Power Drain

[kdcarman]

I have 1970 440-6 Cuda back from Alan's restoration.

There is a strange electrical problem, basically there a constant drain on the battery.
When I drove it home at night, there was not enough power being generated to keep the headlights and dash lights on. 

We put a meter at the battery and found there is an 8 amp drain with the car turned off.
Disconnected the starter relay and the of course the drain goes away.

What could/would draw 8 amps with the car turned off?
And yes the headlights are turned off.     

[anlauto]

Your warrantee is up

I know the clock draws power ? Anybody have a clue as to how much ?

Check and see if the map light is off .... Does it have a map light  .....Man I restore too many cars

[kdcarman]

Yes it has a map light.
But - something is pulling so much power - the alternator cannot keep the car charged when running/driving.  The map light would not shut the car down while driving.  Hmm?

[anlauto]

I thought we decided the alternator was no good ? Did you have it tested ?

[73_Cuda_4_Me]

 

8 amps is not a 'small' draw! Bad diodes on alternator, shorted windings, and possibly bad regulator (a 'good' 65-amp alternator should be able to run headlamps and charge battery at the same time! Unless you have upgraded headlights and electric cooling fans...

I am pretty sure my 73's alternator connected to the starter relay battery side, so disconnecting it would drop alternator. Can verify by disconnecting battery connection at the alternator to see if draw goes away then... bad alternator if so..

[JS29]

You could try putting A test light across the negative post and cable, A draw would light the bulb. then try pulling fuses one at A time and see if the light go's out. if so you will know what circuit to look for.          

[1 Wild R/T]

As mentioned for a draw that significant first thing I'd look at is the Alternator.... Disconnect all three wires & test for the draw again..... If that doesn't stop the draw as mentioned start pulling fuses .... Remember if the door is open while you test the dome light will be on....  But standard small bulbs typically draw about .3 amps  so an 8 amp draw should be pretty easy to find....

[kdcarman]

Thanks for the input.
And yes I did purchase a new alternator as the most likely place to start.

I did not think a bad alternator would draw 8 amps with the car not running.

[73_Cuda_4_Me]

Diodes usually fail open, but in high-current applications, they can short out, and current limiting is done by winding wire resistance (similar to toaster nichrome wire)... 2 or more diodes gone could reach that much current...

We had a bank of diodes on a 1500 volt power converter for a rail grinder we built for NYCT that shorted out... WOW, what a mess!!!

[Strawdawg]

Sounds like either the alternator or the battery is shorting internally...

An 8 amp draw is going to blow fuses if it is really 8 amps...or it will cause smoke someplace such as the ammeter wiring under the dash.

[anlauto]

Any updates ?

[RUNCHARGER]

Another vote for the alternator.