Hi everyone
Hope your not too busy...
Was wondering if anyone could offer some advice into a rather nasty battery killing parasitic load my car has unfortunately decided to develop.
Started on Friday evening, went to unlock car after work for commute home and it wouldn’t have it.
Used the emergency key to manually unlock and quickly decided the battery was flat, reading approx 5v! that worried me as the battery is a massive yuasa 95ah agm that’s only 6month old.
I pulled it out of the car and went to my local GSF who quickly decided it was faulty and swapped it under warranty for a new one, then returned to the car popped new one in and fired up no bother!
The next morning (yesterday) off I go to start up car and sure as shit exactly the same thing! Same battery voltage of approx 5v
Now my **** really collapsed, 2 £200 Batteries dead within 24 hours! And I’m pretty sure GSF arnt going to be so understanding this time.
So very reluctantly shelve anything else I had planned that day and set about trying to diagnose the load.
Embarrassingly im a electrician so I have a VERY basic understanding of auto Electrics but by no means am I a auto electrician!
First came basic
“have I left anything on” test....erm no.
Moving on Tested alternator with batt lead off and control plug out, diaode test with multimeter checked out ok between the alt casting and batt terminal, approx 550mv one way only...not that then!
Now came the hard bit, as I had a battery that has a useless voltage I borrowed 2 fully charged from a Friend to hook up one at a time to see if we could do a ammeter test.
Once the car had settled down a bit we measured approx 7a load with the key totally out ignition.
Pulled every fuse/relay I could find at the 3 boards and not one significantly dropped the load (down to under 1a total draw).
Bugger!
Unhooked battery and tested voltage...approx 10v
This thing is pulling some serious current!
Next step was to try and start the car to check with my diagnosis tool for any fault codes, we managed to get it going by using 2 batteries in parallel and also a jump starter thrown in for good measure.
Car fires up and runs fine, diagnostics tool only shows codes I was expecting like low voltage faults etc so all clear just fine.
No lights on dashboard to indicate fault either and alternator voltage approx 14v.
While car is running i make sure everything is switched off, lights heater, radio etc. I have a very basic clk with no bells or whistles so this is easy to confirm.
We then switch car off and unhook the battery, we then connect in series a ancient anologe ammeter from a original mini!
This shows a load of 30a!
WTF is going on!
By this time it’s been all day and now very dark so we leave the battery disconnected and call it.
I have a couple of mates that are mechanics that suggested directly unplugging the glow plug module and checking load then and also the blower motor.
I did notice my blower fan going even when I made sure the HVAC was switched off but I assumed it was a trickle mode a sit wasn’t going perticually fast.
Does anyone on this fine forum of mercedes enthusiasts have any idea or advice to offer before this enthusiast loses his enthusiasm?
Thanks in advance!
Hope your not too busy...
Was wondering if anyone could offer some advice into a rather nasty battery killing parasitic load my car has unfortunately decided to develop.
Started on Friday evening, went to unlock car after work for commute home and it wouldn’t have it.
Used the emergency key to manually unlock and quickly decided the battery was flat, reading approx 5v! that worried me as the battery is a massive yuasa 95ah agm that’s only 6month old.
I pulled it out of the car and went to my local GSF who quickly decided it was faulty and swapped it under warranty for a new one, then returned to the car popped new one in and fired up no bother!
The next morning (yesterday) off I go to start up car and sure as shit exactly the same thing! Same battery voltage of approx 5v
Now my **** really collapsed, 2 £200 Batteries dead within 24 hours! And I’m pretty sure GSF arnt going to be so understanding this time.
So very reluctantly shelve anything else I had planned that day and set about trying to diagnose the load.
Embarrassingly im a electrician so I have a VERY basic understanding of auto Electrics but by no means am I a auto electrician!
First came basic
“have I left anything on” test....erm no.
Moving on Tested alternator with batt lead off and control plug out, diaode test with multimeter checked out ok between the alt casting and batt terminal, approx 550mv one way only...not that then!
Now came the hard bit, as I had a battery that has a useless voltage I borrowed 2 fully charged from a Friend to hook up one at a time to see if we could do a ammeter test.
Once the car had settled down a bit we measured approx 7a load with the key totally out ignition.
Pulled every fuse/relay I could find at the 3 boards and not one significantly dropped the load (down to under 1a total draw).
Bugger!
Unhooked battery and tested voltage...approx 10v
This thing is pulling some serious current!
Next step was to try and start the car to check with my diagnosis tool for any fault codes, we managed to get it going by using 2 batteries in parallel and also a jump starter thrown in for good measure.
Car fires up and runs fine, diagnostics tool only shows codes I was expecting like low voltage faults etc so all clear just fine.
No lights on dashboard to indicate fault either and alternator voltage approx 14v.
While car is running i make sure everything is switched off, lights heater, radio etc. I have a very basic clk with no bells or whistles so this is easy to confirm.
We then switch car off and unhook the battery, we then connect in series a ancient anologe ammeter from a original mini!
This shows a load of 30a!
WTF is going on!
By this time it’s been all day and now very dark so we leave the battery disconnected and call it.
I have a couple of mates that are mechanics that suggested directly unplugging the glow plug module and checking load then and also the blower motor.
I did notice my blower fan going even when I made sure the HVAC was switched off but I assumed it was a trickle mode a sit wasn’t going perticually fast.
Does anyone on this fine forum of mercedes enthusiasts have any idea or advice to offer before this enthusiast loses his enthusiasm?
Thanks in advance!