Battery Draw and Tach problem

[halfbroken]

Hey, I'm new around here. Couple weeks ago I got my first 325Is. It's nice, but the battery and the Tach has problems.

Battery Problem:
Every 5 days or so without driving the car the battery is dead. I've done a search and found that ppl had dead batteries within hours. Mine slowly dies over days. What could be causing this? Here are some factors i've considered:

1) One of the fog lamps is totally rushed out
2) The stereo is aftermarket
3) The dash has no lights that work
4) Both the interior lights are out

I don't know what else. And to top it off, i'm a totaly noob with electrical stuff.

Tach Problem:
The tach will only work on very cold days, otherwise will not work at all. Everything in the cluster works. Any suggestions?

Any help would be great. Thanks

[88325isboy]

Check glove box light and trunk light those are big ones that make it have a draw.

[Anthrsckmnd]

^ Glove box and trunk are likely culprits. I was having the same problem and it turned out to be the motor in the power antenna. But currently I'm having problems with my tach. First the tach and temp were dead, so I swapped in new si batteries and the temp guage came back to life but still no tach. I have the coding plug in the front, and visually it looks good but if it went bad, could that be why the tach is dead? Also, when I turn off the car, about 3 seconds after it's off, the tach needle jumps to about 300 rpms for a split second, so it seems like the tach is getting power it just refuses to work. Anyone with any similar experiences/ideas??

[rede30]

3) The dash has no lights that work

replace the head light switch, all my lights stopped working and it was just the knob. Pretty cheap too. Get a test light, hook one side to the battery and ground the other. The light should light up and then just start pulling fuses till the light get very dim. It should always be on because of the radio and other memory things but it shouldnt be bright.

[jht3]

replace the head light switch, all my lights stopped working and it was just the knob. Pretty cheap too.

same here, but more accurately it is the rheostat (or dimmer to the layman). basically it is a resistor and when broken, there is no path to ground. i fixed mine by putting a jumper wire across the two pins at the back of the switch. 2 years later and i still havent' replaced the switch :)

[StereoInstaller1]

Battery draw test:"Okie" style...

Find a decent "light bulb" style test light. Charge the battery fully.

Turn off everything in the car. Remove the dome light bulbs, and the key.

Disconnect the positive lead of the battery. Connect the clamp of the test light to the battery, the probe to the positive wire...so the test light is a jumper between the cable and the battery.

If the bulb is lit, you have a draw. Start by pulling fuses, one at a time (replace after no changes) until you find which circuit pulls power.

Remember, there is a relay that controls the dome light circuit, below your left front speaker. This will show a draw whenever your doors are open, assuming your door switches work.

When you get to the point where the light bulb is hard to see if it is on, you should be withing acceptable specs.

During this operation, DO NOT attempt to turn the key on, OK? Fair chance of roasting your ECU due to current starvation, you will cause excess carbon on a few different relays in their attempt to close, just leave the keys on the seat, OK?

HTH,
Luke

[porsche gt1]

Battery draw test:"Okie" style...

Find a decent "light bulb" style test light. Charge the battery fully.

Turn off everything in the car. Remove the dome light bulbs, and the key.

Disconnect the positive lead of the battery. Connect the clamp of the test light to the battery, the probe to the positive wire...so the test light is a jumper between the cable and the battery.

If the bulb is lit, you have a draw. Start by pulling fuses, one at a time (replace after no changes) until you find which circuit pulls power.

Remember, there is a relay that controls the dome light circuit, below your left front speaker. This will show a draw whenever your doors are open, assuming your door switches work.

When you get to the point where the light bulb is hard to see if it is on, you should be withing acceptable specs.

During this operation, DO NOT attempt to turn the key on, OK? Fair chance of roasting your ECU due to current starvation, you will cause excess carbon on a few different relays in their attempt to close, just leave the keys on the seat, OK?

HTH,
Luke

remember though with this test to make sure you either press the button for the trunk light or take the fuse out for the trunk light. Otherwise the light will always stay lit. This is a very effective test for testing a parasitic draw. I have use it may a time.

[euroshark]

I dont think my '84 has a light in the trunk, but my battery dies after about 4 or 5 days as well... Today it was at 1.8v...

I think it's time for a new battery...