Electrical Parasitic draw...

[DRTHWKR]

I recently picked up an '80 CJ5 2.5l from the second owner, who essentially knew nothing about the vehicle; it was a gift to him and he only drove it a few times.
There seems to be some sort of parasitic draw on the battery. Battery had a full charge and a week or so later, completely dead. Nothing left on (lights, radio, etc).
Battery is 6 months old, terminals are clean and cables tight.
How can I track down the source of the drain?

 

[CJ]

The cheapest way is with a good old fashion test light (incandescent bulb - not LED). By placing it inline in any circuit, just look for a slight glow. Start from the battery and work back.

Test light

Google Search

If you want to spend a few $ to add to your tool collection.

Power Probe

Google Search

 

[KRUPP]

Annoying, right? Pretty common in older vehicles and especially Jeeps. Add all the various accessories we tend to wire-up (off road lights, updated ignition, fuel injection, winches, stereos, CBs, amplifiers, accessory 12v plugs, etc.) and the chances get greater for a problem.

I spent about an hour trying to find the voltage draw I was experiencing. No luck, except for the obvious draw from the dash clock.
I decided to add in a battery disconnect for the time being. It goes on the negative battery post and is a simple screw on/screw off disconnect.

BATTERY DOCTOR Battery Disconnect Switch: Top Post Rotary, Top Post, Negative, 12V, 500 A, Zinc​

Item 4NGU3
Mfr. Model 20308

 

[Belizean]

Annoying, right? Pretty common in older vehicles and especially Jeeps. Add all the various accessories we tend to wire-up (off road lights, updated ignition, fuel injection, winches, stereos, CBs, amplifiers, accessory 12v plugs, etc.) and the chances get greater for a problem.

I spent about an hour trying to find the voltage draw I was experiencing. No luck, except for the obvious draw from the dash clock.
I decided to add in a battery disconnect for the time being. It goes on the negative battery post and is a simple screw on/screw off disconnect.

View attachment 103602

BATTERY DOCTOR Battery Disconnect Switch: Top Post Rotary, Top Post, Negative, 12V, 500 A, Zinc​

Item 4NGU3
Mfr. Model 20308

Wonder how that would work as a theft protector ? Someone pretty smart might figure it out pretty quickly.

 

[DRTHWKR]

I appreciate the input- I may and up doing both- one to hopefully resolve the issue, and the other to prevent it!

 

[TeamRush]

Multimeter, the cheap ones will do just fine.

Remove the negative terminal from the battery and connect the multimeter, set to volts, between battery terminal and negative cable.

You CAN add long wires to the battery and cable so you can see readings while pulling fuses, chasing the issue.

Where I would start is with the Alternator. A bad rectifier diode will still charge the battery when running, but will drain the battery when parked.

Do the connection above and disconnect the alternator and see if voltage moving through the meter drops off.

If it's not the alternator then move to fuse block, pull fuses one at a time and look for drop off in voltage. 99 times out of 100 you will find the circuit with faulty circuit/component this way.

The only device that won't have a fuse is the headlights. The breaker for the headlights is in the headlight switch. To test headlights/headlight switch for power drain pull the connector off the dimmer switch. Both bright & dim power go through the dimmer switch.

On the positive battery cable side of the starter relay you will find two smaller wires, 10 to 12 AWG.

There will be ring terminal, 4 to 6 inches of rubberized insulation, then a plastic block about 3/4 inch long. The regular vinyl insulation wire will come out of this plastic block.

These are NOT regular wire, these are fuse wires called 'Fusible Links'. Fuses protect the WIRE, not devices. There are here to protect the wire in the event that wire gets pinched or otherwise 'grounded' out.

One of these fusible links will go to the fuse block, the other will go to the alternator.

If you remove these smaller wires from the starter relay then connect the battery cable back to the starter relay this will test the starter relay.

This assumes a previous owner didn't cobble something into the system somewhere.

 

[DRTHWKR]

Multimeter, the cheap ones will do just fine.

Remove the negative terminal from the battery and connect the multimeter, set to volts, between battery terminal and negative cable.

You CAN add long wires to the battery and cable so you can see readings while pulling fuses, chasing the issue.

Where I would start is with the Alternator. A bad rectifier diode will still charge the battery when running, but will drain the battery when parked.

Do the connection above and disconnect the alternator and see if voltage moving through the meter drops off.

If it's not the alternator then move to fuse block, pull fuses one at a time and look for drop off in voltage. 99 times out of 100 you will find the circuit with faulty circuit/component this way.

The only device that won't have a fuse is the headlights. The breaker for the headlights is in the headlight switch. To test headlights/headlight switch for power drain pull the connector off the dimmer switch. Both bright & dim power go through the dimmer switch.

On the positive battery cable side of the starter relay you will find two smaller wires, 10 to 12 AWG.

There will be ring terminal, 4 to 6 inches of rubberized insulation, then a plastic block about 3/4 inch long. The regular vinyl insulation wire will come out of this plastic block.

These are NOT regular wire, these are fuse wires called 'Fusible Links'. Fuses protect the WIRE, not devices. There are here to protect the wire in the event that wire gets pinched or otherwise 'grounded' out.

One of these fusible links will go to the fuse block, the other will go to the alternator.

If you remove these smaller wires from the starter relay then connect the battery cable back to the starter relay this will test the starter relay.

This assumes a previous owner didn't cobble something into the system somewhere.

Thank you!

 

[Lumpy Grits]

Disconnect the alternator and see if it stops.
How long from full charge does if take to get to a no start?
Have the battery load tested. What's the CCA of this battery.