1st Boxster, 1st Problem

[StuartWaite]

Hi Guys
I have just bought my wife a Boxster 2.7 for X-Mas to replace her beloved MGF :thumbup:
The first day home the alarm went off and we found that the battery was completely flat. 1st problem was how to release the front lid - a quick google search pointed to supplying +12v to fuse C3 which we duly did, opened the lid and replaced the battery with a new Silver 85Ah 850CCA model. All was OK for another two days until the same thing happened :cursing:
Monitoring the static drain on the battery shows a very strange pattern. Normal background drain is about 50mA but this spikes to 6A, 8A or even 10A for about ten seconds every minute then it drops back down to the normal 50mA
Systematically removing the fuses whilst monitoring the battery drain led us to fuse E3 (30A) which would appear to be related to the Power Seat Memory which is doubly odd as the car only has manual seats!
I have a workshop manual on order to help me with further diagnosis but until this arrives does any of you tech savvy guys have any idea what could be occurring ?

The floors, doors  and under seat area is bone dry
Cheers
Stuart
Ludlow UK

Edited January 6, 2016 by StuartWaite

[wizard]

Is it all factory-built spec or could a previous owner have installed something wired to E3 ?

[Hilux2400]

If the car has only manual seats what does fuse E3 drive?

 

Have you tried removing the fuse and finding out if everything else functions and is there still a call on the battery when it is removed? 

 

Does it have heated seats and is the switch faulty?

Edited January 6, 2016 by Hilux2400

[StuartWaite]

Hi Guys

Thanks for your replies

The car is in lovely original condition - as far as I can tell!

It has manual full grey leather seats without the heating option.

Fuses E3 & E4 are both 30A and should be for seat positioning/memory

As a temporary fix I have removed E3 and the dark current has dissapeared and everything seams to be working fine

I'm not happy to leave it like this until I have found the actual cause so any further help would be appreciated

Regards

Stuart

[Hilux2400]

I assume the seat memory works from instructions from the management system which would throw a relay to activate the seat motors.  It could be that the management system is drawing current and is activating a relay.  When is discovers that there is no message return, it goes back to non-activity mode and it continues to cycle. 

 

My seat motors (non memory) will work when the ignition is off. 

 

Just a thought, as I don't know the answer. 

[wizard]

Odd.

I have a 2003 2.7 without electric seat adjustment. I've just been out to look and I also have E3 & E4 30 amp fuses.

Like Hilux2400, I don't have an answer but assume the cabling for electrically operated seats is part of the loom installed on all 986s.

E3 is for the driver's seat, I believe, and it may be an idea to have a close look under that seat to see if the connectors on the end of the cables are fixed in the same manner as those under the passenger seat.

[Hilux2400]

Odd.

I have a 2003 2.7 without electric seat adjustment. I've just been out to look and I also have E3 & E4 30 amp fuses.

Like Hilux2400, I don't have an answer but assume the cabling for electrically operated seats is part of the loom installed on all 986s.

E3 is for the driver's seat, I believe, and it may be an idea to have a close look under that seat to see if the connectors on the end of the cables are fixed in the same manner as those under the passenger seat.

On my 996 there is a multi wire loom going to a location under the seat where there is a connector block. The input has more wires than the output, as I have only one motorised control for the back tilt mechanism. To get to this connector you really need to undo the set screws that hold the seat in place and then tilt the seat back.  However, I understand that separating this under-seat connector can activate the air bag system.  I have done this, but only after leaving the ignition off with the key out for about 20 minutes.      

[StuartWaite]

Bingo

 

Thanks Wizard

I assumed that as I didn't have fore/aft positioning or memory buttons my seats were pure manual - WRONG
You pointed me in the right direction and I now know that even manual seats have power backrest controls supplied by E3 for the left seat and E4 for the right. Further inspection showed that the left seat back switch was stuck on thus trying to drive the backrest to the fully to the rear and was responsible for the strange cyclic current drain. I guess the motor control circuit was obeying the command from the switch and trying to move the seat, failing as it was already full travel, aborting, then re-trying on the next timeslot. As both these fuses are hot even with the ignition off the battery didn't stand a chance!
In my defence I found fuse E4 was actually blown and so the control on the right (drivers) seat was not working reinforcing my assumption that the seats were manual only!
I have replaced both fuses E3+E4 and played about with the switch and it seems to be working fine now. Quite a simple fix in the end and no nasty air-bag incidents :-)

Thank you for taking the time to read my posts and for reading between the lines and intelligently coming up with the right answer - well done

Well done to also to Chris H1 and Daz85Lux of the TIPEC forum who were both correct and helpful.

Cheers
Stuart

[wizard]

Good for you, Stuart .... and I've learnt something in the process !

[Hilux2400]

Great result - well done.