Battery drain

[drummer97223]

Hello, new member with a 90 LSC. Overnight my battery is drained. I have read other sites but I really don't think it is in the ignition. I have tried the test light test while pulling fuses and no results to the problem. I have a new alternator and battery. If I unhook the battery at night it is fine. Also, the wipers don't work? I have pulled that fuse to but no help. I really need the wipers to work in Oregon winter and would like to solve the drain. Any help appreciated. Thanks

 

[1986_MarkVII]

Don't be intimidated by an ignition switch

Overnight my battery is drained. I have read other sites but I really don't think it is in the ignition. I have tried the test light test while pulling fuses and no results to the problem. I have a new alternator and battery. If I unhook the battery at night it is fine. Also, the wipers don't work? I have pulled that fuse to but no help.

Why do you think it's not the ignition?

Have you checked the key cylinder? A bad one will drain the battery, overnight.

 

[drummer97223]

Is there a way to check it without getting into it? I am tired of buying parts and not getting results. Thanks

 

[1986_MarkVII]

Bite the bullet and buy the parts

Is there a way to check it without getting into it? I am tired of buying parts and not getting results. Thanks

I'm not an expert but this problem is so common and its always either the ignition switch or key cylinder. Not sure why you are resisting changing it for good measure. The boths collectively shouldn't be more than $50. If that is too much, invest in a battery shut off switch. You can get them at RV stores. That way you turn the knob on or off as you exit or enter the car. It will get old fast and make you want to find the money for the parts.



Here's some advice from other's that usually advise others:



fordtechguru:

"sounds frustrating, try this... batteries that die like you've said usually are shorted or excessive key off drain. Alternators can charge at spec. voltage but still drain or emit a/c voltage (battery killer). Grab a dvom and check for a drain. First clue it's bad is if you remove the positive cable (key off) and big blue spark. But start by trying to remove the charge lead off the back of the alternator, if the draw stops, your in luck. P.S., please don't tell me you have a 1,000 watt amp in the trunk after all this.....lol"




Old School:

Common draws of current in Mark VIIs:


BAD KEY CYLINDER IGNITION SWITCH (not ingition switch)

*interior lights
*glove box light
*under seat lights
*under dash lights
*vanity mirrors
*rear seat cortesy lights (switches down = off)


non functioning accesories

*windshield wiper motor burned out/shorted
*trunk pull down motor burned out/shorted
*windshield washer motor motor burned out/shorted
*door lock solenoids
*window motors burned out/shorted
*seat motors burned out/shorted
*exterior lights and their switches
*brake boost motor (not sure if you have this in 1986)


*AIR RIDE COMPRESSOR RUNNING (shut off the switch in the trunk, driver's side wall)
*aftermarket radios (spliced wires makes all of this moot)
*aftermarket alarm systems (spliced wires makes all of this moot)
*aftermarket HID fog lights (you get the picture)
*coins stuck in one of the three cigarette lighters (thanks NYC LSC)

 

[JoshMcMadMac]

Sounds like perhaps the VR is the culprit, but that is not certain. Try disconnecting it overnight to isolate it. If your battery is still good in the morning you have found the problem. Otherwise get a multimeter and determine what amperage is being drawn at the battery with the car off. Then start isolating connections, starting from the battery and working back, and look for the drop to be removed. Then, once isolated, we can better guide you.

 

[drummer97223]

Josh, The car is fine if I disconect the battery at night. Does this mean it is the Voltage regulator? Thanks to all.

 

[SilverFox]

Test for VR problem....pull the 4 wire plug on the VR on the passenger fender, if the drain goes away overnight - then it is the VR. I just fixed this also.

Take voltmeter that has an amp test also..unhook the + cable and test between the cable and the post - find out how many amps it is pulling. The batter could be bad, the alt diodes could be bad, the VR might be bad, the ingnition could be bad. Hook up the voltmeter/ampmeter as mentioned and start pulling stuff until you the drain goes away.

The proccess it very simple if you have a meter like I said. But I would pull the plug on the VR after you hook up the meter - bet that is the culprit.

You can also head to the Zone or Oriely's and have the system tested - if all proves good - then there is fualt in your car you need to find out. Don't chase a problem if the battery is BAD - lot of work for nothing.

These problems are very common on the M7, good luck.

 

[JoshMcMadMac]

Josh, The car is fine if I disconect the battery at night. Does this mean it is the Voltage regulator?

No. That means that you removed the battery from the circuit, so whatever is causing the drain can no longer affect the battery.