A car service sting by trading standards found "multiple failings" at a Halfords Autocentre site and led to fines and costs totalling almost £47,000.
Technician Alex Tovey at the Halfords Autocentre workshop in Filton failed to spot or fix 11 of 20 defects which South Gloucestershire Trading Standards officers had rigged onto a Vauxhall Astra before sending it in for a £235 service.
They had taken the action after a rising number of complaints about the motor industry in the area.
North Avon Magistrates Court was told all the defects should have been picked up during the major service. The failures included not checking or replenishing the brake fluid, broken or missing lightbulbs, faulty windscreen wipers, oil leaks and irregular tyre pressures.
Halfords Autocentre pleaded guilty to eight charges under consumer protection laws and was fined £32,000, plus costs of £14,862 and a £120 victim surcharge.
Halfords Autocentre said in court that an internal audit had revealed earlier shortcomings at the branch,
Tovey left the company four days after the trading standards sting in March 2014.
In its defence, it said the issues undiscovered were not “overtly dangerous” and its technician had identified two faults the trading standards engineer was not aware of.
The sting had also occurred a month after the company had rolled out a new operating manual, which affected paperwork and its quality control procedures. Improvements had been made since.
After the case, Halfords said: "We are deeply disappointed that in this case we did not meet the very high recruitment and training standards we set ourselves.
"We immediately launched an internal investigation and are confident that this is an isolated case."
Halfords operates over 300 Autocentres throughout the UK, employing over 2,000 people and working on approximately 60,000 vehicles per month.