1999 S70NA Evita Current drain evaluation and fault testing

[abscate]

Symptom - car drained an old battery on a two week sit at college. I will get a new battery and test.

My Fluke $6000 VOM was on the fritz for some reason - I wasn't getting a reliable amperage reading, so I broke out the old Micronta

First, I played dead on road with no VOM and tried to troubleshoot with no instruments. I was a getting a thin blue spark on touching the negative to the battery post, indicative of 100s mA leakage - too much. I want to be under 50 mA (0.050 Amp)

First step - removed feed wire from positive battery post - no spark at negative - that means the alternator and diodes seem to be ok.

I went through the entire 11C fusebox (under the flip lid) trying to judge small spark (ok) from big spark but was unable to tell which circuit was pulling current.

I moved back to the big Butt Fuses feeding the Bus and found pulling number 6 cured all ills.

This feeds 5 buss circuits on the 11C, and I found #7 I could then tell big from small current drain. Said circuit feeds radio and a few other things. Pulling #7 makes drain current go from 200 mA to under 5mA

Current math - 200 mA draw will pull about 5 Amp hours per day from battery, or half battery charge in warm weather in one week.

When Abby comes home for long break, I will have a look at wiring and try to sort out - until then she will pull #6 when she parks.

Pictures to come.

[RickHaleParker]

My Fluke $6000 VOM was on the fritz for some reason - I wasn't getting a reliable amperage reading,

Semi-melted fuse or intermittent open fuse ...?

[abscate]

My Fluke $6000 VOM was on the fritz for some reason - I wasn't getting a reliable amperage reading,

Semi-melted fuse or intermittent open fuse ...?

I think it’s more serious. I’m getting about 200 mA reading with the leads grounded. Bad battery perhaps, but it’s under warranty at least.

On a bright note, Juniorette had a good head for electrical troubleshooting and was able to figure out how to track down a current leak and what order to pull fuses.

[RickHaleParker]

I think it’s more serious. I’m getting about 200 mA reading with the leads grounded. Bad battery perhaps, but it’s under warranty at least.

You sure it is 200 mA not 200uA or 200 pA? A little internal leakage is expected but not 200 mA.

[abscate]

I gotta hand it to my almost 40 year old Radio Shack Micronta VOM, workingout of box, and the analog meter was great for catching the dynamics of the current drain.

Each time you connect the battery, a couple of controllers reboot so current jumps, then drops and stabilizes. Much easier to diagnose on an analog meter.

You also never need a battery on an analog current meter

[abscate]

Oh... and by the way, this circuit also powers the d****** dome light and lock controller module that has been poking us in the eye for a year.

Hmmmmmm

[abscate]

And this was found to be a faulty passenger door switch lock button stuck closed.

Once resolved, drain current measures at 45 mA. Probably still some stuff active at that point

[wizechatmgr]

And this was found to be a faulty passenger door switch lock button stuck closed.

Once resolved, drain current measures at 45 mA. Probably still some stuff active at that point

Unplug your radio. Bet at least half of it is the memory refresh power. Betting other half is ECU/ECM memory refresh.

[850 LPT]

And this was found to be a faulty passenger door switch lock button stuck closed.

Once resolved, drain current measures at 45 mA. Probably still some stuff active at that point

I am glad you figured this out.
Since I have the exact same symptoms with my S70 I am hoping that the cause is the same.

Dirk

[abscate]

Well, it solved it for 5 days , then came back