I am looking for a reversing light switch for a Marea 1.6 2001, but there seems to be two different parts. They have different thread size: 18 mm and 14 mm. Which one is correct for my Marea?
Could it be so that the thread size in the gearbox housing was changed during 2000-2002? And why..? If it was earlier M14, why did they change the size to M18?
It is odd, the switches appear quite different in length and design, so I suspect the gearbox it's self has been revised.
So it may be a good idea to inspect your old one before ordering.
I have often been supplied wrong parts by companies, sometimes due to the staff not bothering to check if there is an option, it's annoying as the labour and hassle if a car is immobilised in a workshop for example can be great.
Before I retired I always told my parts supplier that if there was an option to send both and they would collect the unused item on their next delivery before billing my account. Obviously not an option generally, but I had traded with the company since the 1970s.
I took a picture of it. It was a little difficult because of poor lighting, and I could only use a small torch, and the exposure time was 0,25 s, but nevertheless it is quite a good shot. Doesn't it look like the nut is a little cracked..? Anyway, it looks like the M14 switch.
In fairness I don't think it looks much like either.
If you are sure that is the reverse light switch , why don't you take the plug off it and bridge the two wires safely , then with ignition on reverse lights should work, just to prove it is the switch, then I would unscrew it and measure to be sure what type , refit but leave disconnected electrically as not working anyway and order the correct switch.
That would be the best method, but getting access to the front of the gearbox is a little laborious because of the engine splash which has to be removed, and before that you have to jack up the front of the car and remove the front wheels... and then doing it again...
It could also be this M18 one. There are several spare part manufacturers each having their own idea of what a part should look like. Who knows who manufactured the original one.