How to track down a parasitic drain?
 

So now that I'm fairly satisfied with where my HX is at, my attention is drawn to my '91 Mustang. The 2 most foremost problems I'm facing are, the parasitic drain on the battery that kills it fairly fast, and for some reason the power locks don't work.

My question is, how do I find this parasitic drain? How does one go about tracking it down? I have a feeling it might be the alarm systems fault. But the remote start works just fine, however, it won't arm. Any ideas?

Try measuring the current over the fuses with everything off.

How? Do I pull the fuse and hook up a multimeter to the contacts?

Yes.

Blade types don't need to be pulled. I prefer to leave everything as undisturbed as possible to prevent self induced additional problems.

Disconnect the positive cable and put a test light in line between the battery cable and battery. Light on you have a drain even can be faint (the light).

Pull fuses until the light goes off and the last fuse pulled is the circuit that is causing your problem, but keep pulling fuses until you have pulled them all, you could have more than one problem.

Doesn't work in newer cars which have continuous drains.


regards
Mech

Well the car has an alarm so wouldn't that mess with it? I know it has a red LED that's on 24/7 on the dash whenever the battery is plugged in.

Car alarm and radio have continuous drains, pull them first. If is real quick like over night just pull one fuse a day, or pull them all and reinstall them. You might even be able to see it just watching voltage across the battery with a digital multi-meter.

Stratus has been dead a few morning over the last 6 months, completely flat by morning. I pulled every fuse that wasn't needed, was ok for a few weeks, then dead again. Cameron (14 yo who drives it) was replacing the radio, next day it was dead again). This time I saw the ignition was in ACC position, but no key.

I'm not sure where all the power is going, I think something draining a good battery overnight would be getting hot enough to start a fire, except for the few things made to take/make heat, lights, rear defrost and mirror defrost.

Since your power locks aren't working properly, that would be the first place (fuse) I would look for an electrical drain. It could be they are stuck trying to lock or unlock and continually pulling power as a result.

I'd use Old Mechanic's method, but with an ammeter instead of a light bulb. That will give you an idea of just how much current is being drawn, instead of "Well, there's some..."

Since you have a drain that can completely kill a charged battery in 24 hours, you're probably going to see more than 1 amp. (Don't many batteries have 60 amp-hours in them?) You want less than ~250 milliamps, I think.

-soD

Or just put a cut off switch on one of the battery terminals which would keep the battery from being damaged, or just pull one of the cables when not in use.

If you suspect a non essential system like an alarm, or power door locks, disconnect it-them.

I ran an 8 track for 5 days on a separate car battery before it had to be recharged. Didn't have time to install it so I stuck the stuff and battery in the back seat and floor, but the surf board racks were brazed to the drip rails to keep them from being stolen.

regards
Mech