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It seems through design and or faults/ poorly adjusted switches etc the 964 will draw a significant current from the battery even when the ignition is off.
During my refurb I wanted to remove the chances of this drain as much as possible, save a little weight and make the car more reliable.
The only drain I have now is my aftermarket alarm and tracker, and my windows open all the time instead of having a mind of their own. The car has been 100% reliable and I run an RS size battery (10.5kg instead of 18.5kg).
2. removed the window relay and replaced with a link plug, this relay is linked to ignition/door switches and can be energised after the ignition is off/stay on. I also got fed up with turning on the ignition just to open the windows. The link removes this drain and makes the windows permanently live.
Link part no 964 610 184 00
3. unplugged the washer jet heaters, the screen wash jet heaters are permanently live when the ignition is on!! no point, the frunk is not heated and will freeze solid anyway and why heat your jets in the summer lol. Unplug, tape over connectors and cut off the wires at the washers (weight).
4. Removed the frunk light switch and metal actuator plate (and also the metal plate at the inner wing (weight) Switch can be stuck on/corroded, unreliable - delete and have no light, or I am going to fit a 996 frunk catch with built in switch, this switch is in the catch mechanism, just needs wiring up and the cable adapted.. For now I have no light.
5. removed the glove box switch (weight) and wired the glovebox light to the door switches - known issue with it staying on, now it comes on with the doors, great as you get extra light in the passenger footwell, still can be "rocked" to be switched on individually if needed.
6. removed any unused clock warning lamps - known issue drain, just take out any not used easy to do.
7. removed all of the factory alarm/immo - known drain, very easy to bypass for any thief and only operates on the door switches so not exactly secure. Remove and all wiring, units, loop the immo lines and remove the alarm wiring and horn under the wing (weight). Replace with catI alarm immo.
8. replaced all interior lamps and dash centre console lamps with LED - (reduce drain).
9. cleaned all the earth points I could get to. (there are 20 odd ! ) know issue for drain/reliablity, just do them all as you go round the car.
10. unplugged and cleaned all connectors in the frunk - abs,etc, there is moisture in the frunk all year, just unplug everything, ABS controller, ABS pump, etc clean and re connect.
11. removed all relays/DME/rear window heater/spoiler controller/central locking control/etc, took the covers off and re-soldered all of the connections/pcb pads - not difficult to do, just lift off the covers with a small screwdriver, and re-solder all the tracks and pads. This includes under dash, under seats, in engine bay and frunk fuse boxes.
12. Deleted rear engine bay aux fan and fitted cup bypass pipe, carried out relay bypass mod. I have not noticed any difference in heat at all and I run a Targa all year. (weight/battery alternator load reduced)
13. Delete headlight washers, washer tank under wing, relays, wiring. Use high intensity washer tank for screen wash, just re-wire to washer stalk. Remove intense washer relay and wiring and pipework and one way valves. (weight/reliability)
14. replace stupid clown horns and brackets under wing, with bosch mini dual tone lightweight horns. (weight/stupid clown sound)
15. Open up the wiring looms in the car and remove any unused wires, all the 964s have the same looms, cabrio, targa, coupe, so there are many unnecessary connectors and wires throughout. If you get the chance remove/bypass any unused by referring to the wiring diagrams. I removed all - cruise control, sunroof, cab hood, speakers, heated seats, etc (weight)
16. Convert to HID headlights, 35watt, straightfoward and I have a good cutoff pattern, less drain and now they are via a relay instead of through the stalk switch which is known to burn out. (drain/reliability)
17. functional change - re-wire the cigarette lighter socket to perm 12v - a small wiring change under the fuse/relay box in the frunk - USA version is perm 12v, ROW is switched, not great if you want to charge phone/sat nav etc.
18. Functional change - Independent rear fog switching - the front and rear fogs are linked, a small change under the relay/fuse box makes them switch on their own, good if you want just them on or have deleted the fronts.
Thanks chaps, I just used the porsche wiring diagrams (maint manual vol7 I think?) it used to be on line to download.
I will have to measure it now, first connection the tracker battery and alarm battery draw a charging current, so the reading is higher, I need to do a longer test to wait for it to settle.
True enough they aren't expensive mods and more for reliability than anything! good odd jobs to do over the winter
The fans in the dash still pull the air from the rear, and the engine mechanical fan still pushes. Providing your flappers are working and hoses in good condition heat is fine.
The fans in the dash still pull the air from the rear, and the engine mechanical fan still pushes. Providing your flappers are working and hoses in good condition heat is fine.
Didn't know that... looks like I'm about to shed 10 lbs !!! Thanks!
12-06-2015, 08:18 AM
DIY - Reduce unpredictable battery drain
