Le Mans dash and a faulty suspension pump.

[EDC5]

After a full day at the Le Mans circuit this Friday my C5 developed a fault where the suspension pump wouldn't run. When I got back to the house I was staying at it was clear the car was riding incredibly low.

Panic set in as the thought of having the car recovered back to Britain and the fuss of hire cars was not appealing. A big thanks to Marc who immediately sent me the wiring diagram for the suspension pump. I tested the two fuses for the BHI and the 40 Amp Midi / Strip fuse had blown (in the little fusebox adjacent to the battery).

As a bodge I cut some of my amplifier power cable and used that temporarily to bridge the fuse every time I started the car to lift the suspension. This worked well and thankfully the car is now back in the U.K.

After reading a few threads there appears to be a few causes, the most likely reason being a buildup of carbon brush dust and grease in the back end of the suspension pump motor shorting out the commutator. Apparently some people have replaced the fuse with a 50A fuse however I think this is delaying the inevitable.

I'm going to have to strip down the pump motor which involves removing the BHI from the vehicle. Has anyone got any tips or advice on the process?

[white exec]

Worth checking what sort of current that motor is pulling with one of these...

Sealey clip-on DC ammeter, 30-0-30A and 75-0-75A versions. Available from Amazon, etc.
No need to cut the cable being checked.

Be wary of uprating the fuse, as this could cause a serious issue elsewhere.

[GiveMeABreak]

Glad you've made it back ok Elis, and as we've discussed - finding the cause of the fuse blow is crucial. We suspect the motor could be suffering from the brush crud causing the short and the pump possibly working overtime and overheating.

This chap had the fuse blowing all the time - but when he disassembled the fuse box, the fuse had started to melt onto the contact board - so he cleaned it up and that solved his issue. Worth investigating, although if it's not this, then I can't think of anywhere else to go except the BHI motor itself (I think you have the links for those videos on disassembly still?) and investigation there. A MK II, but similar:



Obviously, whilst driving with the interim solution of a quick fuse bridge to get the pump and height to a reasonable level and then disconnecting will get you out of a fix, the system may not be able to switch the centre spheres in and out or maintain the correct ride height levels as fluid gradually returns to the tank. Without further investigation, I'm not sure at this stage if that particular fuse is solely for the suspension motor and even if not, how the suspension ECU will react to height correction attempts with no motor operation. So it may go into a backup mode and flash the error on screen.

I will see what I can find this morning Elis on the suspension circuit for you.

[GiveMeABreak]

So doing some more digging on the Fuse blown fault, a known issue relates to a leak in the LDS tank from either below the weld area, or from one of the pipes connected to the LDS tank. This fluid can find its way into the pump motor and cause the short - the Citroen solution of course is to replace the LDS tank and the BHI! The more adventurous amongst us would probably opt for a clean up and repair of the motor of course and just replace the tank.

If there is no fluid leak anywhere then replace the fuse.
If that does not work and the fuse keeps blowing, with the electrical circuits checked, then their solution is, you guessed it replace the BHI - as there is likely to be a 'hidden' problem in the BHI.

I'll keep looking....

[EDC5]

Thanks for the advice. Yeah, the 50A replacement doesn't sit happy with me to be honest, although I did read somewhere that the later C5's had a 50A fuse as standard? is this correct?

That little ammeter looks just the job to be honest, I'd go for the 75A version as the inrush to the motor will be very high.

So what I think was happening is that by manually overriding the fuse and running the pump until the suspension reached Med-High before each trip the car would lower to Normal once up to speed. It would't request any more height correction for the rest of the journey so as a bodge it worked OK. But after everyone got out it would lower itself meaning I had to repeat it every time I started the car.

That video in your last post Marc shows the fuses on a MK2, the X7 has them in a separate fuse box near the battery but is otherwise similar.

I'm fairly confident it's not a LDS leak as the level is exactly right.

[GiveMeABreak]

It has been known to pull 80 Amps when faulty so be aware!

Good - no leaks, so the other possibility is an 'internal' leak. I've seen on one of them (I'll try to dig it out) what I think is pointing to a seal that goes in the middle where fluid can get into the brushes... I'll try and find the video and the time point.

[EDC5]

Thanks!

Just to add that I've replaced the 40A fuse and it seems to be working OK. I've raised it and lowered it a few times back to back and it hasn't immediately blown so I'm happy it's not pulling crazy current at the moment.

[GiveMeABreak]

For reference, these are all the ones that I can find that reference the suspension system:

Maxi Fuses
Note - only the V6 models have a 20A (MF7)fuse here for their suspension - not on the 4 cylinder variants) - just included here for reference.

Cabin Fuse G39:

BSI Fuses
Note F13

[GiveMeABreak]

And another strip down: - "Bomba Hydraulica" sounds about right though!

[EDC5]

Hmm, the fuse I changed definitely wasn't a MAXI fuse:



I think only the MK1 and 2 have MAXI fuses.

I changed a strip fuse:

[GiveMeABreak]

This is off an X7 - but you won't have one, the MF7 is only for the V6 (see my note above the table) I just put these up for future reference to cover all the X7 models.

These are them on an X7:

[white exec]

Some of those blade fuse ratings are just crazy: 80A and 100A, for example - capable of welding!!
Fair old PSA history of high-current fuses having inadequately rated fuse holders/receptacles on the fuse boards.

F2 (in the engine bay) the best known trouble-spot on XM, the OE 30A fuse looking after A/C and blower. Over time, the hot blade contacts oxidise, then fail to make decent contact, then overheat further and eventually melt both fuse and fuse-board. Citroen's answer was to uprate the fuse to 40A, which of course completely failed to sort the problem.

I find it worrying to see such high-rated fuses doing routine jobs, and often indifferently supported by way of wiring and connectors. High wattages and a 12v supply make poor bedfellows, and Citroen's move towards electrically powered (rather than engine powered) pumps doesn't help. Squeezes a whisker more mpg, of course, but what a way of doing it!

[GiveMeABreak]

Yes it's the BSI Chris on these modern cars - the computer brain that handles just about all the electrical stuff on the car, plus all the change from mechanical to electro pumps for the power steering pump, suspension pump / BHI, Stop Start and regenerative braking, blah blah - so it's amazing that things last as long as they do!

I'm a bit paranoid though - if I see anything powdery or something that isn't right, I'm in there armed with sandpaper, grease & contact cleaner to get it all cleaned up - but not had anything to worry about so far with the X7 on the electrical front touch wood.

[GiveMeABreak]

But if you look at the first video I linked to: viewtopic.php?f=3&t=60408&p=579205#p579193
you'll just about see that the fuse on the MK II C5 had melted about that blade.

We've all seen what can happen though on these under bonnet fires.....

[EDC5]

High wattages and a 12v supply make poor bedfellows, and Citroen's move towards electrically powered (rather than engine powered) pumps doesn't help. Squeezes a whisker more mpg, of course, but what a way of doing it!

I fully agree, I'm not keen on the idea of electro-hydraulic pump on a car when there is a very large and obvious source of rotational energy in the immediate vicinity of the engine bay. What's even crazier is that the X7 has two electro-hydraulic pumps, one for steering and the other for the suspension.... hoe can that be better than one engine driven one?

I've had the car doing several rounds of citroebics and the new 40A fuse hasn't popped yet so could it be a case of fuse fatigue or is that just wishful thinking?