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Testing ignition start switches

RollCo, specialists in rotating electrics and engine management products, examines how to tackle faulty ignition start switches.

Faulty ignition starter switches are common on Vauxhall/Opel models as well as many other makes of vehicle. A faulty ignition start switch results in a permanent electrical feed to the starter solenoid “s” terminal. This problem can result in the starter motor being ‘held in mesh’ while the engine is running, known as ‘over-run’. 

3 simple steps

There is a simple three-stage process for checking if the start switch has failed. Firstly, check the armature shaft and if the drive pinion is showing evidence of heat damage or heat discolouration. Next, does the starter motor or solenoid smell burnt? If it does, there’s an issue. Is there any pinion damage or ring gear damage? Again, this is a tell-tale sign that the starter switch has failed or is faulty and needs to be replaced.

Next up you have to tackle any electrical issue on the control circuit. However, there is a very quick and easy way to do this and all you need is a 12V test lamp or Volt Meter.

Tips for checking the control circuit:

1. Remove the lead from the solenoid switch terminal and connect a 12V test lamp or Volt Meter on the wire, switch to crank position and the lamp will light

2. Release the key

3. If the lamp stays on, replace the switch

It’s a simple test, but will ensure your diagnosis is correct. When replacing, make sure you choose an aftermarket manufacturer, such as RollCo, which supplies OE standard products, giving you and your customer peace of mind.

For more details on RollCo’s product range visit

About Autotechnician
Autotechnician is a magazine published nine times a year, delivering essential information to independent garage owners and technicians in the UK. Delivered both digitally and in print, autotechnician provides readers with technical, training, business advice, product and news, allowing our readers to keep up to date with information they need to run and work within a modern workshop.
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