The heating system at Crystal Peaks Market has been out of action since the end of last year and although a replacement is due to be fitted next month, many traders feel something should have been done sooner.
The matter came to a head when a plug on one of these heaters blew, leaving the socket scorched and what one stallholder described as a 'fishy smell' wafting from the partially molten plastic.
Sheffield Council, which manages the market, said the fault was quickly resolved, all heaters had been tested and safety was never compromised.
Julie Roden, who runs a haberdashery business there, said: "They take the service charge but we're not getting the service.
"Customers have noticed the market's decline and asked what's happening. Since the new market opened down The Moor we feel we've been forgotten even more."
The council's markets manager Louise Pearson claimed there had been significant investment in the last year, with money spent revamping the entrance, brightening up the interior and promoting the market.
In the coming year, she added, new LED lighting is due to be installed, the men's toilets are in line for a much-needed renovation and there are plans to hold more events there to attract new customers
She apologised for the delay in fixing the heating, but said this was because it had taken time to secure council funding for the work so the £200,000-plus cost would not have to be passed on to traders.
"I know some traders at Crystal Peaks feel like poor relations to those at The Moor Market," she said.
"We work hard to offset that, but they're not in the city centre and there's nothing we can do about that.
"They get exactly the same amount of time from the markets team. There's always a security guard on site and on most days there's also a member of the markets team present.
"If traders do have concerns, we have regular meetings and they can always come and talk to us."
WHAT THE TRADERS ARE SAYING
Butcher SHAUN EMSON, who has been there for 23 years, said: "The condition's gone down and down in the time I've been here because they're not investing enough in the upkeep."
SHAUN PINDER, who has run a schoolwear stall at the market for 30 years, said: "It's shocking. I don't think they're taking much notice of us. We always seem to be playing second fiddle to The Moor Market.
"Not only is there no heating or air conditioning, you've got lights out, the toilets are a mess and we still have the same flooring as when I arrived."
MARIA TIMMINS, who runs a video game stall, pays £650 a month in rent and service charge for each of her two units but feels she gets little in return.
"You know something's wrong when you're wearing more clothes at work than you need outside," she said.
"If you look at the market, it's falling apart. You don't get anything done here unless you stamp your feet."
JULIE RODEN, who has been at the market for 24 years, claimed footfall had fallen substantially in recent years, with her takings down by a third in each of the last two years.
Not all the stallholders were unhappy. WAYNE RHODES, who opened the Karnivore BBQ food outlet three months ago, said it was thriving and the market managers had done 'everything we needed'.
Despite traders' concerns, most customers declared themselves happy with the state of the market, praising the convenience of access, friendly atmosphere and the bargains to be had.
While footfall is around five per cent down on 2017 so far this year, she blamed this on a tough start to 2018 for retailers in general - not helped by the recent snowy conditions - and said more than 30,000 people had still visited the market in just one week earlier this month.
The occupancy rate of 87 per cent, meanwhile, is due to rise to over 90 per cent once two new double units being fitted out as a children's clothing store and a jewellery retailer open in the coming weeks.