I should have stated one assumption that I made: I was thinking here of a case where the "test" after removing fuse(s) is very quick, just looking at a meter or something like that. But if the test takes a long time -- maybe an overnight -- then we're back to advantage binary-search. This is so since the time to get an answer would then depend mostly on the number of testing steps (only 7 for binary, probably many more for random) and not so much on the number of fuses we ended up needing to pull.

[edit: had not seen post #40 when posting the above. I pretty much agree with that post. But why would we need to institute a new 30-minute test period as we pull each fuse under "random" search? Seems to me, if we're already in sleep mode, we're just looking for the fuse that makes the current drop.]

 

Rev. Sam, just a thought. When I first bought my '98 XK8 the previous owner said I had to run the car at least every 3 days or the battery would go dead. While I went about repairing the little quirks our cars have I noticed the trunk lights wouldn't work. Both bulbs burner out. Replaced with new bulbs, still didn't work. The lights were staying on all the time because of a bad switch. According to this forum this is another weak spot you have to watch. Replaced switch. Had car sit for over 3 weeks while on vacation. When I came home I had no problem starting. With all the work you were doing in the trunk, while working on you fuel pump, you might have done something to switch. Jack

 

Howdy Folks:

Although I did pull the cables and brute force the PASS SIDE FB, If I would have to pinpoint a single fuse circuit drain on my 2002 again, here is my thinking:

• ENGINE COMPARTMENT FUSE BLOCK (ECFB) takes 2 rounds to pinpoint and 3 additional rounds to pinpoint the culprit fuse circuit for a total of 5 rounds.
• ENGINE MANAGEMENT FUSE BLOCK (EMFB) takes 2 rounds to pinpoint and 4 additional rounds to pinpoint the culprit fuse circuit for a total of 6 rounds.
• Either DRIVER SIDE FUSE BLOCK (DSFB) or LUGGAGE COMPARTMENT FUSE BLOCK (LCFB) takes 3 rounds to pinpoint and 4 additional rounds to pinpoint the culprit fuse circuit for a total of 7 rounds.
• PASSENGER SIDE FUSE BLOCK (PSFB) takes 2 rounds to pinpoint and 4 additional rounds to pinpoint the culprit fuse circuit for a total of 6 rounds.

Here's how step by step:

(Let's assume that the culprit is in ECFB but we do not know it.)
Disconnect the cables to ECFB and EMFB and do Round 1 (~30 minutes)
Ah ha! We have an indication that it is indeed one of these two, so we connect one cable back to either ECFB or EMFB and run Round 2.
Ah ha! We have an indication that it is indeed in the ECFB.

We are now ready to start pulling fuses for Round 3, but which ones?
Six fuses, #9,12,14,16,18,22, are the active ones that we are concerned about. The other fuses are inactive because they are controlled by the ignition key which has turned off that fuse block relay that provides current to them. (Ok, the relay contacts could be stuck causing a multiple fuse circuit problem that is beyond the scope of this single fuse circuit search)
So, since there are in effect 6 fuses, lets use the "divide and conquer method" and pull out half of the fuses, which is 3, and then run Round 3. (Always make sure the fuse block cable is connected when going through these fuse pulling routines)
Next push in or pull out (as required) half of 3 which is 2 as we will always round up to the next whole number and then do Round 4.
Lastly, push in or pull out half of 2 which is 1 and run Round 5.
Ah ha! We have an indication that it is indeed that one fuse circuit!

(Now, let's assume that the previous Round 1 and Round 2 indicated that the culprit is in EMFB but we do not know which fuse.)
The EMFB has 11 active fuse circuits. (Fuse # 1,2,3,4,5,8,9,11,15,17,18)
Again, use divide and conquer. Half of 11 is 6, so we pull 6 fuses for Round 3.
For Round 4, push in or pull out 3 fuses
For Round 5, push in or pull out 2 fuses
For Round 6, push in or pull out 1 fuse
Ah ha! We have an indication that it is indeed that one fuse circuit!

(Now, let’s assume that the previous Round 1 Indicated that neither the ECFB or EMFB had the culprit. So, having spent Round 1,we can go on to Round 2and Round 3 in similar fashion for the next pair, DSFB and LCFB, disconnecting both of their cables for Round 2 and reconnecting one cable for Round 3.

DSFB has 12 active fuses ,#1,2,3,5,6,7,8,11,13,15,17,and 18.
Pull 6 for Round 4
Push or pull 3 for Round 5
Push or pull 2 for Round 6
Push or pull 1 for Round 7
Ah ha! We have an indication that it is indeed that one fuse circuit!
Or if instead it is the LCFB, then:
LCFB has 10 active fuses ,#1,2,9,10,12,14,16,18,20,and 22.
Pull 5 for Round 4
Push or pull 3 for Round 5
Push or pull 2 for Round 6
Push or pull 1 for Round 7
Ah ha! We have an indication that it is indeed that one fuse circuit!

Finally, let’s assume that previous Round 1 of the ECFB and EMFB pair and Round 2 of the DSFB and LCFB pair indicate that none of those 4 fuse blocks has the culprit. Then by default, we know that the culprit is in the PSFB. This is the block that I would have difficulty disconnecting the cable. But,since we know the culprit is in this block, we can go ahead to this fuse pulling routine Round 3 with it connected:

PSFB has 12 active fuses ,#1,2,4,5,6,7,8, 9,11,15,17,and 18.
Pull 6 for Round 3
Push or pull 3 for Round 4
Push or pull 2 for Round 5
Push or pull 1 for Round 6
Ah ha! (note:some of my ancestors were pirates)We have an indication that it is indeed that one fuse circuit!

And so, that’s my thinking.

 

Any updates Sam?

 

Hey Pophen, Where is the switch? I have a similar issue and have not been able to find it, my trunk lights do not come on so I just assumed it was not them, but this may be my ticket.

 

UPDATE: Oops...Gus had posted about this earlier ....sorry Gus


adam699 on the XJ forum just made reference to this 'fusebox ammeter' for 15 bucks at Harbor Freight: 20 Amp Automotive Fuse Circuit Tester. Cool little device. Might be helpful here...

 

500 ma is 10 times the standard as I'm sure you know. I have had luck installing my ammeter between the battery terminal and the positive battery cable, then pulling fuses until it drops. I suggest starting with the trunk light circuit. I think this uses a microswitch in the latch and these seem more vulnerable to failure than other types of switches. The same goes for all openings, doors, glove box and so on. Things that don't work with the ignition off can be ignored. I too think that a follow up on the Autozone test is worthwhile. I bought a 1000 amp battery load tester from Harbor Freight that works fine and I trust it. Nice to be able to do this test whenever you want. The battery should measure 14.4 v across the terminals with the engine running, or the alternator may be duff.

 

scottatl, when you open the trunk look straight down. You have to remove that plastic piece. Just a couple of plastic screws hold it on. The light switch is right next to the latch. I understand this is another weak point in our cars. Jack

 

So, this is how your pirate ancestors would have found the fuse? Man, those were some smart dudes!

 

Not smart, just vocal.

 

Hi Sam I keep looking in the hope you have sorted your problem and helpful advice keeps coming your way.
Alan

 

I think I have a combination of weak battery and a drain coming from the circuit that powers the lights inside the car. If I pull the fuse to the lights (driver's side fuse box, second fuse up on the right) the current draw drops to about 200 miliamps, which is about a 60% reduction over the 500 miliamps I see with the fuse installed. Even then, however, the following morning the car is slow to crank and I then have to reprogram my windows. I bet a new battery will make the current drain unnoticeable unless I leave the car parked for a week or more. But the people at the auto parts store where the battery is under warranty say that the battery is fine, so they don't want to replace it under warranty. I might just bite the bullet and spend $200 on a new battery. Before I do that, though, I'm going to completely disconnect the battery this afternoon after it gets a full charge and then see how the car cranks tomorrow morning.

 

I think there may be something that is preventing one of your communications networks from sleeping.

Is your bluetooth reader always plugged in?

 

YES!!! I'll try unplugging it! Good idea!

 

If it is not the bluetooth, another strategy is to unplug control modules one at a time.

In some Mercedes, it is very common for the CAN bus trancievers in (usually) the seat modules to partially fail and lose their ability to go to sleep....there could be something along those lines going on here.

 

Before you reconnect your battery tomorrow put a meter across it should read at least 12.75volts after it has been charged and rested for a while.Anything less means its in poor condition.With no load on it how many days I wonder would it hold its charge?
All the best Al

 

Sam - 200 milliamps is still too much. I recall the current draw for a sleeping vehicle should be on the order of 20 milliamps.

 

Here some info on a 2000MY car:

5 Turn the ignition ON (position II); wait five seconds; turn the ignition fully OFF. Close and lock all doors.
6 Wait thirty seconds. Check that all interior lamps have 'timed out'. Record the current reading on the DVM. (Select a more sensitive range where appropriate). This reading should normally be 250 - 500 milliamps.
7 Wait for a further sixty minutes; again record the DVM reading. This reading should not exceed 40 milliamps. Where a final reading in excess of 40 milliamps is recorded, this is an indication of a spurious current drain from the battery; this must be traced and rectified.

This info comes from tsb 414-06, that discusses a faulty O2 sensor relay that could cause a drain.

 

This chart on current testing might help http://jagrepair.com/images/AutoRepa...%20Testing.pdf

 

this must be traced and rectified.

I would not like to hear these words from a service writer.