Fireball57

'80 L-48. Trying to track down a battery drain. I have a cut-off switch but I'd like to isolate the problem. I hooked up a circuit tester between the battery and ground cable, with doors shut and window rolled down and the tester light came on. What I immediately noticed was the faint sound of a "thump, thump, thump" from the fuel tank area. Almost sounds like a really quiet electric fuel pump or an in the tank fuel pump. Just bought the car 3 weeks ago so I got under the car and the mechanical pump is in place and plumbed to the carb. What is making this sound like a heartbeat?

FourG

Newbie here, but hey, an idea's an idea (and the old guard will promptly bludgeon me with a Clue-By-Four if I'm right out): do you have a power antenna? If so, maybe something's got it trying to retract repeatedly and hitting a stop when power's connected?

I have a drain issue myself on my '76, but I think it was thanks to user error (I left the convenience lights on after messing with the headlight rheostat - still getting familiar with the dash).

Fireball57

Thanks newbie! As am I. You were absolutely correct. Pulled that fuse and it stopped. Aftermarket stereo not working but relocated that wire to another ignition circuit and all is good. Will leave it on the battery and see if that was the only parasite. Thanks again!

Roughrider

Check and see if the convenience light timer is bad. That's a not uncommon problem after so many years. If the timer goes bad the interior lights will not go off after 20-30 seconds like normal. It can even cause the lights to come on at odd times.

If it is malfunctioning, it should be located under the dash behind the glove box...it's orange with wires that plug into it.

Fireball57

Would that be the same fuse I pulled for the antenna? Courtesy/clock etc.

Fireball57

And to unplug my power antenna for now, is it under the armrest or under the storage compartment?