For the last two years I have been pulling the negative battery cable any time I park my 1990 240 Wagon for longer than O/N (one night). There is a 4.8 amp current running all time. I went through the usual process of pulling fuses one at a time and no fuse has any effect on the current. This includes the 25 Amp FI fuse under the hood next to the positive terminal block - also no effect. That is why this has been going on for 2 years unresolved. I haven't had much time to work on the car recently.

I had to replace the alternator last weekend and while the car was up on ramps I tried another electrical experiment - disconnecting the starter. That e like one of the few things that is connected to the battery but does not run through a fuse. Again, no effect. So, I tried tracing out the two smaller wires coming off the positive terminal. One goes to the positive terminal block and the other goes to the 25 Amp fuse. I found that if I disconnected the one that goes to the Pos. term block AND pulled the 25 amp fuse the drain stops.


If that isn't strange enough, I also noticed that if I momentarily either reconnect the wire to the terminal block or momentarily slide the 25 amp fuse back in, and then disconnect either that the current drops SLOWLY from 4.8 amps. Looks like it would take about a minute or more to drop to zero. I haven't had the patience to wait and time it. ;-)

Looking at the wiring diagram online I noticed that about the only place there is a nexus involving the FI fuse circuit and anything running through the ignition switch is the fuel injection relay. I tried pulling that but it had no effect on the drain current.

Since the terminal block feeds the fuse panel and ignition switch and I now know that somehow two circuits are involved I tried going back to the fuse panel WHILE the 25 amp fuse was removed. Sure enough, if I remove fuse #8 I get the slowly dropping current. Now we're getting somewhere, but where?

Any suggestions about where 4.8 amps could be going that involves the FI circuit and circuit #8, and why that current decays slowly when the load is disconnected? This seems like a pretty good head-scratcher.

Broos

I have nothing to offer on your problem, but you should pick up a battery post switch,

Inexpensive, easy to use - no battery drain.

Can even serve as a theft deterrent.

Yup a head scratcher that's been solved before when the embarrassing discovery was made that the measurement was actually 4.8 milliamps, or that the 10A shunt's meter fuse had long ago been sacrificed.

Do me a favor and substitute a good-sized light bulb for your ammeter and re-test the parasitic drain, and I'll do you the favor of sticking with you until you solve the problem.

Here's an example of just such a test light made from the intact high-beam section of a dud headlight capsule:


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Art Benstein near Baltimore

I had no Monet to buy Degas to make the Van Gogh.

DOH! Now I feel special :-)

Sure enough, the 10 Amp fuse in the DVM was burnt.
Switching scales led to the discovery that I was really dealing with a roughly 250mA drain, more or less as you predicted. I didn't have a spare headlight bulb laying around to try as a test light.
I don't know why I never tried the mA scale on this before. Must be that I tried the Amp scale first, saw something, and just stuck with that plan.


So, rechecking things I had gone over before led to these "new" findings:
1. The 25Amp FI fuse is not involved.
2. Fuse #8 still is. If I pull the double green wire off the front of the two terminals on the side of the fuse block the drain drops to about 8-12 mA. The next double green back does not affect the drain.
3. There is still a slight slow decrease in the drain current over time.

Art, I saw your post from last year where you recommended disconnecting the 3-wire connector with the red, black, and green wires. Tried that but that did not change the draw.

Note that all of these tests were done with the drivers door open. That should mean the courtesy lamp delay is not activated. I have the knee bolster off and have tried to find that delay relay but it has eluded me so far.

I think you're headed in the right direction. The delay relay drains the battery with the doors closed when it faults. Clipped to the brake pedal frame originally, I think.




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Art Benstein near Baltimore

Birds are grouchy in the morning because their bills are over dew.

I thought that connector might be it. I have that, but it is dangling free. I guess that means the delay relay is not the problem. I wonder if that is why the dome light is so dodgy...

Anyway, I have to close this up now because I will be using the car tomorrow. I provisionally conclude that I need to go over the door lock wiring. Is that still a possibility here even though the 3-wire connector made no difference?

It was embarassing, but not a total waste of an afternoon - I reconnected the drivers side heater vent and put a radiator clamp around it for good measure while I was in there.

Thanks Art!

The slow decay symptom matches the door locks because the lock motors are protected by a PTC thermistor disc. The three-pin red/black/green connector would keep the usual cause from enabling the lock motors -- the rotten insulation on the key and knob switches in the driver's door. But, this can be very intermittent, so you might discount it during a time when it isn't happening.

#8 fuse feeds a lot of battery-hot loads; glove box, trunk, power antenna, underhood lamp. If not one of the two heavy hitters we've discussed, you may have to resort to clipping those green wires that are joined in the crimp to separate the one with the load. I recommend you find a light bulb to substitute for fuse 8 while you work on it. Won't need to be a headlight with only a couple hundred milliamps being sought. A meter can sometimes be tough to interpret when normal loads, such as clock, radio memory, ECU keep alive current become red herrings. You are looking for battery-killing loads. Even 250 mA should not drain your battery in less than a week.

So you're saying someone already removed the delay relay? Nothing like being the second one up a mystery path.

From our glove box kit:


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Art Benstein near Baltimore

To write with a broken pencil is pointless.

Only thing that makes sense is a capacitor slowly charging up to voltage. I believe the airbags have large capacitors to fire them if the battery power is cut. But they should charge up when the engine is running and slowly discharge with engine off. you really do not want to mess around with airbags and set one off in your face.
Only other thing I can think of is radio capacitors or ignition. does modern ignition still use capacitors?.
Bill D.
Modesto, CA