Battery drawdown in 911 after stereo installation

raj_amin · 10:04 AM

Last December I installed Alpine CDA-9885 CD Receiver in my Porsche 911 myself using the Crutchfield instructions

The original harness was messed up so I bypassed the harness and the amplifier and used speaker wires to connect the stereo outputs to the speakers.

Since then the stereo has been working fine - I just had to re-do power to use constant power - however I am having battery problems.

Car's battery dies / goes too low to start the car on daily basis - I suspected the and replaced the battery twice.

Still even brand new battery does not hold the charge even after charging with a wall charger.

I haven't checked the current draw but it seems too much since it draws battery down overnight. Can the stereo unit be drawing batter down?

Also I admit, during installation - I did not pay attention to +/- terminal / wires for speakers - could that be the cause? I can re-check the speaker leads if that's the case.

Any help will be greatly appreciated

dshepp806 · dshepp806's Garage

The speaker leads would have little to do with your problem (but would contribute to crap sound if connected incorrectly),..especially sense you state she's been installed since Dec. (then, all of sudden you're going through batteries?)

You need to check the static current draw at the battery. See if you're draw is too high, then start disconnecting fuses to ID the culprit.

Yes, the unit could be your problem source,..yes, it could be other sources aside from the stereo unit (door switches, hood switch, glove compartment switch/light, etc.)

I would also check that the alternator is doing it's job, too.

Report back with the data.

Best,

Doyle

911pcars · 04:34 PM

"I just had to re-do power to use constant power - however I am having battery problems."

I believe most amplifiers require a separate 12VDC source - one for "constant power". However, this should only be constant only with the ignition ON. If power is applied all the time, that's the source of your current drain. Reconnect this circuit to the ignition switch or fuse box so only a "Key ON" situation energizes this circuit.

A tell-tale LED light on most amplifiers should alert you to this potential condition.

Sherwood

3.2 CAB · 08-02-2008, 08:54 AM

Most of the higher end and even some less expensive have the amp control circuit built in to the stereo. That way the stereo controls the power to the amp. When the stereo is off, so is the amp, and when the stereo is turned on, the amp gets powered up also. It sounds like you have the constant power going to items that don't, or should not have constant power. About the only thing that requires constant power is the stereo head unit, for it to maintain memory settings and keep the clock correct. The rest should be controlled by the ignition switch position. I believe that you need to re-wire according to the stereo installation instructions, if you still have them. Good luck!! Tony.

dentist90 · dentist90's Garage

Quote:

Originally Posted by 3.2 CAB

It sounds like you have the constant power going to items that don't, or should not have constant power. About the only thing that requires constant power is the stereo head unit, for it to maintain memory settings and keep the clock correct. The rest should be controlled by the ignition switch position.

Exactly. There are usually two dash unit input (+) leads. A yellow, for the clock and memory presets, that requires constant voltage and a red for the head unit itself that is switched with the ignition. If you are also running a power amp it is usually wired unswitched (with a fuse) with a heavier cable to the battery, but it must also be wired to the head unit's remote on wire (usually blue). This will signal the power amp to switch on only when the dash unit is turned on. If you can take the key out of the car and the stereo or amp stay on you may run into this kind of trouble.

signature65 · 08-02-2008, 04:50 PM

I hate to bring this old school trick up for Porsches. But tale tale sign you have a draw is to remove the 12V lead off the battery, wait 5 min and reattach it. If it sparks then you have a constant draw somewhere in your system. If it doesnt then its prob the Alt overcharging and burning up yout batteries.

raj_amin · 08-12-2008, 08:47 AM

Dealer diagnosed the problem with the hood switch - cost $200+ another 200 for instillation.
Hood light was staying on even when hood was closed!!! Got to get it fixed to save battery...

btw - I had bypassed the factory amplifier and hooked up the stereo leads directly to the speakers - since the new head has built-in amplifier- works fine.

Thanks for your leads... Great forum

john70t · 08-12-2008, 10:12 AM

Another way to track down electrical shorts is to disconnect the (-) cable, and put a DVOM meter set to "amps' inbetween the cable and battery.
Then pull fuses until the draw goes away. Somewhere in that circuit will be the problem draw.

(BTW- using the "amp meter" circuit on the meter usually requires switching a test wire to a different plug because of different internal resistance within the meter itself.)