C5 suspension height glitch

dnsey · Unread post by **dnsey** » 27 Feb 2011, 10:37

I removed a heavy load from the boot of the C5 this morning, which had been standing all night, and heard the suspension pump running for about two minutes. Was about to pull the fuse to ensure that the motor didn't overheat, when the pump stopped and I noticed that the front was on maximum height, but the rear was on normal.
Did a Citrobics session, and it became clear that the front suspension would go to max or min, but nowhere in between. Out with the axle stands to examine the height sensor, which looked fine, and seemed free (the dogbone connector, similar to earlier height correctors, was still in place too).
With thoughts turning to the expense of a Lexia session, I thought it might be worth doing a system reset first. Disconnect battery, discharge across leads, reconnect, wait while the system boots (trying not to panic about the 'immobiliser fault' message in the meantime

All OK, suspension behaves normally at all levels!

Thought this might be worth posting in case anyone else has the same issue

Citroenmad · Unread post by **Citroenmad** » 27 Feb 2011, 13:54

It obviously got a bit confused for some reason!

Did you try and drive the car to see if that would have sorted it out?

P616VKX · Unread post by **P616VKX** » 27 Feb 2011, 14:04

If only it was so simple on the Xantia!!!!

dnsey · Unread post by **dnsey** » 27 Feb 2011, 14:45

Did you try and drive the car to see if that would have sorted it out?

Yes - and bouncing it, jacking it up, etc.

If only it was so simple on the Xantia!!!!

Ah, but the C5 has this in addition to the usual Xantia problems (or their equivalent)!

Citroenmad · Unread post by **Citroenmad** » 27 Feb 2011, 14:56

Hmm in some ways the C5 is a simplified , if more computer based, car as far as its suspension goes. Generally C5s suspension is good and reliable.

Still, you have not had to actually spend any money or do much, apart from disconnect the battery. Thats not bad!

wheeler · Unread post by **wheeler** » 27 Feb 2011, 17:26

You could swap the body height sensors around, if i remember right they are both the same but just fit different ways round. If the fault maove to the rear then it looks like a faulty height sensor.

cachaciero · Unread post by **cachaciero** » 28 Feb 2011, 14:44

Citroenmad wrote:Hmm in some ways the C5 is a simplified , if more computer based, car as far as its suspension goes. Generally C5s suspension is good and reliable.

Still, you have not had to actually spend any money or do much, apart from disconnect the battery. Thats not bad!

Pity they did'nt / haven't and now probably won't do the development to the next logical phase. i.e position feedback on each strut together with a raise and lower valve for each strut, that with the right software could have made anti roll bars redundant and turned Activa owners green with envy

cachaciero

dnsey · Unread post by **dnsey** » 01 Mar 2011, 19:19

Ah well...it's never as simple as it seems, is it?
Suspension decided to misbehave again today, and a reset was no help this time.
Removed, cleaned and lubricated the height sensor, including a squirt of switch cleaner on the connector. I also drilled a small hole in the body of the sensor, injected a drop of cleaner, and thoroughly exercised the sensor. Sealed the hole by melting some soft plastic into it, then reassembled.
All seems fine again now, but time will tell...
I suspected that there was a dirty / worn / intermittent spot on the sensor (like a 'crackly' volume control), which initially confused the ECU, and more recently gave the permanent fault. The only thing is that I would have expected it to be OK on intermediate height in that case, as a different spot on the track would then be in use; the fault was more like a poor connection to one end of the pot, perhaps on the connector. We'll see!