Every Tesla uses a 12V battery to run the accessory systems and the contactor that connects the main pack to the motor. When the 12V is too low, the car appears completely dead. A 12V jump wakes the contactor and the car drives normally.
Why the 12V dies in the Puget Sound
Tesla owners in the metro hit dead 12V calls every winter. Cold wet mornings and long Sea-Tac airport sits are the most common patterns. The car sits for a week in the dark SEA garage and the 12V drains below the threshold needed to close the contactor.
The Model S and Model X use a traditional AGM 12V under the hood. The Model 3 and Model Y use a smaller lithium 12V also under the front trunk or under the hood depending on the year. Both wake the same way: jump the under-hood points, wait for the dashboard to light up, then start normally.
In the Puget Sound, the 35 to 45F band is the local pattern. Cold-soak slows the chemical reactions in the 12V and reduces its effective capacity. A Tesla that would start fine after a week parked in a mild garage will not start after a week in a 35F unheated garage.
What you need
A portable jump pack designed for EVs. The pack should have lithium-ion cells, reverse-polarity protection, and at least 1000 peak amps. Tesla’s own mobile connector can serve as a low-amperage wake, but a real jump pack is faster.
A pair of jumper cables and a donor 12V source also works. A second EV with a healthy 12V can serve as the donor. The donor’s traction pack is irrelevant. Only the 12V matters.
What to do step by step
- Open the front trunk or hood. The Tesla’s 12V jump points are under a red cover in the front trunk area on most models.
- Pull the red cover off the positive jump point.
- Connect the positive clamp from the jump pack to the positive jump point.
- Connect the negative clamp to the ground point on the body, not the negative terminal.
- Turn on the jump pack. The dashboard should power up within a few seconds.
- If the dashboard does not power up, the 12V is severely discharged. Leave the jump pack connected for 5 to 10 minutes.
- Once the dashboard lights up, disconnect in reverse order: negative first, then positive.
- Get in the car and start normally. The main pack should connect.
- Drive for at least 30 minutes to let the DC-DC converter recharge the 12V.
What not to do
Do not touch the orange high-voltage cables. The main pack is dangerous even when the car is off.
Do not try to jump the main pack directly. There is no safe way to do this from outside the car.
Do not use a gasoline car’s 12V as a donor if the cables are too short to reach the Tesla’s jump points without crossing the high-voltage cables.
Do not connect the jump pack to the 12V terminals directly. Tesla’s under-hood jump points are the right place.
When to call for help
A Tesla owner who is not comfortable with the procedure should call a mobile operator. Operators in the metro carry Tesla-specific 12V jump packs and the experience to wake a dead 12V without damaging the car. The call usually takes 10 to 20 minutes on site.
Mobile EV charging covers both 12V jumps and out-of-charge stops. The operator quotes before starting and bills the driver directly. Charge Pro SEA connects you with a local operator who knows the metro.
When to call
Call (206) 202-7018 when your Tesla will not start in the Puget Sound region. Charge Pro SEA connects you with a local operator who quotes before starting and bills you directly.