Gentlemen,
My 88 very will sit forever and restart as long as the 20A fuse for the horn, door locks, radio, etc & and about 6 other combined factory circuits is not installed.
Otherwise, more than two days requires a jump.
All of the 20A multiple circuit's wires congregate behind the dash, not numbered, and all yellow unfortunately.
Any ideas on isolating this one slight millivolt drain?
Thank you.

 

A big culprit is usually the cig lighter. If you have a digital multi meter, you could connect it to the battery and plug in a fuse one at a time till you narrow it down to one circuit. I have never heard of all circuit wires being all yellow.

 

Factory wires in that circuit are orange, not yellow.

Sounds like a radio or alarm installer has left behind a gift that keeps on giving somewhere.

That's what I'd be looking at... improperly wired radio, amp, alarm, or other aftermarket add-on.

A battery drain isn't millivolts; it's milliamps. (or even, whole amps)

 

I'd def be looking at the radio stuff as a start.
On the birds, I've had the console light switch get stuck on and drain the battery

 

Sofa,
Right again.... Milliamps. Well, duh. Oops.
Yes, it does have an aftermarket stereo AND an unused alarm system.
"Gift that keeps on giving" lol
Thank you all for the replies.

 

Check the "trunk" light also to make sure it hasn't been left on.


You can do an "amp draw" test by using a multi-meter set on amps.
Disconnect the battery positive and put one probe on the battery terminal and the other on the positive cable so you can monitor how many amps or milliamps is being pulled through the cable. One by one, pull your fuses and look for the "draw" to go away or partially away. This will at least narrow down the particular circuit that the parasitic draw is on and you can then narrow that down more by unhooking things like the lighter, overhead light, console light, etc etc.

 

From the factory the Yellow wires are the Airbag system (Safety Restraint System) so be careful about working with Yellow wires behind the dash.

 

The OP's car is a 1988, they didn't put air bags until 1990. I think his orange wires went yellow on him from UV light.