires and wire connectors/clips

I did not like to have the parking light ON to get the trailer lights to work correctly. See the attached picture on how I wired the relay board. It seems to work fine, although I do not have trailer for real test. I just measured the voltages at the trailer connector. I power it from the cigarette lighter when needed, and when not needed the 4 pin connectors is hidden behind the charge port cover.

After disconnecting the 12V to the trailer light adaptor, I connected the charging cable and got rainbow flash. Did this happen to you?

 

[cleverscreenam]

I ran a wire all the way to the 12V in the frunk. Just realized today that it was causing problems with the DC-DC converter. The car was seeing 13.8V but from the cigarette lighter I measures 12.3V. Is there a way to wire the trailer light adaptor so that I won’t run into this problem again?

The 12v power outlet is controlled by the MCU. When rebooting the MCU, the outlet switches off until it boots back up. Perhaps MCU isolates the 12v outlet from the rest of the car?