Ian A

Hi guys - great forum

I have just bought a '90 C4 and have 2 questions if anybody could be kind enough to assist:

1. When I bought the car, it started fine and drove the 250 miles back home no probs at all, but now, when left for over 4 days or more, the battery flattens to the point where even interior lights dont come on. Is there anything immediate/known that I should check for? (I realise trying to trace wiring issues is like finding a needle in a haystack, but any guidance would be appreciated - and I have already tried a new battery, as provided by my local dealer, with the same results)

2. I am told by my dealer that the car has had lowered suspension fitted, and the wheels are 17". What sort of tyre pressures should be used with them? (the only guide I can give as to the make of the alloys is that they have a "Carrera 4" badge in the centre hub of each wheel - if that helps at all)

Again - any help is appreciated - tnx all

Ian A

GP964

Hi Ian,

Had the same problem with my C2, I followed Adrian's 964 Battery Drain test, using a multimeter connected in series witht he positive cable off the battery and got 7ma reading. then locked the doors and turn on the alarm and started pulling all fuses and relays to see if my reading on the multimeter change, none what so ever. There goes trying to find the drain. I check my battery and it was fine, then checked the charging with the car at idle and multimeter read 13.76 volts, so that was ok. Then I basically gave up, but notice the engine and trunk lights were on even if they were closed. So i pulled out the bulbs and taped up the wiring to them. It's been a week so far and no drain <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" /> .... I had to put up with this problem for 6 months.. geez..

Hope that helps!!!

GP

Bill Gregory

Ian,

If you haven't already, you may want to read the in-process 964 FAQ <a href="http://members.rennlist.com/jfk964/porsche_964_faq.htm" target="_blank">here</a>, which may answer some of your questions (Question 6-6 discusses tire pressures). Also, there are some good 964 articles on tech.rennlist.com.

John Boggiano

Ian, of course you could simply have a knackered battery. It's happened to me quite out of the blue - suddenly the battery just wouldn't hold a decent charge.

Re: tyre pressures, Porsche says 36psi all round for 17", but I run my rears at 40. I found 36 lets the rear wheels move about under heavy braking more than I like.

964s, like other 911s, can heat their rear tyres up a LOT when used hard - something to bear in mind if you track it - keep an eye on the pressures.

DaveK

Hi,
One common cause of battery drain is the light in the luggage compartment not going out when it's closed. Take the bulb out and see if it improves.

Dave
90 C4

johnfm

Ian

light in the luggage compartment (the bonnet!!) was my problem. I disconnected it & never had a problem since. It is hard to diagnose, but a layer of frost on the bonnet helps - if the light stays on you will have a neat circle where the light has thawed the frost.

IanR

I had this, traced to luggage compartment light. Brand new Bosch Silver battery flat in 3 days. You can check if the switch works just by pressing it with the bonnet open - its at the left rear corner of the boot when facing the front of the car. The light should go out - mine didn't, temporary fix by removing the bulb until I get round to replacing the switch.

Regards
Ian

Riccardo

IanR,

Ever seen a dark blue C4 cab around Harpenden? Its my mate's, Mario, just curious if you know him, he's another great 964 fan...

IanR

Hi Riccardo,

No, I haven't seen Mario's cab, but I know of him through seeing his name on the various forums/mailing lists. I've only been a 964 owner for just over 3 months, so not really paid much attention before then. I'll keep an eye out now - mine is a Guards Red coupe if he happens to see me.

Cheers,
Ian

MSchett2

If both the engine and luggage compartment lights are on you might want to make sure the alarm circuit for the radio is good. If the "green wire" is not grounded it will keep those lights on and drain the battery. This will also cause the alarm not work work. There are several posts and a Service Bulletin avaliable to help you resolve this.

Wil R. Ferch

One more thing..
Check the door plunger switch that operates the dome lights. It is "Active" once the car is shut down, but only as long as the door is still closed ( you're still in the car...it allows you to operate the sunroof and power windows with the car shut down). however, this circuit should "deactivate" once the door is opened. Meaning? After you drive the car, shut off and see if you can close/open your power windows. Yes? fine. Open and close the door. Can you operate the windows? No? fine. Yes? Not good...means the "circuit" is still alive when it shouldn't be and has been known to drain batteries in about 1-3 days. Hmmm....
---Wil Ferch ( lurking over from the 3.2 list)

Ian A

Well 1st, let me just say "wow". My 1st post and everyone has been so helpfull!!!! Thanks very much!

I have double checked the front and rear bonnet/boot switches - the lights go out when the switches are pressed. As soon as the issue started, I too bought a brand new Bosch Silver battery to try to resolve it, to no avail.
However, I have not tried removing either of the front or rear bulbs yet, so will try that 1st.

Wil - thanks for that, I'm going to test your suggestion right now - will post my findings.

Once again, thanks to everyone for responding, it is VERY much appreciated

Ian

P.s. going to run with 36 psi front, 40 psi rear and see how I get on for now!

DaveK

One thing - Wil's suggestion about door switch / window power etc. is country dependent. In mine (and some other peoples cars) with the ignition off the windows / sunroof are not powered - unless the door is actually open, then they are. It seems that power while ignition is off varies between regions for some reason.

Dave
90 C4

johnfm

Ian

have you actually done the 'fuse pulling' excercise yet? Check the archives with the handy 'search' feature. Essentially, you need to put a mulit-meter in series between the battery and, say, the neg terminal. With evrything off, you should draw about 20mA (I think, check archives for the actual number). If it is much higher than this, say 200 mA, pull a fuse from the board, one by one, until the voltage drops. This fuse will at least tell you which part of the electrics is sapping the power.

Good luck!!

DaveK

...But make sure you push your luggage compartment switch down or take the bulb out while doing it. Otherwise you'll definitely find that's what is taking all the current.

Dave
90 C4