Reversing Proximity Sensor

[Ellis]

Hi, I have a C5 3L Diesel Exclusive. It is factory fitted with proximity sensors and a screen read-out on the dash, presumably to assist in parking etc. I find there is a problem using this system in that it lulls you into a false sense of trust in the system. When moving forward, either with a forward motion gear selected, or in neutral free forward motion, the front proximity sensor operates as one would expect. However when using the system for reversing you need to be very alert. If you reverse down a slight grade and begin the motion by selecting reverse motion then move the selector to neutral so you can have gentle and controlled braking at very slow speed, the proximity sensor system TURNS OFF!!!...and kapow!!...you hit any object behind. You didn't expect this, because the behaviour of the system when reversing is DIFFERENT from the behaviour of the system when moving forward!!..how stupid is that!!

[paul.h]

Welcome to the forum.

 

The reversing sensors are only switched on when the gear lever is in the reverse position so when you put the gears in neutral you are switching off the sensors and the screen display will also switch off. This is the same with aftermarket sensors which are usually tied in to a reversing light wire. What you need to do is dip the clutch pedal instead of using neutral, this will also keep the reversing lights on to warn others you are reversing and if dark will light up the back so you can see.

 

If you have found this out by hitting something I hope it was not too expensive to fix.

[Ellis]

Thanks Paul. Still a bit miffed though...dunno why they didn't make the rear sensors work the same as the front ones, that is, NOT switched off when you are in neutral...my car's automatic, so it's even more of a bugger...when you are backing down a slight grade, you DON'T want the car to be in gear to make the sensors work...you want it to just coast so you can have good control, yet have the sensors ON so you can see the low trailer you're about to hit.....(yes, I found out by hitting a trailer)

[paul.h]

Maybe you could have a look at the wiring in the boot and see if the sensor system takes a feed from a reversing light - if so you could try linking in a 12 volt feed with a switch on the dash so you could switch it on when not in reverse (it may also put on the reversing light). Another possibility is to provide a switched earth at the reversing switch on the gearbox (if the auto has one).

[Ellis]

You're on to it Paul....yep, makes very good sense...any proximity sensor should operate at ALL times the ignition is on...by definition, that's what a proximity sensor is...something to tell you of any object within close range, so you are aware. I'll look for a way of making this happen. To be honest, I'm a bit disappointed in Citroen for this....I also have a Mercedes Vito 8 person people mover, and its proximity sensors ALL work ALL the time the key is on, whether you're in neutral, park, drive, or just eating a scone. Just very jolly sensible. By the way, if any of you out there want to make your late model C5 ride better than the pogo stick pitchy ride they come with as standard, let me know.....I've experimented and got mine running pretty much as smooth and flat as my Xantia did...involves using green spheres though...

Edited June 24, 2015 by Ellis