Out of the blue the battery on my 71 started to go down in a day or two without being driven. In checking this out I have determined there is a 2.8 amp drain at the battery with the key off. Further checking shows .15 volts drain at the heater fuse terminal in the main body wire harness fuse panel. All other (not ignition keyed) terminals show no voltage.
Also, with the key on, there is a .4 volt variance between the right and left side fuse terminals in the fuse block. The heater fuse is on the right side.
Any ideas?

 

Unhook the battery and make sure the battery is good?

 

Go back to your 2.8 amp drain at the battery and work from there.If you remove the heater fuse does this 2.8 drain go away?

 

Removed the fuse, drain still exists.

 

well, same test, start pullin fuses until it does go away. Doors closed, lights and keys off.
Usual culprits are the alternator, interior light timer, horn circuit, alarm.

 

Put some duct tape over the interior light switches on the door jamb so you can work with the door opened. The interior lights will draw some current; were those ON when you did your checking?

 

No, I have the courtesy lights fuse pulled.

 

I believe the culprit has been identified. I have .13 volts at the unswitched side of the heater fuse clip, when it should be zero. Question is, where can it be coming from?

 

Alternator or light timer

 

.13 on the cold side? 12v on 1 side and .13 on the other?Pull the plug off the fan switch and see if that stops it.
Have you replaced a starter recently?

 

OK This is why I hate these mother fu^%&*($&* son of a ^**^$&* bitc%%^&^&** digital volt meters when trying to hunt down a battery drain...............SOB... That is normal .13 on the cold side is normal.Why ? hell I dont know but I went out and check one I have in the garage and it measured .12 on the cold side and 0 on the hot when the key is off and 12+v when the key is on.You need to measure your draw at the battery using the amp scale or a test light.Here is a test below thats pretty easy to follow.It should narrow this down to a certain circuit.Then we can help you from there.
Sorry about all the cussin !!!!!!!!!!!!!

Battery Drain Test-easy to do with pics

There seems to have been alot of battery drain issues lately.Thought I would write down this fairly easy way to check for battery drain and share it.All you need is an inexpensive 12 volt test light and a short piece of wire. A test light like this one will be very useful for other 12 volt electrical issues.When you go to this link put in your Zip code. http://www.partsamerica.com/productd...egoryCode=3391 Use a bulb type of test light for this test procedure not an LED type.

If you have a C3 and “DO NOT” have delayed courtesy lights and your courtesy lights work this is “my” way to check for battery drain Put both windows down and make sure everything is turned off. Disconnect the negative battery cable and put your 12-volt test light between the (-) battery terminal and the (-) battery cable. Here is a picture to help. With the driver’s door open the test light should be lit. Make sure everything is turned off and close the driver’s door. Wait several minutes (clock step). If the test light stays out completely (no low glow) you have no battery drain.
If the test light is on or even a low glow you have a drain on your battery. (bright bulb is heavy drain ,dim bulb is low drain) First thing I do is push on the doors and watch test light then lean in through the window and push on things with lights like the glove box door, visor light, map lights and the rear center compartment and watch to see if test light flickers or goes out if so you have found your drain. Second thing I do is open the drivers door and remove the courtesy light fuse, if the test light goes out then the drain is in the courtesy light circuit. If the light remains lit continue to remove fuses until the light goes out and that will be the circuit with the drain. If the test light doesn’t go out then the drain is in a circuit not protected by the fuse box.

“Clock step” Info-clocks can be a pain.
Above when you closed the door if the test light went out but came back on shortly afterwards it’s the clock trying to wind and its drawing too much. Disconnect the power to the clock and retest.

If you determine your draw is in the courtesy light circuit disconnect the power to the clock and retest. If this doesn’t eliminate the draw you can now move on to other items on the courtesy light circuit.

OVERNIGHT CLOCK TEST-I use this alot on mechanical clocks on cars that have intermittent power drains.Leave test light hooked up as above and let clock continue to run through the test light all night.If you come out in the morning and the light is off then the clock is in good shape.If the light is on the clock will have stopped and you should have the clock checked or replace it.

 

.13v on both sides with key off. .13v on right side only with key off and fuse removed. 13.5v on both sides with key on.
Had the alternator rebuilt (original alternator) about one month ago.

 

I have a 2.8 amp drain with the battery disconnected and hooked up like you show in the picture. That's probably enough to run the battery down in 24-48 hrs. I'll continue with your recommended checks tomorrow.
Did you have the .15 v on all cold side terminals or just the heater fuse?

 

I'll disconnect the alternator and check tomorrow, as I recently had it rebuilt.