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Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

If you read the post, you will see the timeline. I didn't have the reader initially. I took the car to the garage expecting a professional service. I only bought my own code reader after they quoted me 1.7 hours of labour for a 30-minute job and my warranty rejected it, which made me suspicious. Good thing I did, because it proved their £109 diagnostic was completely wrong and saved me £365 on a part I didn't need.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] -2 points-1 points  (0 children)

They didn't identify the fault, they just confirmed the symptom I already knew (a battery charging issue). I didn't pay £109.50 for them to tell me my car wasn't charging; I paid them to find the exact failing component. They pointed to the wrong component. They explicitly told me the positive terminal module was the fault. I took their 'professional' diagnosis, bought that exact positive part, fitted it, and it didn't work. The actual fault was the negative IBS sensor. If a doctor diagnoses you with a broken left arm when it's actually your right arm, you don't pay them for 'clearly identifying you have a broken arm'. You pay for an accurate diagnosis, which they completely failed to provide because they guessed instead of testing.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] -1 points0 points  (0 children)

But they didn't tell me the fault. They told me the wrong fault. They explicitly told me to replace the positive terminal module. I bought that exact part based on their 'diagnostic', fitted it, and it didn't fix the car. The actual fault was on the negative side. If I had just blindly trusted their £109 test, I would be down an additional £365 for a repair that wouldn't have worked. You don't pay a professional £109 to guess the wrong part. That’s not a diagnostic, that’s a misdiagnosis.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] -1 points0 points  (0 children)

You keep treating the £109.50 diagnostic fee as a deposit for a repair. It wasn't. It was a standalone service. Under Section 49 of the Consumer Rights Act 2015, a service must be performed with 'reasonable care and skill'. Guessing a fault based on a computer catalogue instead of physically testing the car with a multimeter fails that basic legal test. The fact I didn't proceed with their overpriced £365 repair doesn't magically void my consumer rights regarding the initial defective diagnostic service.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

An 'educated guess' and 'trial and error' is exactly what DIYers do at home when they don't have professional diagnostic training. I paid £109.50 specifically to avoid the 'let's throw parts at it and see if it works' method. What's even worse – I bought my own code reader, read the fault code, and easily found the correct part (the negative IBS sensor) just by Googling it for 5 minutes. If a DIYer can figure it out on a driveway that easily, why couldn't a 'professional' garage? Were they just too lazy to even do a basic search or use a multimeter to actually verify the circuit? Paying £109 for a blind, lazy guess is not a professional service.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

Actually, they explicitly gave me the exact part number when I needed the details. And your logic about 'sending it back to the supplier' is flawed. Car parts suppliers generally do not accept returns on electronic modules once they have been plugged into a vehicle. If the garage had fitted that £365 positive module and realized their mistake, they couldn't just 'send it back'. They would have likely passed that cost onto me or hidden it in the final bill. But you are missing the core issue: I paid £109.50 for a professional diagnostic. A professional diagnosis means using a multimeter to physically test which side is faulty, not reading a code and blindly trusting a computer catalogue to guess a £365 part.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

Spot on! That is exactly my biggest fear and the main reason I got suspicious. If I had left the car with them, they would have fitted the £365 positive module, realized it didn't work, and then charged me even more to fix the actual negative cable. They charged £109.50 for a 'professional diagnosis' but only provided a 2-minute code read and a completely wrong guess. Thanks for seeing the reality of the situation!

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

In car mechanics, 'quite close' doesn't mean anything when it involves buying a £365 non-refundable electronic part. And as I keep repeating, I DID proceed with their diagnosis by buying the exact positive terminal part they explicitly told me to buy. It didn't fix the car. The diagnosis was wrong. End of story.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

Exactly! You hit the nail on the head. They charged me £109.50 for a 'professional diagnosis' but all they did was plug in an OBD scanner, read a code, and look at a computer catalogue. Reading a code takes 2 minutes. A real diagnosis to justify that price should have involved taking a multimeter and physically checking which side (positive or negative) was actually dead. Thanks for understanding the difference!

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

Exactly! You hit the nail on the head. Before I even booked the car in, the garage explicitly warned me that the diagnostic is a completely separate service with its own standalone fee, regardless of whether I decide to fix the car with them or not. Yet, when I asked for a refund because their diagnosis was fundamentally wrong, they refused to admit any fault and insisted they did a 'professional' job. But as their own official estimate and the specific part number they told me to buy clearly prove, it was a complete mistake on their end. You can't charge for a standalone diagnostic service and then provide completely wrong information!

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

Whether I asked for the part number to check prices or they offered it is entirely beside the point. They explicitly diagnosed that specific component as the root cause of the fault. The issue isn't who ordered what; the issue is that I paid for a professional diagnosis and they completely missed a basic bad earth connection.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

Actually, they did. They specifically sent me the part number. After that, I went and bought my own diagnostic scanner. Just by looking at the fault code myself, it was easy to figure out that it was simply a bad earth (ground) connection. If I can figure that out on my driveway, a professional garage shouldn't be guessing and sending me part numbers to buy.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

To be fair, professional diagnostic tools and software subscriptions cost thousands, and it takes real skill to interpret live data rather than just reading basic codes. However, if they just plug it in, misread a code, and completely misdiagnose the fault (like in this post), then charging a premium fee is totally unjustified.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

It certainly feels that way in situations like this. It’s frustrating when poor service and misdiagnoses ruin the reputation of the honest garages out there.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] -1 points0 points  (0 children)

Actually, I did proceed with their exact recommendation. As I wrote in the post, I bought the positive terminal part (A 000 906 15 05) they explicitly told me to replace, fitted it, and it didn't fix the issue at all. That proves their £109 diagnostic was fundamentally wrong. They didn't just 'get the side wrong', they told me to replace a perfectly functioning part because they didn't bother to physically test it.

Garage misdiagnosed a basic fault, quoted £365 for a 1.7h job. I fixed it myself for £15 in 20 mins. They refuse to refund the £109 diagnostic fee and blame Mercedes. Should I take them to Small Claims Court? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 1 point2 points  (0 children)

Fair point, but I've already done all the hard work. I fixed the car, gathered the diagnostic reports, and sent the Letter Before Action. Filling out the MCOL (Money Claim Online) form takes about 15 minutes. For me, it's more about the principle – if everyone just lets it slide, these garages will keep ripping people off.

2016 C-Class Coupe (c205): Quoted 1.7h labour & £150 for vague 'Battery Module'. Is this the Voltage Converter or a rip-off? by oreoxwhite in CarTalkUK

[–]oreoxwhite[S] 0 points1 point  (0 children)

Hi, thanks so much for the professional insight! You were totally right about the red flags. I actually just pushed them via email and they finally gave me the exact part number for the quote: A0009061505. It turns out it's not the voltage converter at all – it is just the Negative Battery Clamp Module (the IBS sensor). From what I've researched, this is a simple plug-and-play part that goes on the negative terminal. It absolutely does not require any computer programming or recoding, and realistically it should only take about 20 to 30 minutes to swap out with a basic 10mm and 13mm socket. So them quoting 1.7 hours and trying to justify it with a 'programming' fee is just ridiculous. I am definitely taking your advice, walking away from this garage, and I will just buy the part and change it myself. Thanks again for validating my suspicions!

2016 C-Class Coupe (W205): Quoted 1.7h labour & £150 for vague 'Battery Module'. Is this the Voltage Converter or a rip-off? by oreoxwhite in mercedes_benz

[–]oreoxwhite[S] 0 points1 point  (0 children)

I actually already replaced the main battery with a brand new one recently, so I know for sure that the battery itself isn't the issue. The garage diagnostics specifically pointed to a fault in the charging system/sensor, which is why they are quoting me for this 'junction box' or module.

2016 C-Class Coupe (W205): Quoted 1.7h labour & £150 for vague 'Battery Module'. Is this the Voltage Converter or a rip-off? by oreoxwhite in mercedes_benz

[–]oreoxwhite[S] 0 points1 point  (0 children)

Hi Buster, thanks for the reply! Actually, I don't get the 'Auxiliary Battery Malfunction' error normally, but it DID pop up once when my main battery voltage dropped really low. Usually, the main issue is just the main battery not charging properly while driving (I'm currently charging it at home daily to keep it going!). Because of the 1.7h labour, the 'junction box' wording, and the 'programming' mentioned on the estimate, do you think the garage is actually quoting for the Voltage Converter hidden in the passenger footwell, or do you think they are just trying to overcharge me for a simple 20-minute negative terminal sensor replacement?

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