Wilson Mot Test Centre

27/05/2026

Now that the warmer weather is here, many drivers will be reaching for that A/C button. Only to find the system not working, just like one of our recent customers found, with this lovely little Audi.

If you are having car Air-conditioning troubles, give us a call 😎

17/04/2026

One of this week's jobs on a 2010 Honda Civic

This one had been for an MOT test at another garage, failing on an Antilock Brake System malfunction.

The other garage, had diagnosed this as a faulty A.B.S. module. However, the customer wanted a second opinion and brought the car to us.

We are so glad that they did, because we have saved them from spending hundreds of pounds on a miss diagnosis.

We diagnosed a faulty wheel speed sensor causing the problem.
We then fitted a good quality replacement and confirmed the fix! 🙂

22/11/2025

One of this week's jobs on a little Hyundai i20.
The issue with this one, was a brake pedal pulse and strange grating noise, when braking.
Our experience told us this issue, was most likely caused by an Anti-lock Brake System fault.

The Anti-lock Brake System (ABS), is designed to release brake pressure to any wheel that is detected to be at a lower speed than the rest (Skidding) when braking. Then, once the wheel speed matches the rest, the brake pressure is reapplied. This operation is continuous and happens faster than you can blink.
This results in a pulsation being felt in the brake pedal, as the brake pressure is continuously changed, during a wheel lock event (Skidding).

By using sensors and tone rings with a number of teeth or magnetic segments, at each wheel. The Anti-lock Brake System, can monitor all the road wheel speeds and compare them to each other, whilst also using pre programmed data, for various different rotating speeds, due to changing steering angles.
And by using a series of electronic valves, to control the pressure of brake fluid, being sent to each of the brakes. The system can quickly overcome a wheel locking up, due to skidding, by rapidly opening and closing these valves, as required and in relation to the data from the wheel speed sensors, which are reporting the lower road wheel speeds.

As the Anti-lock Brake System is just doing it's job, it doesn't think anything is wrong. This meant, that there were no warning lights or any fault codes stored.
However, this vehicle, was clearly doing something that wasn't normal, as noticed by our customer.

This type of issue usually happens at slow speeds, when approaching junctions or roundabouts. And can be caused, by failing sensors, higher resistance in a sensor circuit, or a deteriorated or broken wheel speed tone ring.

We used the scan tool, to monitor the wheel speed data on road test, this confirmed an issue with the left front wheel speed signal. And on closer inspection, we found that the left front wheel speed tone ring, was broken.

We fitted a replacement tone ring and then carried out a second road test, confirming the fix.
No more pedal pulsing.👌

Thanks for reading till the end
Have a good weekend folks 🙂

Stevie.

18/10/2025

Another one of this week's jobs, on a lovely Nissan X trail.

This one had a stop start malfunction and engine management light on.

We diagnosed this one, as having a restricted Diesel Particulate Filter. Which resulted, in excessive exhaust back pressure, and soot content levels outside the range for the vehicle, to do it's own dynamic regeneration of the DPF, in order to clear the blockage.

This can happen because of engine management faults, or in most cases, because of constantly doing short journeys, where the exhaust temperatures necessary to burn off soot during a dynamic regeneration, are never reached. Or because the regeneration process is interrupted, by turning off the engine, or by stop start driving.
Typically, the exhaust temperature generated in the DPF, needs to be around 600°c for an extended period of 20-30 minutes, in order for the engine management system, to complete a successful regeneration and burn off the excess soot content.
It does this, by using fuel, either sprayed into the exhaust by injecting on the exhaust stroke in the engine cycle. Or by using a separate injector, mounted in the exhaust, to spray fuel directly in front of the DPF.

There was no way for this vehicle to do it's own regeneration, since the soot level was too high.
We carried out a DPF clean, to clear the soot build up. Then rechecked the exhaust pressure, to confirm the repair. 👌🙂

18/10/2025

One of this week's jobs on a lovely BMW 520d 🙂
This one had a few warnings displayed, for a pedestrian protection system malfunction.

The pedestrian protection system, can range from camera or radar activated warnings or emergency braking, when pedestrians or objects are detected in the vehicles path.

It can also include features to limit collision forces to pedestrians, by using pyrotechnic modules, within the bonnet hinges and catches, which fire when a pedestrian collides with the front of the vehicle. This allows the bonnet to pop up and act to deflect the pedestrian up over the windscreen, as opposed to through it. It also provides extra space between the bonnet and engine, acting as a crumple zone to soften the impact.

The issue on this BMW was a circuit malfunction, with one of the pyrotechnic modules, on the right hand bonnet catch.

On inspection, we found that the problem was caused by an improper repair, previously done on the wiring harness.

The wiring, had been joined by crimp and seal connectors, which were neither crimped properly, or sealed with heat. This would have given a more solid grip on the insulation, whilst protecting the connection from moisture and dirt.
Instead, the connection had been left exposed. And if that wasn't bad enough, the wiring had been incorrectly routed and was fouling the metal bracket, for the bonnet catch! 🙈

We removed the entire catch assembly, with the pyrotechnic module, then repaired the wiring.
We also used crimp and seal connectors, which were properly crimped. We also used some extra pieces of shrink tubing, to ensure a tighter seal, once the connectors were heated and sealed, since the wiring insulation isn't all that thick.
We then used harness tape, to provide extra protection to the wiring. And once the catch assembly was back in place, we routed the wiring harness the way it should have been, avoiding any fouling.

We cleared the fault codes, then made sure, that there were no more warning lights and no faults returned. 👌

07/09/2025

Here is one of our jobs from a few weeks ago, on a Vauxhall Vivaro.
The customer complaint with this one was a charging malfunction warning on the instrument panel.

We confirmed the malfunction warning, before doing a full diagnostic scan, where we discovered a fault in the Universal Power Control module, relating to an invalid Alternator link.

The Alternator, is the component which is responsible, for charging the vehicle's battery and providing power for all electrical components, when the engine is running.

Conventionally, the Alternator would have a constant output voltage of around 14 volts, regardless of the power demanded from vehicle electric systems.
This leads to inefficient charging, added wear on the Alternator and unnecessary load on the engine, which reduces fuel economy.

This vehicle, uses what is known as a smart charge system. And is the modern way of providing power for vehicle electrical systems and charging the battery.

The smart charge system, only supplies an output voltage, when the battery voltage falls below 12.5 volts, or the load on the battery is extremely high.
An example of this would be on a cold winter morning, when the heater is turned up, the lights, screen demister and heated seats etc. are all on. In this scenario, the battery voltage will drop quickly, so the smart charge system will output an increasing voltage, to increase the charging rate of the battery.

The output voltage can, in some cases reach around 18 volts, if the vehicle battery is extremely low on charge. For this reason, it is advisable, that modern vehicle's are not jump started, when they have a flat battery. The reason being, that many electrical components on the vehicle, are not designed to work with these higher voltages, which can damage them.

The smart charge system utilises regenerative charging, where it will output a higher voltage and increase charging rate, during vehicle braking and slowing down, such as when approaching a roundabout.
This creates a more efficient charging system and increases fuel economy, since there isn't an unnecessary load on the engine, during normal use.

The system is controlled via a Local Interconnect Network (computer communication) between the Alternator and another module, typically either an Engine Control Module, or a Body Control Module.

In the case of this Vauxhall Vivaro (also the same vehicle as a Renault Trafic), the Alternator shares communication, with the Universal Power Control module, this is a computerised fusebox, in the engine compartment.
The information, is then relayed on, to the Engine Control Module, which uses inputs and information from other systems, to control the charging operation and the rates of charge, of the Alternator, via the LIN communication signals.

In this scenario, the LIN communication was either missing or being corrupted, causing the malfunction warning and forcing the Alternator, in to a fixed charge rate mode.

We carried out an oscilloscope test on the Alternator LIN communication circuit, and found, that the network was displaying corrupted signals and intermittent short circuit to ground (negative).

When the Alternator was disconnected from the network, the corrupted signals and shorts disappeared, proving the fault was internal to the Alternator.

We replaced the Alternator and then confirmed the fix, using the oscilloscope. We then used the scan tools vehicle voltage display, to check the operation of the system and to make sure, that there were no more charging faults reported.👌

The video shows the oscilloscope patterns, with and without the Alternator being connected. And a closer look at a valid signal (data packet) after the repair.

Thanks for reading till the end, I know it's a lot to take in, but now you know how the system functions. 😉

Happy Sunday folks.

Stevie

16/08/2025

Here is one of this week's jobs, on a lovely little Volkswagen Polo.

The customer complaint with this one, was that the Air Conditioning wasn't working.

We diagnosed this one, as a faulty interior blower speed controller.
The issue was, that the blower didnt work on the first speed setting. This meant that there was no airflow over the evaporator inside the car, resulting in freezing of the evaporator core and pipes, which restricted the refrigerant flow around the system, as shown in the video.

The system was then shutting down the compressor, in order to prevent further freezing and damage.
However when speed setting two was selected, we can see that operating conditions are restored.

This one just needs a new blower speed controller and it will be perfect. But in the meantime, we advised the customer to use the other 3 speeds as required.

Thanks for watching
Have a lovely weekend folks!😀

03/07/2025

Hi everyone, Just a wee reminder we are still away on holiday but re open Monday 7th of July Katie’s 40th birthday 🤫🤣
Looking forward to seeing you all when we get back.

12/06/2025

Think this will be this year's winner for dirtiest cabin filter! 🤢🤣

05/06/2025

Good morning everyone, Just a little reminder of our holiday dates again. We will be closed 3 weeks today for 11days and will reopen on Monday 7th July.
If you are due your Mot or service before then give us a call and we’ll get you booked in.

Hi everyone, So it’s getting to that time of year again when we are thinking about summer holidays.
Just to let you all know WELL in advance we will close Wednesday 25th June and will reopen on Monday 7th July. If you are due a Mot or service around this time we can either book you in before or after these dates we just don’t want to leave anyone short.