bika

Hi People,

New to this site & forum, but not new to Mustangs ! Have a 1990 5.0 LX, .Was bought new by a family member in 1990 . Been having a electrical drain,pulling down battery . Bought a new battery,& dead a week later. Replaced battery,and installed new alternator . Alternator is charging battery fine. However, still , something is pulling a drain on battery while engine is off.

Brought vehicle to two different electrical mechanics. First guy says radio was pulling too much parasitic power.So, disconnected radio & fuse .Ran well for a week,and now dead battery again . Replace battery again.

Second mechanic says, yep, definitely getting a drain somewhere. So he checks vehicle for a couple days (no onboard computer),and says sorry,can't find the drain,you may have to leave it with me 3-4 weeks @ $119.00 per hour. NOT...

Anyone had a similar situation,or have any clue as to what could be causing this parasitic voltage drain ? I have replaced every electrical part under the hood ,and some parts twice .

Any help, or advise would be greatly appreciated

Thanks, Bika

mongolchuck

A simple but often overlooked cause could be the glove box light.

dawson1112

Get yourself a digital multi meter capable of reading milliamps.
Pull the negative terminal from the battery and measure the milliamps that are being drawn across the loose end of the cable and the negative batt. terminal.
If your getting a high milliamp reading , start pulling fuses till you find the one that stops pulling power. That would be your culprit.

Also just because the alternator is charging does not mean its good. A shorted diode can draw power across it.

88 orangepeel notch

My car was doing the same thing, low battery after 3-4 days of sitting. I did what Dawson suggested. Thru a multimeter across the battery and started pulling fuses. Turns out it was in my cigarette lighter that was causing the drain. I'm no electrician, but it was very easy to check. Good luck, and post back when you find the culprit.

mjr46

set the dvom to the amps setting not the millamp setting if the dvom has such, to many make the mistake of setting it on the millamp setting and pop goes the fuse for the millamp setting if drain is over what that setting can handle

Maxwelhse

Get a decent meter capable of reading AMPs, wire it inline with your battery's positive terminal, and start pulling fuses until you find the offending circuit.

Tregge

There are a lot of videos on how to do the acidic draw test safely without killing your multimeter. Just search how to fix a acidic draw.

mjr46

hrmmmmmm that acidic draw test may kill the meter either way.................acid on a meter = bad ...lol

bika

Vanity Mirror Lights on passenger side were on 24-7 .I never sit there,and have never used the visor much less the vanity lights or mirror on the passenger side. Caught a tiny glimpse of light & found it. There were 7 accessories on that fuse,so ,even though I pulled the fuses ,as did two mechanics,the drain was never found,until yesterday,by me,quite accidentally. Thanks for all the help & suggestions people !

Maxwelhse

I suppose no one mentioned it, but if you're showing more than 1-2A draw pull your meter immediately... THEN pull a fuse one at a time, rechecking with the meter briefly connected, until you find the circuit.

My $100 Craftsman meter is good to 10A constant, 20A peak, and is fused. Good enough for me!