Battery Keeps going Flat

[harps21k]

Hi guys

Im having problems with my mercedes sprinter 311CDi.
On friday morning the van would not start and had to call the AA. The AA used a starter pack to fire up the van and said that i need a new battery as it not charging well. I then went to the petrol station to fill up and turned the van of for 30sec and it wouldnt again start. Had to then call the AA again.

On friday morning i brought a brand new heavy duty bosh battery. The van fired up perfect and ran the full day. On Sunday i went to start the van and the battery was again flat. I used my mates starter pack to fire it up. There are no lights on the dash. I used the van the full day on sunday and it didnt stop and worked well. got home and tried starting it and it did. 10 minutes later it wouldnt. I need some help as i dont know if its the alternater or what...

 

[anyweb]

sounds like the alternator all right, but could be something else,

for example, on my old 190d, i noticed the battery kept going flat and after jump starting it myself a few times i recalled that i had been doind some electrical work in the boot, sure enough, i had incorrectly wired the boot light so that it was always on, even with the boot closed, and that explained my battery drainage, once i rewired the light, my problems disappeared,

so check your alternator but also check out the other electrics in the car, maybe something is on, when you think it's off

cheers
anyweb

 

[Parrot of Doom]

Turn the headlamps on and start the engine. If the headlamps dip noticeably when the engine is running, check your alternator.

 

[Stevie A]

Check all fuses are in correct position and in proper as an arc can cause the battery to drain too.

 

[johnb80]

When you return from a days work, disconnect the battery. If it starts ok the next morning something is draining the battery i.e. light left on, alternator diodes u/s etc. This is a simple and decisive test.

Regards - J

 

[martthefart]

I had an electrical problem where the battery kept draining. Breakdown bloke advised new battery needed. Got new battery, same problem within two days. Garage suggested new aleternator as it wasn't putting the correct charge into the battery. New alternator, same problem within two days. Prior to this my usual tech said sounds like a boot light switch. I checked but couldn't find anything amiss. A week later I notoced my boot open indicator was lit. Checked the boot light switch again and a presto found the fault. The fault was intermittent so difficult to spot. The boot light draws about an amp of power so can quickly drain a battery overnight. This was an expensive lesson for me as it cost in the end nearly two hundred pounds and about two days off work. The actual switch that solved the problem cost £5.60 from main dealer and took me one minute to fit!!

Check the cheapest bits first and work you way up. Don't forget that a little bulb can drain a lot of power. If you cant find a problem, take it to a reputable auto electrician and not just a garage who will keep swapping bits 'til it's mended. An auto-electrician should know how to trace the power drain. You could do it yourself with a meter and pulling fuses until the drain stops (assuming it a drain on the circuit). However, if you don't know what you're doing, get the professionals to looks at it. Good luck.

 

[Blobcat]

A good friend of mine is the lot manager for a Chevy dealer in Ontario. They have lots of issues with car batteries draining overnight. Chevy's recommendation was to disconnect all the batteries on cars left for more than a couple of days. You can imagine the pain this causes having to move the cars regularly to clear snow in the winter.
He brought home an 06 Corvette whilst we were staying with him, next morning the battery was flat. As there are no external door locks the car wouldn't open. I opened the boot via the hidden lock and managed to open the bonnet and drivers door. I then connected the Corvettes battery to the old Pontiac I was driving. Still couldn't start the car even though all lights on. Eventually playing around with the car the display asked me to select reverese gear, once I did that the car started.
Later at the dealership on checking the manual you have to put the car into reverse when switching off to switch off all the electrics. My friend had not done this which is why it had drained the battery overnight.
It pays to read the manual, with all the electrics on cars it is all too easy to drain the battery now.
If you have a fault, connecting an Ammeter in circuit with the battery should give an indication of the current being drawn. Pls don't try and start the car with the meter in circuit though.