Weird current drain

[bmw540]

Hello all again...

I am slowly getting to the source of my electrical issues. First was a low battery issue which has been resolved by getting a new battery . Then I had a current drain issue . This was caused by the rear window blind, so removing the fuse has fixed the issue. Now I have another current drain. I now have my multimeter fixed to the dash watching the charge voltage and have noticed the voltage drop down from 13.9 to 13.0 when the engine gets hot. Is there a fan or something which turns on when the engine gets hot? as the voltage goes back to 13.9 when cold, like a ECU fan or something. I am going back to the drawing board tomorrow when I get some time to pull fuses. Hopefully the drain is there with the ignition on.

Any ideas please let me know.

[billy]

Hello all again...

I am slowly getting to the source of my electrical issues. First was a low battery issue which has been resolved by getting a new battery . Then I had a current drain issue . This was caused by the rear window blind, so removing the fuse has fixed the issue. Now I have another current drain. I now have my multimeter fixed to the dash watching the charge voltage and have noticed the voltage drop down from 13.9 to 13.0 when the engine gets hot. Is there a fan or something which turns on when the engine gets hot? as the voltage goes back to 13.9 when cold, like a ECU fan or something. I am going back to the drawing board tomorrow when I get some time to pull fuses. Hopefully the drain is there with the ignition on.

Any ideas please let me know.

firstly if you have the multimeter on the dash, where are you taking the charge feed from? unless its on some hefty wires direct from the battery you arent going to get a good read - you may already know that - just asking

also a current drain while the car is running shouldnt really be a problem as the alternator should be able to cope

[BillionPa]

there is an ECU fan, but i think i read somewhere its not thermostat controlled and runs all the time

[BillionPa]

also, a current draw that would drop the system voltage by that much would be.... massive, like a stereo amp, or some kind of electrical heater.

[bmw540]

yeah something is going on but did not get time last night to have a look as the wife is due any day and needs me to help out... so car comes second at the moment.

The meter reading on the dash is voltage not current as have been advised I will blow something up and the current will be too large to measure.

The voltage drop only happens when the car reaches operating temperture. Runs perfect when cold.

I have removed the radio fuse and no change.

On my way home tonight will pull the aux fan and see if there is any difference.

Is there a fuse for the ECU fan that I can check.

[shogun]

I only know it from my E32: the small fan for the E-box has the size of a PC fan, have my doubts that this could be the culprit.
I runs at 2 speeds. Always on, and when the temp in the e-box exceeds 44 degree C or so it switches to higher speed.
If it goes bad, it will start 'singing' like a bird.

[gmannino]

E34's all have tons of electronics to go wrong. Most of the time current draws are small electrical circuits that drain your battery everynight until the battery will not hold a charge anymore. Car audio, video, etc, most of the time, do not present current draws, but sometimes it does happen. I've fixed hundreds of current draw problems.

-Take a test light (the ones with the bulb)
-Disconnect the negative side of the battery and connect the probe between a good ground and the negative side of the battery.
-With the car not running and the ignition key out, the test light should be bright or glowing.
-Pull each fuse, ONE AT A TIME.
-When that light goes out, you have found the exact circuit the current draw exist.
-Investigate circuits individually, one at a time, to find draw.

IF you still dont find one, start pulling your fuseable links.

hope this helps

[bmw540]

only problem is that it only happens when the car gets hot so it going to be a pig to find.

[gmannino]

So how do you know you have a current draw? Does the battery die everynight? When the car's running, all electrical will draw from the alternator. The car gets hot everytime you drive it.

[PaulJ]

After the engine is hot (13 volts), what happens to the voltage when you turn the headlights on?

Paul