Electrical drain.

[Blamecanada999]

OK, yet another problem with the G50. It seems I've developed a power drain. I know this because of an expirement I tried last night. I checked the battery last night to make sure it was fully charged. Went out this morning to find it nearly depleted, and the car wouldn't start. I can't find any lights or other electronics that may be draining the battery. My question is this:

Is there a quasi-easy way to find the source of the drain? I know in the automotive world, the words "Easy" and "Electrical Problem" are like oil and water. I'm just sick of having to charge the battery every morning and carrying a jump pack around in the trunk. The alternator's a bit weak, bit that would have nothing to do with a drain while the car is sitting overnight. Anyways, thanks for the help.

[maxnix]

If the alternator is "weak", it may be because of a dead or dying battery.

Have you load tested the alternator? How new is the battery? Does it meet minimum OEM specifications?

[elwesso]

best way to do it is to put an amp meter on the battery... should be pretty low. Then pull out each fuse individually and that will help narrow the source of the drain.

Theres more details to what the parasitic drain should be, i cant remmeber off hand but its very low (less than 1 amp for sure, probably like .02 amps).

[qsiguy]

First of all it could just be a bad battery that is draining itself. Also, alternators can drain the battery if they are defective. Once you have both of those tested and ruled out you can check the other circuits.

You can isolate an amperage drain relatively easy. You need a good ammeter and most decent ones will handle 10 amps. First thing to check is the amp draw right at the battery. Remove your positive terminal and place your ammeter inline with the B+ cable and the B+ on the battery so all current your car is drawing is going through the ammeter. DISCLAIMER: DO NOT ATTEMPT TO START THE CAR WHILE WIRED LIKE THIS OR YOU WILL FRY YOUR AMMETER OR AT LEAST BLOW IT'S FUSE! You should see something under about ~.05 amps if all is well. Make sure the interior lights are off (doors closed), trunk closed, and the hood light disconnected to get your baseline reading. If you are seeing .5-1 amps or more you have a draw somewhere that can kill your battery. If it is draining from fully charged to dead in the morning you probably have a drain of several amps (assuming your battery is good and not the problem). You can get an idea of what some circuits draw by turning some things on, one at a time. For instance, opening your door and turning on your interior lights should show a few amps draw, headlights on should show up around 10 amps, etc. Since your battery is draining when your key is off start by trying to find the circuits that have power then the key is off. One at a time you can pull fuses to circuits that are powered when the key is off and note the amp draw. If no change reinstall the fuse and try another. Keep doing this until you find a circuit that changes your amperage draw at the battery. Since you will have to open your door to pull fuses you might want to start with the dome/interior light fuse and see if that takes care of it. If not just leave it out while you try the other fuses so you don't have to keep waiting for the dome light to shut off when you close the door after pulling out another fuse to check your new amp draw.

There are also many fuses next to the battery that you might want to start with since they are close. Also, you can pull the large fuses and remove power to the entire interior. Keep trying various fuses until you find it. Don't forget the two Black/white wires plugged into the B+ cable. Your goal is to find a starting point and follow it back to the source. I don't have my ammeter with me right now or I'd get some baseline #'s for you. Maybe I'll do it later when I get home.
Modified by qsiguy at 4:01 PM 4/2/2008

[goody90q45]

Great writeup! Since I know nothing about electrical troubleshooting I'm saving this one.

[Blamecanada999]

Wow, lots of helpful info here. Thanks a lot. The battery is only 4 months old and has been tested. Everything checked out fine there. Since I know the alternator is getting weak, I may just buy a new one anyways. After that I'll have to go through the process that qsiguy and Wes suggested.

[qsiguy]

OK, I have some baseline numbers from my '94 that's currently great in the electrical department. I pulled the negative terminal and installed my Fluke ammeter inline. Leads in the 10 amp terminals on the meter. You could use the positive as well, would make no difference. I just used the negative as it doesn't have all the other wires connected to it. Negative meter lead to B- and the meter positive lead to the negative battery cable. If you get these backwards you will just read negative amps, no big deal.

Upon connection the dome turned on and stayed on due to my aftermarket alarm until I armed and disarmed it. Then it turned off. Also, there are apparently some systems that operate for a couple minutes upon connection of power as the amps take about 1-2 minutes to stabilize at the low level.

Initial connection w/alarm disarmed, dome light on -> 3 amps, settled to 2.6 amps

Aftermarket alarm armed, dome light off -> .24 amps then settled to .066 amps after approx. 1 minute.

Alarm disarmed, dome light off -> .063 amps after 1 minute

Start pulling large fuses in under hood fuse compartment, unless noted I reinstalled the fuses prior to pulling the next fuse/relay"IGN SW" 30A fuse -> .056 amps"ENG CONT" 25A fuse -> no change"INJ" 25A fuse -> no change"COND FAN" 30A fuse -> no change"MAIN" 75A fuse -> .043 amps"MAIN" and "IGN SW" -> .035 amps*When "MAIN" reinstalled amps were at .5 amps 2 minutes then settled back to .063 indicating that a circuit was operating for a couple minutes upon power up, ECU?"Power window" fuse -> no change"Anti Skid" fuse -> no change"Blower Motor" -> no change

Small underhood fuses"Eng Cont" 10A fuse -> no change"Fog Lamp" 15A fuse -> no change"Room Lamp" 10A fuse -> no change (unless the dome light was on already)"Tail Lamp" 10A fuse -> no change"ALT (S)" 10A fuse -> no change"Hazard" 10A fuse -> no change"Horn" 15A fuse -> no change"Headlamp LH" fuse -> no change"Headlamp RH" fuse -> no change

Relays underhood in junction box (same box as above)"Anti Theft" -> no change"Cond Fan" -> no change"Cruise Cont" -> no change"Inhibit" -> no change"A/C" -> no change

MiscellaneousTrunk open w/trunk lamp on -> .4 amps (amps fluctuating +/-)Room lamp fuse out, door open -> .233 amps (might be alarm LED drawing)Room lamp fuse out, door open, park lights on -> 6.2 ampsHeadlights on -> Exceeded 10 amps, couldn't get accurate reading

This should give you a good start on tracing the amp draw. I didn't pull the two really large fuses next to the fuse/relay box (100A+) or the two black/white wires plugged in at the B+ terminal.

[Q45tech]

Since I know the alternator is getting weak,

How is the alternator defective? Loss of a phase [1-3 diodes blown open?] or the regulator has failed or a brush has worn out or the cummutator has high resistance shorts?

When a diode shorts there can be a high reverse flow back thru alternator from battery...........when regulator short there can be a few amp reverse flow.

Which is it?

Disconnect the alternator from [2 circuits] and see if it goes away.

As to trouble shooting a short [small current flow] you can either spend a few hours [take detailed readings and written notes] or have someone else do it and add an hour or 2 charges for processing your car in and out of shop.

[Skibane]

Aftermarket alarm armed, dome light off -> .24 amps then settled to .066 amps after approx. 1 minute.

Alarm disarmed, dome light off -> .063 amps after 1 minute

That's more like it...

0.3 amps of continuous drain would discharge the battery in a matter of days, rather than weeks...

[qsiguy]

Yes, my initial guestimate had the decimal in the wrong place. After I tested it I remembered that was where I would typically read the amps on a good electrical system.

Found this handy little item at Jaycar. It's an ammeter that plugs into a standard blade fuse slot to check or current draw. Pretty cool gizmo although it would be simple to make an adapter that connects to your multimeters leads and plugs into a fuse slot.

http://www.jaycar.com.au/produ...D=619

[Blamecanada999]

Since I know the alternator is getting weak,

How is the alternator defective? Loss of a phase [1-3 diodes blown open?] or the regulator has failed or a brush has worn out or the cummutator has high resistance shorts?

When a diode shorts there can be a high reverse flow back thru alternator from battery...........when regulator short there can be a few amp reverse flow.

Which is it?

Disconnect the alternator from [2 circuits] and see if it goes away.

As to trouble shooting a short [small current flow] you can either spend a few hours [take detailed readings and written notes] or have someone else do it and add an hour or 2 charges for processing your car in and out of shop.

I haven't realy taken a detailed look into the alternator, but I had a local tech take a reading and it was only putting out about 2.4 amps.

[qsiguy]

Hmm, Did he put a load on it or just read amperage while the car was running? The alternator only puts out the amps that are required. Unless he put a load on it that might have been all that the car was asking for.

[Q45tech]

When you add fuel pump, injectors, ignition, ecu, tcu, transmission solenoids, dash lights and mandantory ecu ABS, FPCU, body control etc you will see the alternator better be supplying 10+ amperes for the car to just idle in Park................infact it should have a 34 ampere capacity at idle.

[Blamecanada999]

He read both the idle output and output at a steady 3,000 RPM.

[qsiguy]

I have a clamp type ammeter, I'll check the amps running with various accessories on as well.

[Blamecanada999]

Well, I finally got around to rooting out the problem. I've isolated the source, and it seems to be located in the stop lamp circuit. The problem I'm having now is finding the stop lamp switch for the brake pedal in the FSM CD I have. Any ideas?