C5 Estate Tailgate - no unlock

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pandalooma
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C5 Estate Tailgate - no unlock

Post by pandalooma »

The finger switch under the number plate trim does not open the tailgate release.

The upper window release does work correctly

Using the Xsara wiring diagram posted here (I know it isn't the right one but it matches the connectors and layout on mine) I note that:

The finger switch is faulty - it does not short to ground when actuated... you'd think that would be it, a single fault, but no. Temporary replaced that switch on a flying lead makes no difference.
The connector on the actuator tells me: there is never any 12v pulse arriving on the connector. The "I am closed" microswitch inside the actuator is flipping correctly when the latch is open/closed.

It would be really odd to find that there's a fault between these two and the BSI, like broken lead or connector, but I'm thinking I should check continuity of these two wires - the finger switch input to the BSI and the pulse output from the BSI. Where is the BSI? Are there any fuses or other components associated with this function I could check?

Thanks...again!
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GiveMeABreak
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Re: C5 Estate Tailgate - no unlock

Post by GiveMeABreak »

The usual issues with these is either the switch that needs replacing, or the area where the rear loom enters the tailgate. The wires inside the protection tube can wear over time with opening / closing action and break / short.
pandalooma
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Re: C5 Estate Tailgate - no unlock

Post by pandalooma »

Yes the switch seems to be bad so I have stuck a temporary push-button switch across it which does now do what it is supposed to. But still not working. How can I check continuity back to the BSI?
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GiveMeABreak
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Re: C5 Estate Tailgate - no unlock

Post by GiveMeABreak »

Not understanding that last bit - you say you've put a temp switch on and it's working, but then say it's still not working?

If you're quick you can pick up a genuine OEM contact switch here for £8 inc. shipping! They are about £44 from Citroen.

https://www.ebay.co.uk/p/649801114
pandalooma
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Re: C5 Estate Tailgate - no unlock

Post by pandalooma »

Sorry Marc, what I meant was - the temporary switch is working fine BUT it is not making the BSI release the catch
wheeler
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Re: C5 Estate Tailgate - no unlock

Post by wheeler »

Duplicate post
Last edited by wheeler on 25 Nov 2021, 13:31, edited 1 time in total.
wheeler
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Re: C5 Estate Tailgate - no unlock

Post by wheeler »

GiveMeABreak wrote:
24 Nov 2021, 16:19
The usual issues with these is either the switch that needs replacing, or the area where the rear loom enters the tailgate. The wires inside the protection tube can wear over time with opening / closing action and break / short.
Have you checked this👆🏻?
I wouldn’t even start to think about doing wiring checks up to the BSI yet till you have checked in here. Its the most likely issue.
Is this a mk1, 2 or 3?
Do you have diagbox?
pandalooma
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Re: C5 Estate Tailgate - no unlock

Post by pandalooma »

Thanks wheeler - The switch itself is out of the picture now because I have replaced it with a good one. The loom has a cover on it for most of the visible part but from what I can see no wires are broken. It's an '06 mk2 and I don't have a diagbox.

If I knew where the BSI was and the pinout or cable bundle was accessible I would:

1. At the BSI output pin - the one which drives the solenoid - I would check to see if it ever went +12, when the button is pressed. If it did I would know that the wire between that pin and the latch unit is open.

2. If that output pin was not going +12v when the button is pressed I would want to see that the "I am closed" wire from the latch unit is truly taking the corresponding BSI pin low, to ground, when the latch is closed. Because it looks like the BSI will not send a "close" pulse to the latch unit if it is already closed.

3. If that pin IS toggling when the latch is open/closed I would check to see if the "open" instruction from the button is getting to the BSI. I think it is active-low, ie goes to ground when pressed.

Am I right in thinking that as far as the tailgate latch is concerned there are only three connections back to the BSI - "I am closed" "Please open" and +12v pulse to actuate the solenoid?
wheeler
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Re: C5 Estate Tailgate - no unlock

Post by wheeler »

If I remember right without looking at a diagram only 2 of the wires connect to the BSI. The 12v output pulse and the earth switched signal from the open close switch, the other connection is a permanent earth.
pandalooma
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Re: C5 Estate Tailgate - no unlock

Post by pandalooma »

"The 12v output pulse and the earth switched signal from the open close switch, the other connection is a permanent earth."

I just dismantled this to find:

That's right but there is a third, from the actuator back to the BSI. It is there to tell the BSI that the lock claw has reached its 'open' position, there's a microswitch inside the unit which detects this. Because the mechanism is operated by a motor rather than a solenoid it can't work on a pulse. Without this information the BSI wouldn't know when to stop powering the motor (cue tearing of nylon gears...)

Is it possible that anyone here could fix me up with a schematic for this?
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GiveMeABreak
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Re: C5 Estate Tailgate - no unlock

Post by GiveMeABreak »

There's not much more to show, but here you are:

6260: Boot or tailgate lock motor
6237: Boot unlocking switch

Image
wheeler
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Re: C5 Estate Tailgate - no unlock

Post by wheeler »

As confirmed by the diagram there are 3 wires on the tailgate latch & only 2 of them go to the BSI. I doubt there is any feedback to the BSI from the lock motor, they are normally just a fixed timed pulse, probably 0.5 seconds.
If you give pin 2 of the 40 way grey on the BSI a breif 12v feed with the plug disconnected the it should pop the lock open (assuming the permeated earth is at pin 2 of the latch). If not the wire is wire is broken.