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Thanks I will give it a try just hope I can get one I've found it quite expensive to find parts in the UK as it was not a great seller so most parts are main dealer only or breakers
 

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Discussion Starter #23
You have 2 choice:. Take Pot Luck replacing parts you 'think' could be faulty and possibly get nowhere, or take a logical approach by doing some fault finding to get a positive result that something isn't correct. Then fix it or get a new part.

Most of us are born with a working pair of eyes and carefully inspecting suspect parts and wiring first might reveal something if you know what to look for. One member bought the upper lock mechanism and then found a broken pin on the connector. The upper lock is one of the simplest parts in an EOS. 12V drives a solenoid motor for a short 'on' time from a controller to pull back the latch and there's an output voltage on the 3rd wire to tell the system (and display) if the lock is open or closed. Simple stuff for a pair of eyes and a voltmeter. There's plenty in this thread to explain how the upper lock and lower motorised pull down should work, but each part talks through different control modules, even though they might appear to work in sync together.

The EOS has some unique parts not shared by other VAG models and therefore not so common. I'd expect the lower pulldown assembly to be unique, but not the lid top lock?
 

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Eos oil burner on a '58 plate
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Hi Folks, just recently joined the forum.
I have a similar problem with the boot lid lock and am still trying to understand & diagnose it. The symptoms are:
1. The locking bar remains in the lower position after the boot lid is opened via the external (VW) lever. Shutting the lid requires a good slam and, of course, it is not followed by the sound of the motor pulling the lock roller down. And, of course, with out the ability to raise the lock roller, the roof cannot be lowered because the boot lid cannot be released.
2. Disconnecting the boot internal light in the rear trim panel, results, after nearly a minute, the motor operating to raise the lock roller. Thereafter, the boot lid operates normally, I.E. on closing, it latches easily and then is pulled down onto the seals. On opening, via external (VW) handle, key fob or internal switch, the lock roller raises and then the boot lid is released.
3. I have tried to access the wiring diagram for this area of the car but with no luck. I suspect a high resistance earth may be causing the boot light to earth through the lock motor, resulting in it staying in the down position. But without the diagram, I don't know. Next step is to provide an alternative, temporary earth for the light to prove/disprove this.
4. Examination of the boot light unit reveals a resistor across the +ve and -ve. Its resistance seems to be v high, in the Megaohm region to open cct. Don't know if this is correct or what part this resistor plays in the system.

I'll post an update when I have something useful
Andy
 

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The car detects when the pull down motors should run based on the boot light going out - it relies on the voltage difference across the boot light. If there's anything unusual or not right about the resistance across the boot light (e.g. if it's been replaced with an LED) then it will interfere and cause issues. The positive wire for the boot light is a permanent +12V from the central electrics module, and the earth for the boot light is shared with the boot motor after the boot open switch.
 

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Thanks aku-aku. I think your info explains the presence of the resistor - it’s there to maintain the connection in the event of bulb failure. BUT: If earthing the boot via the switch triggers the motor to raise the lock roller, why does mine only work when the boot light is unplugged, permanently interrupting the earth path? Hmmm, need more head scratching (haven’t got much hair left as it is!)
 

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Discussion Starter #27 (Edited)
Unlike the top lid lock/release, the pulldown motor is controlled by the roof control module, even though both appear to operate together as if by the same control signal.

After checking there is +12V and ground on the pulldown motor connector, you can then test the pulldown motor and its controller are good by following Section 4 in my attachment link below. After making a cutout in the ABS rear panel which is now held on by magnets, this is one of my 'Get out of jail' mods for trunk lid lockout to access the motor mechanism.

I used the test circuit shown in Section 4 and initially stuck a pin on the end of a long bean pole, pushed it through the ski hatch then made a momentary contact with the control pins on the pull down motor connector. Later I spliced a couple of long wires to those pins and ran them to just left of the ski panel opening where I can easily get to them if I can't open the lid.

For the pull down to work correctly in BOTH directions, the wiring between its connector (I show the corresponding pins on the roof controller), the roof controller and its connection pins must be good. I suggest you check there is +12V and a good ground on the pulldown motor connector first, then do my test at the roof controller connector. If the pulldown works in both directions, then you have confirmed it and its controller are o.k and start looking for a problem elsewhere?

 

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Thanks aku-aku. I think your info explains the presence of the resistor - it’s there to maintain the connection in the event of bulb failure. BUT: If earthing the boot via the switch triggers the motor to raise the lock roller, why does mine only work when the boot light is unplugged, permanently interrupting the earth path? Hmmm, need more head scratching (haven’t got much hair left as it is!)
When you unplug the boot light, it interrupts the path to +12V (or, at least, increases the resistance to it, if as you say there's a resistor in the back of the lamp holder).

The brown and black wire on the boot lamp goes both to the boot closed switch (which goes to ground presumably when the boot is open) and to the central convenience module (which detects the voltage on that wire).

Is the boot lamp a regular filament bulb, and is it working properly? How does it work with the bulb holder unplugged as compared to just removing the bulb? Do you have another bulb you can test with?
 

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Discussion Starter #29
If earthing the boot via the switch triggers the motor to raise the lock roller, why does mine only work when the boot light is unplugged, permanently
There could be more going on, but here's a possible explanation: The brown/black wire going to the convenience unit should either measure +12 volt or zero volts when the boot lamp is lit. If something works when the lamp (with resistor across the lamp holder) is disconnected that suggests the path to ground is poor and when the lamp is connected you don't get zero volts on the brown/black wire going to the convenience unit. When the lamp is lit and drawing current, the convenience unit may sense boot open with only a volt on that wire when it should be zero or <100mV.

What you have to do is put the correct lamp back, open the lid so it lights and measure the voltage on the brown/black wire going to the convenience unit. If that voltage is more than 100mV lamp lit, you have to then look at where the poor ground is which could be:

1. The brown/Black wires from the lamp going to a termination point in the loom. Follow the wire, unwrap the loom tape to find it. If you are lucky you will see a green corroded V.W brass crimp you can fix and all could be good. This ground termination point has a wire that takes a roundabout route to the trunk switch and a bad connection or corroded wire could be anywhere along that path.
2. This wire goes to a 12 pin connector pin 2 then to an 8 pin connector pin2 and from there to the luggage compartment switch pin 3 on the 3 pin connector.
3. The luggage compartment switch is part of this convoluted path to ground. If it has poor dirty contacts you will get a poor ground. You can put your multimeter ACROSS the lid switch when the lamp is lit to test for <100mV and on the brown/black wire connector pin 1. Measure these voltage with the lamp lit. If it's much more than 100mV you have 2 options: Either the switch contacts have high resistance or the brown wire on pin 2 of the switch is a bad ground. Move your multimeter probe to this wire and check the voltage drop with the lamp lit is <100mV

I think that explains it. There is a ground path of sorts, but when the luggage lamp is lit and drawing current, the ground is poor and there's sufficient voltage drop in the brown/black wires for the convenience unit to regard the voltage as 'trunk lid closed'. That's why you are tearing your hair out and now you are bald!
 
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