Electrical Electrical drain driving me crazy

[Mstng93SSP]

Ok, my 94 cobra is still draining the battery if it sits for more then 2 days. I hooked up a multi meter between the negative post and battery cable and see there is a draw. I pulled EVERY fuse and nothing changed. I also tried this same method with a test light and the light never went out. I also tried completely unplugging the alternator, no change. I unhooked the starter cable at the starter, no change. I completely unplugged the stereo and amps, no change. I replaced the airbag module (because it was bad), no change. I unplugged the cluster, no change. I replaced the keyless entry module because I had one, still drained. I unplugged the ccrm and no change. Electrical is not my thing so unfortunately this thing might be going to a shop that does electrical. This will be the first time any of my cars will go to a shop for anything. Kinda depressing. Any other thoughts before I farm this problem out?

 

[DAV87]

Me being more of an electrical savvy person, what shape are your "big 3" power cables in and I'm curious as to if your positive line is shorting out slighty somewhere between the battery and the alternator and wherever else your positive is ran to from the battery. I would say check your ground to engine block and ground to chassis connection as well but I doubt that would make a difference. I'm new to the whole working on cars stuff. But I understand completely how they work. Especially electrical.

Also I don't know if this would be happening while the engine is off, but I wonder if you have any arcing going on in your engine bay. You can check it by using a spray bottle set to mist and spraying consistently into the air space around the engine. I've not tried this before but have heard about it.

 

[General karthief]

The spray bottle test works for plug wires, I don't know about battery current. Have your battery checked or you could do it your self. Charge the battery overnight, then let it set unhooked testing voltage every twelve hours or so, it should stay above twelve volts for a week,

 

[jrichker]

Typically it is something draining the battery. Small things like glove box or courtesy lights are often the culprits. If you have an aftermarket stereo or alarm system, it is also suspect.

The ideal method is to disconnect the negative terminal, and connect a Digital Multimeter (DVM) between the negative terminal on the battery and the negative cable. Set the DVM on a low current scale of 2-5 amps if it doesn't auto range. Watch the current draw, and then start pulling out fuses. When you see a sudden drop in the current, that circuit is the likely culprit. Note that the computer, radio & clock will draw less than 1/10 amp to keep the settings alive.

Using the negative side prevents nasty accidents like shorting the wrench to ground while disconnecting the battery cable. Electrically, the test will work with either positive or negative battery cable.

 

[DSB88GT]

I had a similar issue. And as Stangnets favorite tool alluded to, it was my passenger side sun visor mirror light. The nub caused an indent in the cover and wouldn’t shut the light off when closed. I taped it permanetly off and no more issue.

 

[Mstng93SSP]

I did the multi meter and fuse pull, the draw was consistent no matter which fuse was pulled (I pulled them all). I don't have an aftermarket alarm, and I completely unhooked the stereo/amps with no change. I checked glove box light, it goes out, same with trunk. (If they were on the draw would have gone away when I pulled their respective fuses.)

 

[Mstng93SSP]

Battery is new. I also tried swapping it for the one in my coupe, no change.

 

[Dontknowchit]

I feel your pain. Following to see what you come up with. I have a parasitic draw on my fox I can't track down.

 

[Mstng93SSP]

I had one on my fox before. It was the alternator.

 

[General karthief]

My fox has a parasitic drain on my wallet

 

[Dontknowchit]

My fox has a parasitic drain on my wallet

This!

 

[Mustang5L5]

For this sort of troubleshooting I ended up buying a used meter on eBay. I bouht a clamp on style meter capable of reading D.C. Amperage.

It makes things easier because you can quickly clamp on various wires and measure current draw. No need to unhook wires and put in series.

I'd probably find a more useful range than the 0-40A this one has. A clamp on meter with a 0-5 or 0-10 range would be ideal

 

[88LXSleeper]

Mine was the horn foam in steering wheel keeping relay energized, PO just unplugged horns.

 

[Blown88GT]

Start looking for things that don't go through the fuse box. Remove the fuse links at the starter relay.

 

[Blown88GT]

...A clamp on meter with a 0-5 or 0-10 range would be ideal

Never saw a DC clamp meter in this range because magnetic field is too weak to measure accurately. The one you show is the first one I've seen with a 0-40A range. Same manufacturer has a model with 0-4A range.

DC clamp meters work on the principle of the Hall Effect. Hall effect sensors sense the magnetic field caused by current flow which causes a small voltage across the Hall effect sensor. That voltage, which is proportional to current is then amplified and measured.

 

[mikestang63]

start pulling fuses one at a time ..see if you continue to get voltage drop at the battery... then start pulling wires off the starter solenoid one at a time.....

 

[Mustang5L5]

Never saw a DC clamp meter in this range because magnetic field is too weak to measure accurately. The one you show is the first one I've seen with a 0-40A range. Same manufacturer has a model with 0-4A range.

I assume you mean this model?


I wonder how accurate it is at 4amp. I feel that range would be better suited for this sort of troubleshooting. I might keep my eye out for a cheap used one. The 0-40a was nice at getting some ballpark info on actual current draw of various e fans and such.

 

[Blown88GT]

I assume you mean this model?


I wonder how accurate it is at 4amp. I feel that range would be better suited for this sort of troubleshooting. I might keep my eye out for a cheap used one. The 0-40a was nice at getting some ballpark info on actual current draw of various e fans and such.

I was going to buy one of those but Amazon reviews are terrible. Many had to return them., some fell apart upon first use.

I've had this one for 15 years. It measures down to 1.0 A.
I originally bought it to test the Mark VIII fan. Win no soft start it was 105A starting, 42A running. The DCC PWM controller is 65A starting,
I just used it a few days ago to determine the parasitic loss on a Corvette. It flashed between 0.9 & 1.0.
In the past I used it on a 3000VAC motor to determine AC current draw. Didn't dare touch it while the motor was energized.
https://www.testproductsintl.com/clamp-meters-current/296-clamp-meter-amp-plus/
I use the Fluke 87-V for everything else.

 

[Mstng93SSP]

start pulling fuses one at a time ..see if you continue to get voltage drop at the battery... then start pulling wires off the starter solenoid one at a time.....

Yep, I did all that and the draw was still there.

 

[Mustang5L5]

I believe power windows draws directly from the solenoid through a circuit breaker. You might want to isolate the wires on the solenoids and do a current test on the individually and see if you find a draw on anything there.