C5 height sensors

[Gibbo2286]

Have you had a trawl through this thread James?

I have a vague recollection that the single wire is to activate the pump.

That's correct, I think it's called an exciter wire by the leccies.

My suggestion for testing does work HR used it a few times when working on the C5s, I don't have one now so can't show you with pictures.

[Hell Razor5543]

I don't know what I am doing wrong, but the pump is not running. The 40A fuse has not blown, I have done a BSi reset, and still nothing. I have a second pump unit (I swapped the pump controller over), and still nothing. I have cleaned up the original pump and refitted it, but the suspension isn't lifting her.

[Gibbo2286]

Does your old pump work now you've cleaned it up?

[Hell Razor5543]

Neither pump is turning, and I know my limits where electrics are concerned. The original pump has an acrid smell which I hope is not the windings. I am also considering the possibility that the wiring (from the maxi fuse to the motor) may have been damaged, as there was a 60A fuse where a 40A should have been used.

What voltage should there be on the exciter line?

[Hell Razor5543]

I may be getting somewhere. Is there a direct feed from the maxi fuse box to the pump? I disconnected the battery, and it is open circuit from the 40A fuse to the live wire on the pump connector (and virtually no resistance between the earth wire and the chassis).

[GiveMeABreak]

The supply first goes from the Maxi Fuse 8 to the relay (1704) as located below where I have highlighted in yellow.

The supply is on Pin 3 of the 5 pin connector.
The Earth is on Pin 2
The connection to the BSI (Fuse F13) is on Pin 1
The supply to the rear Height Corrector is on Pin 5.

[Hell Razor5543]

Thanks again, Marc. Do you know how to access the relay?

[GiveMeABreak]

If it's not visible where shown in the inner right wing, then it may be hidden or covered under the wheel arch lining. I never had an issue with it on my MK 2, so can't advise where it actually is, but it is in the vicinity as on the diagram.

[Hell Razor5543]

Thanks again, anyway.

[Hell Razor5543]

I may have progress. The relay has NOT failed, as there is 14V at the pump connector when the engine is running. I don't know it it is correct, but there is 0.75V on the exciter line. If that is correct it would suggest the power transistor in both motors has failed.

For anybody who needs to know, the relay appears to be inside the engine back close to the suspension mount (which might make it tricky to remove). It is a large brown unit.

[Hell Razor5543]

OK, I have made some more progress (of a sort). With the original motor in place (cleaned up, but with an acrid smell) I ran a few Lexia tests. She did not lift, but when I checked I found that the fuse had blown. This suggests that she TRIED to lift, which is a step forward. I have to hope that the motor for the other pump isn't wired differently (there are a few differences, but it is from a slightly newer car, so this may explain them). I have striped and cleaned it (there were signs of carbon sludge), so I will see what tomorrow brings. The control block (on top of the pump) will be swapped between the units.

[Hell Razor5543]

I can confirm that (certainly between model siblings (VTX+ saloon/estate)) the hydraulic pump/motor (but not necessarily the valve control electronics) are compatible. Like the mad scientist says, just after his creation has been zapped by a lightning bolt, "It's ALIVE!".