2018 Tesla Model 3 Engine Problems

High voltage fast charge contactors experienced partial weld failure (BMS_a167_SW_FC_Partial_Weld) during routine Supercharging, causing complete HV system shutdown (hvState = HV_DOWN). Vehicle also threw BMS_a085/a086 Pack and Fast Charge Contactor Mismatch codes. Tesla service is refusing to cover repair under the 8-Year HV Battery Warranty, claiming fast charge contactors are not a warranted component despite being integrated into the HV battery assembly. Vehicle has been at Duluth, GA Tesla Service Center since approximately June 8, 2025.

NHTSA ID

11743421

Incident

Jun 7, 2026

Tesla failed to properly diagnose a high-voltage battery isolation fault in my 2018 Model 3. Despite safety-critical BMS_a027 and BMS_a142 faults indicating multiple isolation failures, they skipped required insulation resistance testing, falsely blamed sand in a connector, and charged me $174.95. After the issue returned, they reversed course, replaced an internal battery contactor, and reduced the $1,173 estimate to $356—admitting fault without owning it. Days later, a diagnostic showed dangerously low isolation resistance (380kΩ, far below Tesla's 1,000kΩ safety threshold), yet they took no further action. On July 12, the car again went into limp mode. Tesla’s repeated failure to follow safety protocols, diagnose accurately, and honor warranty obligations has left me with a vehicle in an unsafe state and no corporate accountability. I've contacted their Resolutions team three times (7/2, 7/7, 7/10) with zero response.

NHTSA ID

11673763

Incident

Jun 11, 2025

On March 21, 2025, my Tesla Model 3 Long Range entered "Power Reduction Mode" — a safety feature that limits power to protect the high-voltage battery from overheating or failure. Tesla later diagnosed a coolant leak near the battery area. Their own service advisor stated in writing that the failure was “most likely related” to the battery’s thermal management system — the very system responsible for regulating battery temperature and preventing damage. Despite the connection to the battery protection system and the vehicle being under the 8-year/120,000-mile battery warranty, Tesla has refused to cover the repair. The issue remains unresolved, and I have not picked up or approved any repairs on the vehicle. My concern is that driving the vehicle in this state — or leaving this failure unaddressed — could lead to further battery damage or pose a safety risk. I am requesting that NHTSA evaluate this issue as a potential safety concern, especially as the manufacturer is refusing to repair a system directly linked to high-voltage battery safety.

NHTSA ID

11651017

Incident

Mar 21, 2025

Got into car after update, screen blacked out, could not to hard reboots. App could no longer see car. Tech support couldn't remote into vehicle or get in touch with it. Had to have it towed to service center. It's been sitting there for 6 days with no diagnosis just an estimate for $530 to troubleshoot the car. This update caused my car to completely be unresponsive and undrivable. I also had a carseat in the car.

NHTSA ID

11563092

Incident

Dec 27, 2023

The Power conversion system (PCS) failed during driving, disabling the rear motor and regenerative braking. This severely affected the driving characteristics of the vehicle, including top speed, braking profile and handling.

NHTSA ID

11556810

Incident

Nov 23, 2023

AT 70000 THE FRONT RIGHT BAR THAT CONNECT TO WHEEL WENT BAD 350 DOLLARS. AT AROUND 90000 MILES THE AC WENT BAD AND THEY SAID IS BECAUSE I USED IT TOO MUCH 4700 DOLLARS AT 110000 THE LID FOR THE CHARGER KEPT OPENING UP AND CLOSING BY ITSELF AT 127000 THE BATTERY RANGE REDUCED SIGNED WENT ON 129000 MAXIMUM CHARGE COULD BE CHARDED 47 PERCENT. AND COULD NOT BE CHARGED MORE THAN WHATEVER IS IN THERE ALREADY

NHTSA ID

11489680

Incident

Oct 17, 2022

Mileage

90,000 mi

For a growing number of Model 3 owners, components in the HV Battery Service Panel are breaking down, yet Tesla refuses to cover the repair under its Battery and Drive Unit Warranty. Specifically, the "power conversion system" (PCS) in that panel is failing, and reducing an AC charge from 48A to 32A to 16A to… zero. If an owner drives to a location to charge from a Level 1 or Level 2 charger, and the PCS has failed, that owner will be stranded, unable to operate the vehicle. I have submitted a request for mediation to the American Arbitration Association (case no. 01-22-0001-9026), but I deem it important to not only address the problem in my vehicle, but all the others experiencing this same breakdown. I am thus reporting it to NHTSA, as I purport that a recall is in order. I will attach a more detailed description of my dispute with Tesla, as well as my original Purchase Agreement with an Agreement to Arbitrate, and a copy of Tesla's most recent warranties.

NHTSA ID

11464156

Incident

Jan 1, 2022

the car tart to have sudden unintended acceleration at low speed after fully charge. The car will stop at the road Suddenly. leave car and back. The AC run for 1 min and shut down. I heard a sound which is from battery switch. 9/21, 11:15 am It happened again. I hear a sound and the car show alert. “”Pull over safely” — The autopilot system will slow down a lot passing a bride, even there is no car in the road.

NHTSA ID

11453010

Incident

Sep 20, 2021

UNINTENDED ACCELERATION RESULTING IN A CRASH WITH A TREE. MY CAR WAS TOTAL. THE CAR WAS WAS STATIOANARY WAITING TO PUT AIR IN MY TIRE.

NHTSA ID

11396564

Incident

Oct 16, 2020

Mileage

1,700 mi

CAR INTERFACE BUGGED OUT AND WOULD NOT RECOGNIZE WITH THE PHONE KEY OR KEY CARD TO START AFTER ENTERING THE PARKED VEHICLE. TOUCH SCREEN FLASHED ON AND OFF. ATTEMPTED RESETS TO NO AVAIL. SYSTEM WOULD RANDOMLY SHUT ITSELF OFF AND NOT TURN BACK ON.

NHTSA ID

11384309

Incident

Dec 20, 2020

Mileage

35,000 mi