1st Boxster, 1st Problems

[Stuart Waite]

Hi Guys
I have just bought my wife a Boxster for X-Mas to replace her beloved MGF
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
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 batter 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 ?
Cheers
Stuart
Ludlow
Ocean Blue 2.7 986 2000YM

[tr7v8]

Stuart sounds like a CANBUS controller issue to me & will need scanning & investigation by someone with a PWIS or similar.
A quick question is the carpet dry inside? Especially under the passenger seat? There is a body control module there & if the drains are blocked it'll get a bath which it doesn't like.
Worth trying a battery disconnect & reconnect to see if it'll reset.

[Stuart Waite]

Hi Jim
Thanks for your reply
Carpets are all dry and have reset the canbus - still the same
Got any ideas what else is on the E3 fuse circuit?
I have an OBD2 reader - do you know where the data port is on the Boxster?
Cheers
Stuart

[tr7v8]

986 OBD port is just above your left knee when sat in the passenger seat IIRC.
According to the wiring diagram E3 is left seat heating & left backrest motor. It doesn't feed these direct it goes to CU Module Left M537. At that point I cannot find any more. If you have a hunt around you can download the full manual (genuine) from either Porsche or a shadow site.

[Chris H1]

In the Bently Service Manual it lists fuse E3 as "Seat Back Control Left, Seat & Mirror Control Module" if that helps at all. Seat position & memory module is located under the drivers seat (not sure if there will be one with your car not having said memory option). As Jim mentions in his first post the first port of call for Boxster electrical gremlins is check theres no damp any where (get your self a trombone cleaner & check all your drain holes for roof & front scuttle/battery area). Does the drain stop if you remove the E3 fuse?

Be careful if you dissconnect seat electrics for any reason as if you turn the ignition on whilst they are dissconnected you will get a light on the dash that the majority of code readers cant reset.

HTH

[Stuart Waite]

Hi Chris
The car is in lovely original condition - as far as I can tell! It seams watertight and nice and dry
It has manual full grey leather seats without the heating option.
Fuses E3 & E4 are both 30A and should be for seat positioning/memory so are not in use on this car
As a temporary fix I have removed E3 and the dark current has dissapeared and everything seams to be working fine. No warning lights or ecu/canbus errors

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

[Chris H1]

My seats on my 2003 model are manual with no heated parts (they have now after I fitted an after market kit) but the back tilt adjustment is electric so are yours the same as thinking out loud there could be a drain if the switch was shorting/stuck in position some how? E3 is fuse for the left seat & E4 is for the right hand seat.

[Daz85lux]

That could be exactly the problem Chris.
Mine had a serious drain on fuse E3 which turned out to be a faulty seat switch.
Luckily I had a spare set of complete seats in the garage.

[Stuart Waite]

Bingo

Well done Chris H1 and Daz85Lux you are both correct.

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.
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.

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

Cheers
Stuart

[Daz85lux]

A nice easy fix for you Stuart!
Mine was exactly the same when I first bought it
as neither of my seats would adjust on the switch.
Glad you got it sorted.

[Chris H1]

Excellent news & its good to see more folk posting/answering in the Mid Engined section as it gets a bit quiet in here sometimes

Glad its fixed now get it out driving & don't forget the roof must be down at all times

[Guvs]

I love happy endings
Guvs.