The company failed to fix 11 out of 20 defects deliberately left by Trading Standards.
An illegal Vauxhall Astra with broken or missing light bulbs, irregular tyre pressures, oil leaks and faulty windscreen wipers was sent to the Halfords Autocentre in Filton, Bristol by South Gloucestershire Council for a major service at a cost of £235.
Lee Reynolds, for the council, told North Avon Magistrates’ Court: “It became obvious that not all the checks were done.
“Things were ticked as having been done that had not been and the consumer was not made aware (of the defects).
“This is a national company. A consumer puts a lot of trust and faith in a national firm to do a proper job to ensure a car service is conducted thoroughly and professionally and in these circumstances it was not.”
Halfords pleaded guilty to eight counts of breaching consumer protection laws and the technician, who carried out the service, resigned.
Reports suggest the investigation was sparked by a rising number of complaints about the car industry in Bristol.
Magistrates fined the company £32,000, ordered them to pay £14,862.04 costs and a £120 victim surcharge.