How to Replace Roof Sensors

Azteccamper · Jun 15, 2021

Update on roof repair (fault code 1000):
I bought 4 x sensors to replace them following @Lambeth Cali instructions, but I just couldn’t get the roof to open to allow me to do the fix. So I booked into my local VW dealer to see what they would say.
I asked them their process and in fairness told me that fault code 1000 was going to be sensor related. Which I pretty much knew thanks to this forum.
On confirming this during their investigation I then had a choice:
1. Have to buy the full roof harness (£270+vat) and have it fitted + 15 hrs labour (£95 + VAT per hour)
2. They would snip the sensors off the harness and splice them into the old harness + 3 hrs labour.
No brainier price wise - but they refused to use any of the 4 x sensors I had purchased. It only required 2. Or tell me how they got the roof up - not that I fancied fiddling with the motor, etc..
In total it cost me £710. Roof works perfectly.
So if anybody wants to buy a harness with 2 sensors and another 2 separate sensors let me know!

Main thing is we can get out this weekend without walking with a hunch after it.

Lambeth Cali · Jun 15, 2021

Getting it working is always the most important thing. And of course swerving the £2000 option 1. I wonder if they would have offered option 2 if you hadn’t looked like you had an idea what the fault was.

steve_b · Jun 15, 2021

Azteccamper said:
Update on roof repair (fault code 1000):
I bought 4 x sensors to replace them following @Lambeth Cali instructions, but I just couldn’t get the roof to open to allow me to do the fix. So I booked into my local VW dealer to see what they would say.
I asked them their process and in fairness told me that fault code 1000 was going to be sensor related. Which I pretty much knew thanks to this forum.
On confirming this during their investigation I then had a choice:
1. Have to buy the full roof harness (£270+vat) and have it fitted + 15 hrs labour (£95 + VAT per hour)
2. They would snip the sensors off the harness and splice them into the old harness + 3 hrs labour.
No brainier price wise - but they refused to use any of the 4 x sensors I had purchased. It only required 2. Or tell me how they got the roof up - not that I fancied fiddling with the motor, etc..
In total it cost me £710. Roof works perfectly.
So if anybody wants to buy a harness with 2 sensors and another 2 separate sensors let me know!

Main thing is we can get out this weekend without walking with a hunch after it.

Glad it's fixed. A set of pictures of the harness and even better if you can work out what wires go where might aid others in future.

Azteccamper · Jun 16, 2021

Full harness.
Connectors to attach to Roof hydraulics control unit J768.
Sensors taken from here (two sensors I purchased pictured as well).
Other side of van roof sensors attached to harness.
Details of layout in brochure.

Lambeth Cali · Jun 16, 2021

Azteccamper said:
Full harness.
Connectors to attach to Roof hydraulics control unit J768.
Sensors taken from here (two sensors I purchased pictured as well).
Other side of van roof sensors attached to harness.
Details of layout in brochure.

View attachment 80136

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So which sensors were replaced? 2 on which side of van? How did they know they were the faulty ones? I wonder if they had a diagnostic test.

Azteccamper · Jun 16, 2021

Lambeth Cali said:
So which sensors were replaced? 2 on which side of van? How did they know they were the faulty ones? I wonder if they had a diagnostic test.

Both front ones. They said they could test to see which ones were faulty - I wasn’t convinced.
But it’s done.

Azteccamper · Jun 16, 2021

Azteccamper said:
Both front ones. They said they could test to see which ones were faulty - I wasn’t convinced.
But it’s done.

And I’ve got 6 spare sensors and a loom

steve_b · Jun 16, 2021

I must admin I am surprised how many connectors there are on the loom. Be good to take it apart (figuratively) and work out what is connected where.

4 sensors looks like 3 wires each side (1 power plus 2 signal returns) - so theoretically a 6 pin connection at a plug end.

Pump motor connection is a single 12v feed where polarity is reversed to reverse direction , not sure what the rest of it is for. Shame we can't see what plugs into what .

I need to lift my roof up and properly examine this - shame the VW diagnosis doesn't give you a code for sensor readings - that would be immensely useful. I would expect each one to return a 1 or 0 (or failure) so the unit should know that something like

front 2 sensors = 1 and back 2 = 0 means roof up
front 2 sensors = 0 and back 2 = 1 means roof down (might have these the wrong way round)
anything else, particularly front and back =1 means error

If you could read the values and then understand them you should be able to pinpoint the faulty unit.
Or it could be as simple as if the roof refuses to raise it is always the front sensors...

Loz · Jun 16, 2021

vbk1975 · Jun 17, 2021

steve_b said:
I must admin I am surprised how many connectors there are on the loom. Be good to take it apart (figuratively) and work out what is connected where.

4 sensors looks like 3 wires each side (1 power plus 2 signal returns) - so theoretically a 6 pin connection at a plug end.

Pump motor connection is a single 12v feed where polarity is reversed to reverse direction , not sure what the rest of it is for. Shame we can't see what plugs into what .

I need to lift my roof up and properly examine this - shame the VW diagnosis doesn't give you a code for sensor readings - that would be immensely useful. I would expect each one to return a 1 or 0 (or failure) so the unit should know that something like

front 2 sensors = 1 and back 2 = 0 means roof up
front 2 sensors = 0 and back 2 = 1 means roof down (might have these the wrong way round)
anything else, particularly front and back =1 means error

If you could read the values and then understand them you should be able to pinpoint the faulty unit.
Or it could be as simple as if the roof refuses to raise it is always the front sensors...

The issue with the Cali roof ECU is that it added on as part of the conversion. All the standard T5/T6 ecus you can read part numbers, fault codes, channels etc as they are connected to the vehicle network, the roof isn’t. So all the faults you can get out of the roof ECU are via the roof control module and are a lot more high level and not specific. From my digging around the roof ECU is actually the same hardware as SAAB & OPEL convertibles and from what I can determine on those cars it is connected to the their vehicle networks and you can do a lot more diagnostics, ie determine exactly the sensor that is faulty and in theory drive the pump via diagnostics routines and bypass the sensors. I have had a little play with this but trying to get hold of aftermarket GM diagnostics software isn’t easy (well free) and whilst the hardware appears to be the same, the software is different due to the roof operation. I was hoping that there might be a way to use GM diagnostics on the controller and save Cali owners a lot of time and money, but we will see.

The way two wire hall sensors work is they have two different states which means they pass different currents through them rather then being like a traditional switch so they are incredibly difficult to diagnose without the ECU, in theory you could use a current clamp or put a good multimeter in the sensor circuit, but the values are very small and vary with voltage, so it is one of those yes in theory but ….

steve_b · Jun 17, 2021

I have a couple of hall sensors here that @Lambeth Cali sent me - I am to try and work out what is "normal" , current wise. Of course I don't know which one , or both is faulty

but should be able to get an idea. I can rig a circuit up or hook it to an arduino and a crude scope. when I get time, which is my problem!

vbk1975 · Jun 17, 2021

steve_b said:
I have a couple of hall sensors here that @Lambeth Cali sent me - I am to try and work out what is "normal" , current wise. Of course I don't know which one , or both is faulty but should be able to get an idea. I can rig a circuit up or hook it to an arduino and a crude scope. when I get time, which is my problem!

Go with LOW being ~15mA at 12v and HIGH being ~3mA at 12V as a going in point. However the roof ECU will have some sort of Hall effect output circuit that will control the current, so I would go with using that as a starting point, I bought a roof ECU from eBay for ~£20

edited: just another thought, given the issue is probably with the sensor magnets no longer being magnetic as they have rusted. Perhaps placing a powerful magnet on top of the sensors could be used as a quick check, ie you might be able to see the roof status change

steve_b · Jun 17, 2021

vbk1975 said:
edited: just another thought, given the issue is probably with the sensor magnets no longer being magnetic as they have rusted. Perhaps placing a powerful magnet on top of the sensors could be used as a quick check, ie you might be able to see the roof status change

I had the same wonder in a different thread but using a block of iron like a hammer head - be interesting to see the "normal" behaviour and whether it can be influenced with magnets or a lump of metal, it might be enough to trick the sensors into thinking situation normal to at least allow the roof to be opened. Just need to understand what "normal" is

Lambeth Cali · Jun 18, 2021

vbk1975 said:
Go with LOW being ~15mA at 12v and HIGH being ~3mA at 12V as a going in point. However the roof ECU will have some sort of Hall effect output circuit that will control the current, so I would go with using that as a starting point, I bought a roof ECU from eBay for ~£20

edited: just another thought, given the issue is probably with the sensor magnets no longer being magnetic as they have rusted. Perhaps placing a powerful magnet on top of the sensors could be used as a quick check, ie you might be able to see the roof status change

They were all still quite magnetic. Even the completely rusted one could be placed on a radiator and would stick.

Lambeth Cali · Jun 18, 2021

Just another note. The sensors had numbers on which implied they had to be placed in a specific order. I suppose that also could have been due to length of different bits of the loom.