acw285

OK, we have reverse lights! And here's how: To test if the switch is at fault without having to reach it, take the cover off the engine bay fuse box, form a link with a short length of wire between terminals 2 and 4 on the black 16 pin connector. Just poke the ends of your wire in beside the red and violet wires, don't take the connector block off or the wires out. Switch on ignition (but not the engine) and engage reverse gear. Take a look see if the reverse lights have come on. If the lights are on (as they were in my case), the problem is the switch. If they are still off, the problem is either fuse 1, the BSI computer (in the glove box), the bulbs, corrosion on the bulb terminals (one of mine was corroded very slightly and not working) or your link has fallen out. The Haynes manual tells you to test with a multimeter set to resistance. This was the very first thing I did, but because the meter only showed a small amount of resistance (200 ohms) when reverse was engaged and infinite resistance when disengaged, I thought the switch was OK. That's what sent me on a day long fruitless search for another cause. A new switch has no resistance with reverse engaged. To replace the switch: The Haynes manual tells you on page 7A.5 to remove the air cleaner assembly and inlet ducts. Looking at the pictures of the engine bays on page 0.11, I can see that this is necessary for petrol engines, but for diesel engines like mine, you can see the switch poking out of a hole on top of the transmission casing to the left of the battery without having to remove anything. Diesel owners only have to remove an air deflector (forward of the battery and a cinch to remove) and an air duct elbow which is clipped in on the right and pulls out on the left. The switch can be identified from photo 5.5 on page 7A.5 of Haynes. The grey wiring connector is easy to remove by hand only if the clip is pointing straight upwards. As the thing is screwed in, it could end up pointing in any other direction. If you can't do it by hand, you'll need to make up a hook out of a piece of wire. I used some 1/16" diameter welding wire forming it into a tall 'u' with a flat bottom and bent the two tops 90 degrees to pull it with. There are plenty of other similar connectors around the engine to practise on. You'll need a deep 22mm socket (£6.49 from Halfords) and an extension or a long box spanner. The switch itself cost £5.49 from the local Citroen dealer. Then it's just like changing a spark plug. You don't need a new washer. Hope that helps someone. Adrian

I've compared the input and output voltages to the BSI of the brake lights (which work) and the reverse lights (which don't). Brake lights: about 12 volts in and 12 volts out. Reverse lights: about 200 millivolts in and about 120 millivolts out. Not enough to impress a bulb. So, when it's light again I'll do a voltage test either side of the reverse light switch which seems now to be the most likely culprit. I'll post the results. Adrian

Thanks for your prompt reply, kfk. I should have looked at the wiring diagram before I posted my message to remind myself what I actually did check. I did check Fuse 1 (and MF7) and the ohmmeter went between terminals 2 and 4 on the black 16 pin connector with fuse 1 removed to check the gearbox switch. I have also reset the BSI several times as per the instructions on the BBA-reman site. Cheers Adrian

Hi The reverse lights on my 53 reg C3 don't work. From this week I'll be reversing down our lane in the dark when I get back from work. Both bulbs are OK, as are the fuses, the earth path and the switch on the gearbox. I checked the switch by taking out Fuse 7 (if I remember), putting an ohmmeter between one of the fuse holder terminals and earth and asking my daughter to engage and disengage reverse a few times. That saved removing tons of stuff to get to the switch. I know that the signal from the switch goes to a computer which will then switch on the lights. (Why don't they do that in houses?) Now, when my windscreen wipers and washers all packed in, I eventually discovered through trial and error that the reset code involved putting on the 'see-me-home' lights and then operating the wiper switch. (Can offer more details if anyone wants them.) Does anyone know the reset code for the reversing lights, please? Adrian