Mensa

Hi, Thanks again for the reply. The radar was something I added about 3 years ago, and it has been working fine up until now. I tested the earth with an ohm meter as you suggest, and it registered ZERO. The reversing light earth wires on my car are green/yellow. They bolt to the body just inside the boot, by the inner wheel arch. They are tight and working properly. There is only one reversing light on my C3 Pluriel. Fuse F1 only feeds this light, nothing else. I have removed it and it is fine. However, the original problem still persists. With a bulb in the reversing light, neither light nor radar works. With bulb removed the radar works. With a 5W bulb instead of the 21W, both radar and light work, but the light is so dim that it cannot illuminate at all really - and then sometimes it doesn't light at all and the radar fails too. The bulb holder terminals are perfect too, so I'm still struggling to understand what can be wrong.

Hi, That was really good advice. I was testing it with another new 21w bulb, unsuccessfully, but have now tried it using a 5w bulb and everything works. However, the reversing light is now very dim, as it should really be a 21w one. This is a great short term repair, but do you have any idea of what is at the root of the problem? Many thanks.

Many thanks for the quick reply. I have attached a wire from the bulb to earth, but with the ignition on and the gearbox in reverse there is still no light or radar working. As soon as I remove the bulb the radar starts working, and the bulb holder has 12v through it. (I don't know what voltage is in the holder when the bulb is fitted, as there are no terminals visible.) So the switch does work, although maybe when the bulb is fitted there is too much current for it. Do you think it is a good idea to test the gearbox switch by shorting across its terminals - the reversing light and radar should be on permanently then. Providing I can find the switch, that is! Do you know where it is?

Hi, My C3 Pluriel (Sensomatic gearbox) reversing light and radar have stopped working. I have done the following tests: With reversing bulb fitted, neither light nor radar work. With new bulb the result is the same. If I remove the rear reversing bulb, with gearbox in reverse, the radar works and there is 12v at light connector. If I remove the rear reversing bulb, with gearbox in neutral, there is 4v at light connector. If I remove the rear reversing bulb and remove the radar, with gearbox in reverse, there is 12v at light connector. If I remove the rear reversing bulb and remove the radar, with gearbox in neutral, there is 11v at light connector. I believe the gearbox sender cannot take the power of the bulb without shorting out, but can take the power of the radar on its own. If this is the case, I need to find the gearbox sender so I can test it. Please could someone tell me EXACTLY where it is and what it looks like? Many thanks, Andy.