Rear spoiler microswitch oddness.

[YPVS]

One little niggle which was annoying me was more often than not, the rear spoiler warning light staying on as I set off driving. The spoiler worked fine from the switch. Pressing and holding the switch on the footwell fuse panel moved the spoiler up or down.

I decided to have a look. The main connector to the engine bay lid was clean, but tried some electrical cleaner anyway, no luck.

I stripped the loom out and it was obvious somebody had been there previously. The 4th brake light on the spoiler was connected with blue plastic bullet connectors for a start and insulation had been replaced with insulating tape. One of the Microswitches was broken too.

I can't find a loom anyway nor can find a part number. This loom does the fan on the engine bay lid, a courtesy light for the engine bay, the motor for the spoiler and 3 microswitches in the spoiler drive box.

The drive box is as below. 2 toothed bars are driven in either direction to pull or push cables to raise or lower the spoiler.

There is a 3 wire microswitch half way down one side of the box, this does thembrake light on the spoiler, so provides an Earth to the light when the top drive bar is to the left (spoiler up) and it's switch depressed.

The other two microswitches are stacked on top of eahc other, near the centre of the drive box. The top one (from when you look at it with the cap off the box, this is actually the bottom one when fitted to the car) does the spoiler down detect. Grey/green and brown wires, which close the circuit when the drive bar is at it's lower end, a cut out along the top end of the bar allows the pin in the switch to extend, making the circuit.

The other grey/brown and brown wire microswitch underneath this as looking at it in the photo, does spoiler up and when the drive bar is extended in up position, a cut out on the lower part of the bar allows the switch plunger to extend, making the circuit. These switches are live when extended, off when the pin is pushed. I opened an old one to confirm this should be the case.

I can't find the correct cable anywhere, even the local OPC can't get the right part number for the loom. The best I could find was a used (but very clean for a used part) cable for a 997. It was identical apart from the connector to connect to the car loom. I bought this and confirmed that all the wires matched my 996 one in colour, and were the same for each component on the loom. I set about joining these wires to the correct colour on the old connector. It wasn't difficult as everything on the loom from colour used for each component etc was the same, it was literally the connector which was different. As I left wire on the old connector and connected the corresponding wires from the new loom to these and have double checked, these must be on the correct pin order.

On fitting and testing, it doesn't work properly. Pressing the manual button to raise the spoiler goes up and keeps on going, grinding the teeth of the bar unless you shut off the ignition. turning back on and using the button to lower the spoiler works as normal. Push and hold to lower, release and it stops. It also stops when reached it's limit. Raising by the button used to only do it if you press and hold and would stop when you took your finger off the button. Now one little press and it carries on forever.

OK, so I thought it must be the upper limit microswitch, but testing at the loom connector with the spoiler up, shows the wires for the upper limit microswitch to be correct. Closed circuit as the pin will be out on the switch. The lower limit switch is also correct. Open circuit, pin in.

When I was testing it with the motor separate from the drive box, after pressing the button to raise the spoiler, it started the motor. As I moved the toothed arm to simulate the spoiler going up, the motor briefly pauses when the upper limit microswitch hits the recess in the bar and allows its pin to extend, causing it to go closed circuit, but then carries on trying to extend the spoiler drive.

I've been at this all weekend now and am flummoxed. The microswitches appear to be delivering the circuit as planned to the correct pins at the loom connector, something clearly happens as it pauses, but then it carries on.

The old loom's sensors seem identical with identical wiring, even the same colour coding. The big difference here is that pressing the raise spoiler side of the button only needs one press now and carries on when you take your finger off the switch. Pressing the other way does not, lowering it is normal and only works as you keep your finger on the button.

Any ideas please folks?

 

[YPVS]

Could it be a sticky relay maybe, as pressing the button to raise the spoiler carries on when you take your finger off the button?

It never did this before and doesn't when pressing to lower it now. You have to press and hold. I need to understand what requires the press and hold action and why this no longer works on the raise side of the button and one touch sets if off with no chance of stopping without ignition off.

It looks like it should be the wiring harness I replaced, but I've checked everything several times now. The microswitches are sending the correct signals to the correct pins on the loom end of the cable, the same pins as the old loom used.

 

[deMort]

Difficult to remote diagnose this so ill just go through my thoughts ..

A relay rarely sticks in the on position , you could swop the relays in the rear board to prove this .

You have checked the wiring on the rear loom but not actually at the control unit to see if there is a connection or if it might be a high resistance connection ...

Connection block im thinking of is o/s and below the drivers seat belt .

The control unit in this case is the instrument cluster .

To me .. spoiler in the up or down position .. try both .. start the car and you get a message .. hence try both to see if you get this message in either up / down or both ..

The instrument cluster needs to see a signal telling it the position on startup, so either of these .. as the message is straight away then its not seeing these signals or it has an internal software fault .

I would clear any fault codes as my first point .. also see what those ( if any ) codes refer to .

With these early cars then from memory we can only clear codes .. we can't see any actual values which does make it problematic to fault find .

I'm not aware of a one touch operation on these , i might be wrong but i don't remember there being one .. as such ..

Im leaning more towards a software issue .

 

[YPVS]

Thanks, some useful info there.

It's my understanding on the 996.1, that the spoiler light comes on from ignition on and should go out as you drive off.

The switch never used to behave like this. It was normally press and hold in either direction to name the spoiler go either up or down.

Down works as normal, but up needs just one brief tough on the up button and it never stops. It also ignores any down press on the button and can only be stopped when you turn the ignition off.

Something is causing it to set the motor off in the up position with the slightest tough on the button and nothing but ignition off will stop it.

That's why I wondered relay. It only works lowering the spoiler for as long as I have my finger on the button, which I believe is normal for the early cars with the button down by the fuse box below the driver's side A pillar. If I remove my finger from a downward press it stood as normal. I need to work out why that stops, but up needs one brief press then carries on regardless, other than the very brief pause as the upper limit Microswitch completes its circuit. It tries to stop it, but something sticks and carries on regardless.

I'll drive it tomorrow and see what happens. There's a chance the switch is broken in the up position.

I'm no expert with wiring diagrams, but this might be a good time to learn.

 

[deMort]

I'm afraid the downside of working on all models is i don't remember the differences between them .. i thought there was no one touch in either direction .. if that's correct then you are left with a jammed relay or the instrument cluster is powering it up when it shouldn't .

Swop the relays .. you have a wiring diagram ? if not pm an email addy please .

Next i would confirm the up position switch is actually being received by the instrument cluster .. kind of left with a software issue of the cluster after that .

It does need a fault code read and clear though .

I have no issue talking you through a wiring diagram .. please be aware though that could easily take up an evening of my time .. happy to help though if i can .

 

[YPVS]

Cheers. I've ordered a second hand relay to try, but on a cabriolet, it'll need to wait until someone can give me a hand taking the hard to off as the other relay board is only accessible with the soft top in service mode.

 

[YPVS]

I manage to get to the rear relay board with the hard top on my Cabriolet. You could just squeeze your hand through the gap between the 2 pop up safety roll bars.

Anyway, I swapped the spoiler extend relay with a second hand unit and still have the same problem.

Whether it's the car getting to 75MPH or the manual switch, as soon as extend spoiler is triggered, nothing will stop it, even when it carried on grinding teeth on the spoiler drive gearbox. The only way to get it to do down again is resetting the ignition and it will do back down as normal on the switch. I.E. ass long as you keep your finger on the down switch it goes down and stops when down.

Up is a different matter. One light touch of the switch and it carries on even when you take your finger off. There is a very brief pause as the motor twitches when it the extended microswitch opens, but it still carries on.

Even though I've double and triple checked the loom from the 997. which appears to have all the same wires and sensors as my old damaged 996 one, apart from the main loom connector which I joined up the same wires to the same pins on, I'll have to assume it's not right somehow as this behaviour start with this loom.

I've seen a second hand entire mechanism for £325 and this seems the best idea now, as the teeth on my drive unit are fairly shot too now.

On a positive note, changing the drivers door latch mechanism has stopped the 2 horn beeps on locking the car. It only beeps on unlocking now, so I've checked the bonnet switch is good and ordered a passenger door latch for £20, which is identical.

 

[YPVS]

Sod it. I've bought a whole silver decklid with everything but the fan for £355 delivered.

Looks in good condition apart from a little scratch on the edge.

Another part in the spares shed. :thumb:

 

[Alex]

I haven't read all the posts, just your 1st sentence. The spoiler light is supposed to stay on until you're in motion, then it turns off. Perfectly normal and documented in your handbook.

 

[Alex]

Just double checked my handbook now I'm home.

 

[Alex]

Could it be a sticky relay maybe, as pressing the button to raise the spoiler carries on when you take your finger off the button?

It never did this before and doesn't when pressing to lower it now. You have to press and hold.

This is perfectly normal too, as stated in the handbook.

 

[YPVS]

I haven't read all the posts, just your 1st sentence. The spoiler light is supposed to stay on until you're in motion, then it turns off. Perfectly normal and documented in your handbook.

Yep, we'll aware of that, but thanks for checking anyway! :lol: :lol:

My problem started with the light not going out when I set off, even if the manual switch worked it in both directions fine.

It's now at a stage where any signal to tell the spoiler to extend, even a very brief press of the up side of the manual switch, sets it off extending and stops at nothing except a very brief pause as the 'your fully extended" Microswitch closes circuit. The only way to get it to respond to coming back down is an ignition off and back on, then use the press to lower side of the manual switch.

I spent hours adapting a 997 wiring harness to fit as my 996 one was clearly damaged and had been butchered before. This even worse behaviour started with the adapted harness, which I wasted a whole weekend checking and checking again that all the same coloured wires went to the same pin at the plug and the same sensor/bulb/fan/motor at the other.

The 996 wiring harnesses don't seem to be available in the type I need with the 4th brake light, so I bit the bullet and bought an entire deck lid in the right colour, from a chap who's done a GT3 spoiler upgrade.

My spoiler drive gears are pretty chewed now anyway, so I need a replacement and again, not available as a separate part.

Tried the up direction relay today as a final straw. No joy.

 

[Alex]

Thought that was your problem as you stated - "the rear spoiler warning light staying on as I set off driving." Sounds to me like your up position microswitch isn't working. Either that or the CU for it is faulty. It's one touch operation to get it up but obviously isn't getting told when to stop.

 

[YPVS]

Sounds to me like your up position microswitch isn't working. Either that or the CU for it is faulty.

When testing with it all apart, the motor twitches as it very briefly stops when the fully extended microswitch is closed. (they close the circuit by allowing the sensor out, when the switch is pressed, they remain open circuit. An indent in the toothed rail, allows it to open and go closed circuit at spoiler full extension). So it clearly is giving a signal of sorts, something then tells it just to carry on regardless though.

It's one touch operation to get it up but obviously isn't getting told when to stop.

I hadn't realised extend was one touch, so your post a couple up clears that one up, Cheers. But the motor twitch as the fully extended microswitch is allowed to open and go closed circuit, tells me it is being told to stop but then carries on regardless. It's not the switch as it stays up when driving too. Nor is it the extend relay as I changed this yesterday.

If I understood how the one touch extend operation is started and stopped, it might help me resolve it. Worth noting that once up, it stops grinding the teeth after a few seconds and stops the motor. At this point, slowing down to a stop or pressing the down button does nothing. You need to reset the ignition to reset it and allow the down button to work.

Can I ask what the CU is? Cheers.

 

[YPVS]

Ah, guessing CU will be the "control unit".

This is the odd bit. The 997 Control Unit is easily searchable, but Google doesn't seem to have heard of a control unit for a 996 rear spoiler.

Am hoping it's not part of the instrument cluster.