"The preliminary investigation indicated that the man drove into the car wash and for an unknown reason, tried to exit his vehicle," police said in a statement.
"The vehicle then rolled forward, pinning the man between the car and the machinery."
Investigators said it did not appear that the car wash had been activated at the time of the accident.
Officers managed to lift the car and free the victim before attempting CPR; he was rushed to Palomar Medical Center, but pronounced dead there.
The 24-hour business has no on-site staff, and has both automated and self-service stations; The automated side — where the victim was found — does not use conveyor belts, but rather prompts the driver to move their car themselves when instructed.