Diagnostic Case study


Car make: Volkswagen

Car model: Scirocco

Year: 2012


The customer called us with his Volkswagen Scirocco in a non-start condition. The vehicle had been to 3 garages before he called us and one identified a fuse blowing but were unable to establish why, they found that disconnecting the glow plug wires allowed the vehicle to run and the fuse not to blow, they suggested replacements of the glow plugs but could not offer a 100% chance of fixing the problem.

With the dilemma of paying for replacement parts that may not fix the issue, the customer opted to seek further advice.


We spoke in detail with the customer as we do on all our diagnostic or fault-finding jobs, this allows us to know as many details as possible about the nature of the fault. We gained authorisation from the customer to investigate the fault. We identified the fuse that would blow and the circuit is protected. Armed with this information we consulted the manufacture wiring diagram and were able to see the circuit in detail. We proceeded to disconnect the glow plug wires but couldn’t replicate the fuse blowing or the engine cutting out. However, we could replicate the customer complaint by manipulating the wiring harness close to the glow plugs.

The fault would occur when doing this because the wiring loom had previously been left insecure and had been chafing on the engine block, ultimately resulting in exposing bare wires and shorting out, causing the fuse to blow and the car to cut out. The reason it would improve when disconnecting the glow plugs is that by doing so, it allowed the wiring loom to move slightly and move away from the engine block and not cause a short circuit.

Without access to and correct understanding of manufacture wiring diagrams and information would result in incorrect diagnosis and replacement of unnecessary parts, causing unnecessary expense to the customer. Our skilled technician repaired the damaged section of the wiring and correctly secured it to ensure a repeat doesn’t happen.

Customer feedback:

I was thrilled by the service received at UNR automotive. They were professional and transparent throughout. I had been to 3 garages prior and was faced with the prospect of spending large amounts of money without a guaranteed fix.

UNR Automotive kept me informed throughout and authorisation was sought at each stage. The total cost of the diagnosis and repair was less than I had spent at the previous 3 garages combined, a true value for money service by a professional garage.

Diagnostic Case Study

Any questions?

If you have a question that’s not answered below, simply give us a call, we’re always happy to help with advice.
Scroll to Top