83 944 porsche something is draining my battery overnight.always dead. heard aftermarket radio needs wired straight to ignition? when I put key in without turning it on radio and blower works. engine fan stays running even with battery completely dead.

If the battery goes dead overnight with a 80mv drain you have a bad battery, the radio, clock and ECM along with other electronics all draw a small amount of current in order to keep their memories.

So what does your mechanic think is wrong ? Battery dies overnight while sitting or when driving the battery goes dead ? Two different problems . Going dead overnight means there is a parasitic drain on the battery . ( something is staying on ) Going dead while driving means the alternator isn't charging the battery .

If the only issue with the radio is that it will not turn off and then drain your battery, I would locate the power wire to it and put an on/off switch on it to manually do the deed . Repair not cost effective. Make sure it is the radio responsible for the drain. Use an ammeter to check power usage with ignition off and radio connected and disconnected to just make sure.

You haven't given a lot of information to go on and I don't really get what you mean when you say the battery is dead even when the engine isn't running.

Have you had the battery tested? Most any parts store or repair shop can test a battery for you and tell you if it's good, bad, or just needs charging.

If the battery checks out okay poor connections at your battery could be the problem or the cables themselves could be so corroded that they no longer are capable of flowing current. If there is corrosion on your battery terminals that is a place to start. Use baking soda and water to clean the clamps and posts (you'll want to remove them for this), also a wire brush for tough spots.

Does the battery go dead after a few days or overnight? If after a few hours or overnight then something is most likely draining the battery. Do you have to jump start your car after it sits for a few hours? If so then look for dome or glove or trunk lights being left on, brake lights sticking on, aftermarket stereo or alarm wiring issues, or other items staying on after the car is turned off that would drain the battery. Bad door or trunk switches for the dome lights can cause the lights to stay on.

You can test for ignition off draw with the right testers to see if it's within specs. You could also pull the IOD fuse in the block under the hood to see if that stops the battery from going dead overnight.

If it goes dead over the course of several days then a more likely suspect might be the charging system.

But these are all just general ideas. We need more specific information to really hone in on any one area. But the first thing to do is get that battery checked and given a clean bill of health.

turn on the ignition. if the yellow gets power with the key on, and no power with the key off, it connects to the yellow on the radio. Yellow on the radio is for memory power, to remember your presets and clock.

All aftermarket radios now are all the same when it comes to wiring colors.

black is always common, or ground for all aftermarket radios.

Maybe the alternator is not charging the battery up well. To test, put a voltmeter on the battery, engine running. If voltmeter is less than 13.5 volts, suspect a weak alternator-have it tested.
If charging system and alternator is good-charging between 13.5 volts and 14.5 volts, have the battery tested. Even though not old, it may have a dead cell. A parts store can load test it and see.
If battery and alternator are both good, you may have an unintended drain on the battery. You can check this by, first charging up the battery, then leave the negative terminal off the battery overnight. If it starts good next day, there may be a drain, something like a glove box light, an under hood light, a radio amp left on.
Post back if you want help with finding an unintended drain.

You'll need to have someone check for a battery drain.
Something in the car is using electricity when the key is off, or the battery has an internal short and is draining itself.
If you disconnect the battery overnight and it is still dead in the morning, you need a new battery.

you may have something draining the battery a bare wire touching something, check all of the lights , trunk,hood, glove box to make sure they are all off try disconnecting a lead from the battery overnight to see if the battery still is dead in the morning, if it doesn't go dead you will have to try and find out where the problem is .....hope this helps......cheers.

both,the battery has been run down too many times and your radio have a heavy power draw,if you have an aftermarket alarm it may have something to do with the problem.

do I need a a microship in my porsche key?