C5 - Suspension not working - relay fault?

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Johnno
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C5 - Suspension not working - relay fault?

Post by Johnno »

Hi. Yesterday my 2004 C5 was working fine - now, there is no activity from the pumps and the internal switch has no effect, up or down. I've checked both fuses referred to in the manual as being connected to the suspension. Both ok. I'm assuming it is an electrical failure, possibly a relay. The car is now sitting on the driveway getting lower all the time. The LDS reservoir is fine.

Does anyone have any experience of this? (Bizarrely, yesterday a young lad asked for my advice on this very problem!! He'd been given a 'Y' reg C5 which would not rise from the low setting, irrespective of the switch position - now mine has caught the same disease).

I hope someone can help.

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myglaren
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Post by myglaren »

Can you test for a voltage being applied to the pump? If there is one I would suspect a pump failure, otherwise the suspension ECU, for which a Lexia session would help pinpoint any faults arising.

Johnno
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Post by Johnno »

Thanks, Steve - checking for voltage would be a good start. Do you know where the pump is located? It also occurs to me that the ECU may be on strike, so I'll disconnect the battery tomorrow morning and see if it resets.

Could this be a height corrector issue? If these are electronic, it could be that the ECU needs to see a signal from both before telling the pump what to do.

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myglaren
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Post by myglaren »

It is on the left of the engine bay below the LDS reservoir. I'll send a photo in the morning, bit dark here now.
Could this be a height corrector issue? If these are electronic, it could be that the ECU needs to see a signal from both before telling the pump what to do.
It is not unthinkable but rather unlikely that both have failed at once.
I believe that viorelovidiu had a similar problem but just with the rear sensor failing.

Edit to add:
Image

You can just see the pump under the reservoir in this photo, to the left of the power steering pump pulley, above the alternator.
Click the image a few times to get maximum size and resolution.
Last edited by myglaren on 03 Apr 2010, 20:20, edited 1 time in total.

cachaciero
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Post by cachaciero »

If the pump is not running it's not getting elecky or it's broke.

Have you checked the MAXI fuses on the engine relay unit in the engine compartment?

Apropos suspension ECU that is in the pump.

cachaciero

Johnno
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Post by Johnno »

Thanks, guys. I guess that's my Sunday sorted, then. If the pump is dead, I shall be most vexed - a pump and ECU sold on ebay a month ago for £26! The young chap I referred to in my first post said that the garage that gave him the car (a trade-in) had told the owner that "it'd be £1000 to replace the pump". I think they just wanted to sell him another car...

Johnno
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Post by Johnno »

A temporary fix has been effected. There was no voltage on the pump primary feed, but there was excitation voltage. I bridged directly from the battery, started up and the car rose to the correct height, with the manual raise/lower working fine. Everything else works, so it would seem that the main power to the pump has been interrupted somewhere. Back to thinking about relays again.

Thanks for your input.

cachaciero
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Post by cachaciero »

I repeat have you checked the 30 amp maxi fuse in the engine relay unit under the bonnet? This is the principal feed direct to the pump.

cachaciero

KevMayer
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Post by KevMayer »

I've had a look at my french manual for the C5.

The supply to the suspension motor comes directly from fuse MF8 which is 40 amp (hence the reference to MF I suppose... :lol: ). This fuse lives with 7 other large fuses beneath the engine compartment fuse module. This is next to the ECU housing.

Please note, there are 8 very large fuses beneath the engine compartment fuse module. You will only be able to see them if you remove the fuse module from its position. Lift it right up and MF8 is underneath. There is a small fuse 8 on the top. This is not the one you need to check.

The supply comes from the battery to fuse MF8 and then to the pump motor. If the supply is missing then the most likely thing is that this fuse has blown. Otherwise there could be an open circuit. I'd check the fuse first.

Edit Cachaciero just beat me to it.. :roll:

Johnno
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Post by Johnno »

Kev/Cachaciero

Ta for the info. I checked the fuses yesterday and could find none that were blown. Mind you, Kev's note about fuses under the under-bonnet fuse box is a bit of a revelation. I was working from the Owner's Handbook which lists the fuses with each fuse's function - it doesn't mention any 40 amp jobbies to do with suspension! In fact, there is only one 40 amp fuse listed and that is for the air blower.

I'll dig around tomorrow. Of course, a blown fuse always prompts the question - why?

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Paul-R
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Post by Paul-R »

The reason the handbook doesn't mention these fuses is that they are supposed to be a dealer-only replaeable item.