Computamedic

Adrian,

On looking through the archives in relation to my permenet aralrm problem (remember, 89 C4 with the basic alarm), I came across a reply you made last year on the subject of turning off an activated alarm (to lock and unlock the offending door).

At the end of that reply you made a comment about "check the glove box switch". The reason that comment caught my eye is that I've noticed that my glove box switch doesn't turn off the glove box light. I know the light swivels into 3 positions - but I've got (1) permanently off, (2) permanently on and (3) permanently on!! The switch never affects the state of the light.

I also appear to have a similar phenomenon with the engine cover light. I've even disconnected the wire that goes to the switch - and the light stays on!!!

I'm guessing that the aftermarket alarm is wired into this circuit somewhere and, if this is the case, I realise I can't expect you to comment. It just raised a hope that there might be some connection (pun).

Regards

Dave

John Boggiano

Dave,

Re the engine lid light - you might find that it's on whenever the boot light is on and vice versa. Strange, but true.

Computamedic

John,

Thanks for the tip. It's difficult to follow the designers logic there isn't it?? It would certianly explain what I've seen so far - I'll have to do a more scientific test to convince myself but you may just have hit the nail on the head.

Thanks again


Dave

raymond-turner

This is the same on mine, all lights are on together, engine, boot and interior, must be a logical reason, but it escapes me.

DaveK

It seems to be true of UK cars. Those people who drive on the wrong side of the road seem to have independent lights.

Computamedic

Hi all,

Just to confirm everybody's thoughts, a quick test revealed that you are absolutely right. Luggage compartment, engine cover and glovebox lights all come on at the same time. Not limited to RHD cars since my LHD German original works that way too.

For the life of me I cannot imagine why the design engineer would choose to make the wiring so complicated for absolutely no discernable advantage!!

My only light-related problem now seems to be that the glove box light cannot be switched on or off via the button switch operated by the glovebox lid itself, regardless of the tilt position of the light unit. Maybe a duff switch. Further investigations to be made.

Still gotta sort out this damn alarm problem tho.

Regards


Dave

Adrian

Dear Dave,
Sorry I have only just got back from Geneva and the motor show and I had to update my web site and do other things first.
The glove box switch is a known problem with the alarm system. If it is not set right and noce and tight it will set off the alarm. You will have to forgive me but I cannot remember the exact problem you have with your alarm but this switch will have an impact on any alarm system fitted. I would recommend you get it fixed.
On why do all the lights come on. I have no idea. It has always seemed pretty silly to me but I do remember this also happened on my old 944 from 1985 so it is not something new.
Ciao,
Adrian
964C4

Computamedic

Hi Guys,

I wonder if some kind soul could enlighten me as to how the glove box light is supposed to work. My only manual is in German and my schoolday German is not up to the task!!

I realise that there is an earth contact switch operated by the glovebox lid and I realise that the light unit is tiltable to any of 3 positions, which I assume to be off, switched and on. On and Off operate as expected but I cannot get the light to operate in the third position. I'd like to know if it's necessary to (a) have the ignition on, (b) have the lights on or (c) do anything else??

My root problem at the moment is that my factory alarm is permanently armed so activates (i.e. horn sounds) when either door, luggage compartment or engine compartment are opened. Although there is apparently a connection between the glovebox switch and the alarm, the alarm DOES NOT activate when the glovebox is opened. Should it??

The problem appeared overnight after a day of approx 250 miles driving in, latterly, wet conditions. All was well when the car went in to the garage - in the morning the alarm sounded. I haven't been able to start the car for nearly 2 weeks now - and I'm getting withdrawal symptoms!!

Regards


Dave

Julian Thompson

Guys - don't panic.

I'm a car alarm installer and the reason all your lights come on together is simple.

Most alarms (including stuff made for OEM people like Porsche) only have negative switch trigger inputs for doors and boot.

So you wire the doors to the door switch input, the boot to the boot switch input and.... ah - what to do with the glovebox (in this case) and the bonnet?

Well, what you SHOULD really do is to diode off these three circuits so that when you open, say the boot, no lights come on elsewhere but many times all three circuits will be connected together anyway - it won't cause any damage but it is "messy"and very interesting that Porsche didn't bother to diode it (if indeed your alarms are actual factory fit rather than dealer fit - when I would believe anything!!!!!)

Julian Thompson

So to answer Computamedic's question - you should just try disconnecting the plug to the glovebox for a test - this will prevent the alarm from seeing a negative of any description on that circuit and will eliminate the glovebox switch from your enquiries. If the alarm still plays up it is something else.

Adrian

This test may only work if power is removed from the alarm first. For an early model 964 this is very hard to do. The problem with disconnecting things is that it may keep the alarm disabled. Remember when you do this disconnecting the alarm is already off because you will have the doors unlocked and one door open etc etc. It may not arm itself again.
Ciao,
Adrian
964C4

Julian Thompson

Err, not really - you are only disconnecting switched inputs that cause a trigger when they are pulled to ground - if you disconnect the alarm you can't do the test!!!

Jue

Adrian

You disconnect the alarm, then you disconnect the switch and then you reconnect the alarm and then do the test.
I can tell you from experience that when my luggage compartment switch went open (switch broke apart and fell out) the whole alarm system stopped working. The alarm saw the luggage compartment open all the time and did not arm itself. However just disconnecting the connector in the luggagement compartment under the hinge does not impede the alarm operation yet technically it is same thing.
I am saying your test idea is unreliable. It might work on the hand it might not. There is nobody who knows how the early alarm systems work internally nor how to reliably test them. A tester can be used on the later 1991 model year and up versions. Add to that aftermarket installations and you have a whole different ball game. Most people cannot even tell you how they are wired in.
Ciao,
Adrian
964C4

PS: These are all factory alarms I am talking about. The dealer installed or shop installed aftermarket systems are additions and a mystery in their own right. Most have a rats nest of wiring behind the dash.

Julian Thompson

OK Adrian I see what you're driving at; perhaps we have crossed wires (quite a good joke as well, eh, given the topic!)!

It is an interesting point about the unit not "seeing" the glovebox - if you think about it the switch will always be "open" circuit when the glovebox is shut and "closed circuit" when the glovebox is open - so maybe the alarm unit "looks" for another circuit to be complete through the glovebox light or something? Most irregular!

Perhaps the best thing to do might be to remove the glovebox and actually work to get the switch operating properly so you can be sure it isn't the glovebox causing your problem!

Anyhow, just to clear up the aftermarket alarm issue - if it is an aftermarket alarm there will be only one wire tacked to the switch loom which will be hunting out a state switch when the glovebox is opened - and you can safely remove this wire and do your test with no probs.

Computamedic

Hi all,

Just to add some clarification here (on my problem, at least), my tests have revealed that the glove box switch itself seems OK (tested outside the car with a meter), the light also tests OK but when connected the light will not work in ANY position via the switch - it will only come on when swivelled to the "ON" position - and then it will come on under any conditions regardless of luggage/engine cover state or glovebox switch.

Just to clarify the alarm situation, it seems that my factory alarm/immobiliser is permanently armed - even after activating and reseting (via the door lock). Also, the doors will not lock (other than via the turn **** inside the car) - the key will not lock either door, although it will unlock both doors (electrically) if they were previously manually locked. On occasions, when re-connecting the battery the central locking has spontaneously locked both doors(!). That, at least, proves the door lock mechanisms are working.

There IS an aftermarket alarm too - an Autowatch - and my suspicions are focussing on that at the moment.

BTW disconnecting the power feed to the luggage/engine light circuit does not help - the alarm still activates when a door is opened although, obviously, not when the luggage/engine covers are opened. At no point does the glovebox have any affect on the alarm.

Best regards


Confused of Milton Keynes