I’ve got a 2008 Mk3 which has been giving intermittent alarms for quite a while and decided that I need to do something about it. Seems the most common culprit is the bonnet microswitch so will start with that. Does anyone know if it is possible to get a replacement microswitch or does it have to be a complete latch assembly?
Thanks
Easy check here.
Open and secure the bonnet, unplug the switch connector from the loom, and test switch continuity at this connector;
. the switch should pass current from your multimeter with bonnet open.
Leaving the bonnet open, use a screwdriver to lock the catch,
. and now the switch should be open with no current passing.
Now immediately UNLATCH that catch before doing anything else, such as trying to close the bonnet!!! (It gets expensive if closing the bonnet onto a latched catch.)
Usual causes of non-mechanical problems are:
. salty water in the connector,
. salty water getting into the microswitch.
Results because of salt can be:
. bad connections all round,
. and/or current leakage.
Possible cures if just contaminated and nothing actually broken:
. copious clean warm water to rinse it out (squeezy bottle helps),
. then Servisol Super 10 contact cleaner inside switch and connector followed by exercise of contacts,
. and finally WD40 on the outsides to waterproof it and keep out the salt.
A replacement microswitch should be the same size and rating and with the same attachments in order to fit and handle the work.
Be careful.
Mobile phone left in the car? Guaranteed to set off the alarm somewhat randomly.
Think I can discount that as it can happen at any time day or night and no phone or other device anywhere near.
Thanks for your input and quick replies.
Thanks for your quick responses.
As the fault is intermittent and could go a few weeks without alarming, I thought it may be a bit uncertain even if the switch does appear to check out OK.
I was hoping that by replacing just the microswitch I might be able to either eliminate that as a cause, or if at sometime in the future it alarms again I can start looking at other possibilities.