quattro004

I had this problem for close to 4 years now. I have posted on it before but found a few new things this time around. Recently replaced my alternator because old one was going bad. Originally thought the diodes in the alternator were draining power while the car was off. But car was dead after sitting three days last weekend.

Checked drain on negative batter wire. Read out at 100 milliamps which is normal. I have a sub with a cap in back so checked the ground going from the capacitor to chassis and it read 1.8 amps! Sub amp read .5 amps. Both are considered excessive according to repair manual. How is it that these seem to been draining and the main negative battery wire up front shows normal rating??

Anyone have ideas? Or know what I can do to solve this. Don't want to have to start my car everyday again this winter to keep it running...

'96 A4 2.8...

computrtutr

For the power supply to your cap, install a switch that relies on the radio being on (or perhaps the car's switched power). This way, your capacitor will not drain the battery when the car is off. Sorry I can't be more specific, but it's been a while since I did a lot of car electrical work... let us know if this helps!

AudiMick

Seriously you can't overcome the laws of physics. You must be measuring wrong.

The same current flows through both +/- connections so check both sides of the battery.I think my 96 had more than one black/red wire. The Large red one goes to the starter. If you are pulling 1.8 amps its gotta be coming from somewhere.

Disconnect the amp and drive for a week without your stereo. You can hum a tune or re-discover the lost art of conversation.

If the battery doesn't die you have discovered the culprit, then you can do what computrtutr says to fix it.

quattro004

I honestly don't know how it would be reading like that either that's why I'm confused. I set the multimeter to read out in DCA, clamp around the negative from the capacitor and it reads 1.8 DCA... Compared to the 0.2 out of the battery negative.

Its tough to check because until it gets real cold outside it takes 3-5 days to kill the battery and I usually don't go that long without driving somewhere.

For the turn on lead would I just splice and run it from the positive terminal on the cap to the remote turn on lead terminal on my amp? Seems strange to do it that way because my cap does not have a dedicated turn on lead terminal.

AudiMick

..even when the ignition is off.

It's pulling about 30 Watts from somewhere.

So:

1.It's permanently wired to non switched 12 volt.

2.It's wired to the accessory position but the current is to high and has burnt the ignition swich out. Capacitors can cause as the initial charge current can be high when they are completely discharged.

3.It's wired via a relay and the relay has shorted out as in 2.

quattro004

Attachment is quick write up of the wiring diagram. Pretty standard. Have an inline fuse on positive coming from battery. Cap and amp are both grounded separately to brackets under the rear seat.

Also just checked the cap ground on my friends car who has the exact setup as me and it read the same 1.8 on DCA... Really confused now because his car is the same as mine but does not die after sitting for a few days.

quattro004

Turn on lead also runs from deck to amp. The LEDs on my cap turn off automatically after car voltage stops changing which I assume means it has an auto shut-off feature and should not drain power after car is turned off so no turn on lead running to cap as of now.

AudiMick

Capacitors are passive devices, unless they leak they shouldn't draw current when the car is turned off.

Your diagram shows the amp is permanently powered, so there must be control signal to turn it ON/OFF.

It's probably a much smaller wire that activates the amp.Check your wiring diagram for the amp. Normally the head unit activates it. On my Kenwood (not in my Audi)I have blue/ white wire that can be used to switch on the amp or activate the antenna.

See item 3

http://www.ehow.com/how_5238289_iden...eos-wires.html

AudiMick

With the car off are you still pulling (1.8 + 0.5) Amps.

Those control signals cannot drive a very high current.If you are controlling the capacitor , sub and amp with the head unit you may have overloaded it and it may be on all the time.

Where is the Sub power coming from?

quattro004

Amp in diagram is powering the sub. No multi-channel amp. Ive got a 16 gauge wire for a turn on lead running from amp to deck. should I use a thicker wire or will that not make a difference?