People living near the site in New Road, Willenhall say it is a noisy neighbour and a safety hazard.
Walsall Council rejected a second application for a car wash on the site on January 31, having already turned one down in May last year, amid concerns over increased traffic and residents being disturbed.
But the business remained open at the weekend prompting residents to urge the council to take enforcement action against the owner.
A worker at the car wash, who would not give his name, said they would be appealing as they believed it was a suitable business for the site.
But Councillor Diane Coughlan said residents have had enough of living opposite the car wash, which has been open around two weeks.
"I've been contacted by residents who don't want to live by a car wash. Planning permission has been refused and it should no longer be operating. We want people to follow the rules.
"There are concerns about traffic because it's a busy road and the main thoroughfare from Wolverhampton to Walsall," she added.
Irene Haynes, aged 70, who lives across the road from the car wash, said: "I don't think it should be here.
"Not only has it not got planning permission but it has also been refused planning permission. Who wants to live opposite a car wash?
"I think MPs need to be looking at planning regulations to ensure this can't happen. If something is refused planning permission that should be the end of it."
Her husband William, 72, added: "It's not right that they don't take any notice. They've been told no. This is a main road and it's not a suitable business for this area."
Derek Holmes, 80, who also lives a stone's throw from the car wash, claimed spray from the water regularly covers the road and footpath in Wolverhampton Street which runs at the back of the car wash.
While Linda Harvey, aged 63, said signs advertising the car wash were often placed on the pavements. "It's an obstacle for women with pushchairs or people in wheelchairs – it could be dangerous," she added.
Walsall Council planning officers refused the application saying it would lead to increased traffic queuing on a road that was already busy.