986 Battery drain

986 Battery drain

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Discussion

Fonzo

Original Poster:

152 posts

66 months

Thursday 23rd December 2021
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My mum has a 60,000 mile 986 3.2 S, 2003 I believe, and it seems something is drawing power when the car is in standby as it the battery will run flat even after a day of not being driven. I have ordered a clamp on ammeter so I can start doing some DIY diagnostics but honestly I'm not sure what sort of process to follow with this and I'm looking for suggestions.

I don't believe it's the alternator not charging the battery as I drove the car 40 miles on the motorway and the car started immediately after turning the car off, but the next day it wouldn't.

Any suggestions of know issues would be really appreciated. Mum is getting pretty close to just scrapping it, which I think would be a bloody shame.

Scrump

22,944 posts

165 months

Thursday 23rd December 2021
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Many of these have a tracker fitted. At this age the battery built in to the tracker has died and so the tracker constantly draws from the main battery rather than just charging up the internal battery when the car is running.

r.g.

601 posts

219 months

Thursday 23rd December 2021
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I have the same issue on ours at the moment. I'm going to try and find out the issue over the Christmas break.

Things to look at:

Boot and frunk lights - Shut small child in (preferably one who's afraid of the dark) if they scream you know the light goes out. If no child available phone on video record should do the trick.

Alternator - unlikely as a run seems to help, but have heard that the charging capability can drop off at higher revs so need to have a meter on the battery and check there's a consistent charge across the rev range.

It then becomes a process of elimination. Have a meter on the battery and systematically pulling fuses to see if current draw reduces/stops. Good description at this link http://testmeterpro.com/parasitic-draw-test-with-a...

My money is on the radio, but only because I want it to be that as it's easy to change!

Good luck!

KPB1973

929 posts

106 months

Wednesday 29th December 2021
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I've had this twice with 2 different 986s. First time around it was the Tracker, the second time the stereo amplifier.

With the former I just kept it on a trickle charger.

Fonzo

Original Poster:

152 posts

66 months

Wednesday 29th December 2021
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Thanks for the replies, I'll be cracking on this weekend and will update if I find a solution.

Stealthracer

7,935 posts

185 months

Friday 31st December 2021
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My 986S gets a bit dodgy if I leave it longer than about 4 or 5 days. It then either just about starts, or fails to and needs a recharge.

If it does start, a 15-minute run means it's OK for another few days.

Stuart12

75 posts

117 months

Friday 31st December 2021
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I have had one for 3 years with the same issue (2002 986 2.7), as I don’t use it much I replaced the battery with whatever one Eurocarparts had on offer and the problem continued. I eventually switched to a Bosch S4 battery around a year ago and have never had an issue since despite it only getting started maybe once a week.


Bright Halo

3,251 posts

242 months

Saturday 1st January 2022
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Another common fault is the ignition switch. You think it’s turned off but sometimes not. Cheap replacement part but a pain to get at.

ClaphamBoxS

352 posts

71 months

Sunday 2nd January 2022
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Not being funny but you haven’t got one of those Bluetooth adaptors plugged into your AC socket have you?
I used to use one in my S and left it plugged in not realising they stay on and eventually it drained the battery…remembered to pull it out each time after using the car and never had another issue…

r.g.

601 posts

219 months

Tuesday 4th January 2022
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I think I fixed mine over the Christmas break.

I did the test with a multi meter where I removed the battery negative cable, put the positive lead from the meter on the battery and the negative meter lead on the disconnected lead and the meter on Amps.

with everything off and key removed this shows the draw on the battery. Make sure you close the frunk latch with a screw driver or remove the bulb and same with drivers door so you don't get a false reading from those lights.

I then systematically removed the fuses in the footwell one by one to see if the draw dropped. Mine dropped significantly when fuse C7 (I think it was that location) was removed. This fuse is for "terminal X" which is the ignition switch.

As mentioned above, this is a pain to get too. you need to get on your back in the footwell and remove the air vent pipe that runs along just below the steering column. It also helps to remove the drivers side air vent, light switch and the trunking behind it.

With those removed, its a simple case of pulling the multi plug off the back of the switch from underneath, then removing the little grub screws on the switch by going through the hole you now have in the dash. Fit new one and put back together. After that, my current draw was almost zero.

Yours may not be that, but going through all the fuses is a good start. It will identify if it's radio related as well. Mine wasn't!

Semmelweiss

1,755 posts

203 months

Tuesday 4th January 2022
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...and this is the switch replacement. As r.g. says its a contortionists dream to get to.

https://www.amazon.co.uk/dp/B006QY2LG0?ref_=pe_270...

I removed the driver's side air vent and used a very cut down small flat-head screwdriver to access the grub screws. If they have never been removed previously, they will have a small amount of red-enamel painted on them, which you will need to scrape off with the cut-down screwdriver before you can get to the slots (2 grub screws).

r.g.

601 posts

219 months

Tuesday 4th January 2022
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Good point! Forgot to mention the handy paint covering the screw head slots.