The Automobile Protection association, CTV's W5 and our Consumer Specialist Lea Williams-Doherty put auto repair shops to the test.

They did an undercover investigation to see if 19 garages could properly diagnose and repair a simple problem.

The problem should have been easy to detect and cheap to fix.

The APA loosened one battery cable on two cars in otherwise perfect condition and took them to randomly selected repair shops.

A secret shopper told the garages that sometimes the cars just wouldn't start.

Of the 19 garages, only six passed the test by finding and tightening that loose cable.

The single best result in the APA's national survey came from a southeast Calgary garage.

Delta Auto Care and Repair, owned by mechanic Yadong Sun found and fixed the problem for just $30.

Two Fountain Tire shops also fixed the problem.

The one on Macleod Trail diagnosed it in the shortest time of any garage in only 30 seconds. A $134 dollar bill included a full inspection, while Fountain Tire on Northland Drive charged $157 dollars.

Midas on 32nd Street N.E. also passed the test and its bill was only $89.

The APA says that jibes with past experience, since Midas has typically been the least expensive of the chains in prior investigations.

Also earning a passing grade was the Minit Tune and Brake on Crowfoot Gate N.W.

The bill there was $180, including an oil change and tire rotation.

Canadian Tire on Shawville Way also found and fixed the problem for a total of $213.

But these were only six garages out of 19 that properly diagnosed and fixed the loose cable.

The other 13 either couldn't figure it out, or worse, performed and charged for unnecessary repairs.

Four couldn't find the problem, but didn't do any unnecessary work.

Of the remaining nine, three recommended unnecessary work and six actually performed and charged for unnecessary repairs.

Canadian Tire at 3516 8th Ave. NE charged $507 to replace a perfectly good battery and two perfectly good spark plugs.

When the secret shopper asked the garage to return her original plugs, the shop gave her plugs from a different car.

"APA's spark plugs were about 1000 km old. The ones they gave back were spark plugs that were about 80,000 km old," says the APA's George Iny.

The Canadian Tire in Country Hills had the second worst result.

It charged $407 to replace a good battery.

The mechanic initially indicated the battery was "satisfactory" on the inspection form, but someone later crossed that out and marked "unsatisfactory".

"So we have the sense there that it's not the tech working on your car that makes the final decision. Someone in the shop might decide "hey you know, we gotta put some parts on" for one reason or another," says Iny.

For comment on these two failing results, we were referred to a vice president at Canadian Tire.

She provided an emailed response. In it she states that Canadian Tire is "...committed to operating with integrity... At no time was the mystery shopper told that recommended work was required when it wasn't...Canadian Tire is fully accountable to our customers and in any case where a customer has questions about the work done on their vehicle, we will be transparent and responsive."

Kal Tire on Edmonton Trail found and tightened the loose battery cable.

Problem is, it also replaced the ignition switch for a total of $355.

When contacted, Kal Tire maintained that the ignition switch core was loose, and because battery problems typically don't cause the "intermittent no start" trouble described it was reasonable to replace the switch.

The Kal Tire on 42nd Avenue also got it wrong, replacing the car's battery for $171.

Kal Tire stands by that as well, stating that because the battery was unlabeled, its tech had to guess at the baseline number for a passing grade on the battery test and the battery failed based on the numbers used.

The Fountain Tire on 40th Avenue also failed, needlessly replacing the car's battery.

The bill totalled $233.

The shop's owner, Rick Ball took full responsibility and offered a refund.

"The buck stops here. I'm the guy that's responsible and we did it wrong."

Ball said it was either human or equipment error and replaced his battery testing equipment to prevent future mistakes.

The owner of Calgary's Midas shops also took responsibility for the failure at 16th Ave. NW. That shop unnecessarily replaced the car's battery for $187, based on erroneous battery test results.

In a written statement, he said "the technician relied on the electronic testing tool for the battery test results and missed the loose battery terminal connection. The battery terminal should have been checked...we have since then replaced the testing tool."

He pointed out that unlike some garages Midas does not pay its employees commission on parts sold to remove any incentive to oversell.

Consumers have to look out for themselves to avoid paying for unnecessary work.

There are a couple of things anyone can do.

"I would start with my owner's manual. So if it says I should be doing things at a certain mileage, that's when I do them, not when someone says "your fluid is dark, you gotta change it," says Iny.

He also recommends a second opinion before authorizing expensive repairs you weren't expecting.

Shops that failed the APA test:

Midas: 624 16th Ave NW

Canadian Tire: 3516 8th Ave. NE

Canadian Tire: 388 Country Hills Blvd. NE

Kal Tire 3712 Edmonton Trail NE

Kal Tire 404 42nd Ave SE

Fountain Tire: 425 40th Ave NE

Shops that passed the APA test:

Fountain Tire: 7007 MacLeod Tr.

Canadian Tire: 250 Shawville Way SE

Minit Tune & Brake: 152 Crowfoot Gate NW

Midas Auto Service: 3378 32nd Street NE

Fountain Tire: 4911 Northland Drive NW

Delta Auto Car and Repair: #206, 255 28th Street NE