Battery Drain-Isolated Fuse-Now What?

[mfisel]

I have a 1983 300D that was showing about a 1.5 amp battery drain. After pulling fuse #2 (Radio, Power antenna, dome light, etc.), everything normalized. I unhooked both the aftermarket stereo and amp, but this didn't resolve the problem. From what I've read, the antenna may be the next likely culprit, but is it best to unhook it directly from the motor, or somewhere else?

Also, I just had the stereo and powered subwoofer installed-everything turns off with car, so not running on constant power. And, as I said before, unhooking all of this did not resolve the battery drain. Stereo installers insist that nothing within wiring could be causing battery drain, but does anyone else disagree, or have other suggestions?

Thanks in advance for your help!

[Yak]

If it was fine before the radio/sub install, then they probably tapped off of fuse 2. If they tapped the powered sub off the antenna power line into the trunk (fuse 2) then it always draws power. The antenna trigger line into the trunk only has power with the ignition on. Think about a basic action: the antenna motor runs with the key out when it retracts, so it's hot to the battery.

Does the amp and/or sub have an "always on" power requirement? If not, I'd recommend a relay that uses the antenna trigger to to close a separate fused line to the battery. You may be able to use the antenna power supply in the trunk as a source, but you're now pulling extra juice through an old wire.

[mfisel]

OK, so even though the drain was happening while I had the sub disconnected from the battery for several days, this could still be the problem?

[RML]

I had this problem and isolated it to fuse #2 as well. I unplugged the antenna in the trunk and the problem went away. I do not understand all of the ramifications of your sound system installation, but unplugging the antenna may isolate the current drain.

[Oldwolf]

I just had a situation on my W124 where the dome light/seat belt warning lamp was staying on. Have you checked yours? Even if the bulbs are removed would there be a ampere drain if the dome lamp module was malfunctioning?

[vstech]

have you opened the antenna and looked at the condition of the internals?

[LoosBenz]

Originally Posted by mfisel

I have a 1983 300D that was showing about a 1.5 amp battery drain. After pulling fuse #2 (Radio, Power antenna, dome light, etc.), everything normalized. I unhooked both the aftermarket stereo and amp, but this didn't resolve the problem. From what I've read, the antenna may be the next likely culprit, but is it best to unhook it directly from the motor, or somewhere else?

Also, I just had the stereo and powered subwoofer installed-everything turns off with car, so not running on constant power. And, as I said before, unhooking all of this did not resolve the battery drain. Stereo installers insist that nothing within wiring could be causing battery drain, but does anyone else disagree, or have other suggestions?

Thanks in advance for your help!

Yes, disconnect the power line to the antenna motor.

[mfisel]

OK, looks like next step is to unplug power directly from antenna motor. Is it difficult to access through the trunk?

Thanks again for all of the helpful input!

[RML]

All that is involved is pulling back the plastic trunk liner. Very simple.

[mfisel]

Got it-Amps went from 1.5 to .18 after pulling the antenna, so I think it was the culprit (hopefully .18 isn't high enough to cause a problem).

[Yak]

Antenna may not have been sensing it was "parked" when fully retracted. Like vstech advised, check the internals, clean and reinstall, then check current draw again. There are some other threads where people have measured 'normal' current draw. Try a search for milliamps or milli-amps to look for other data points.