Hi all, I am having an issue with battery drain on a MK2 Focus. If left over night the battery is completely flat by morning.

I have followed the steps in this YouTube Video, hooked up my multimeter to measure the current over the battery (which is new) and pulled the fuses one by one. The current draw always remains high and alternates every second or two between 1.2 and around 3.2 amps. Does anyone have any more ideas? I thought maybe the current flicking between the two readings might be a clue to someone more knowledgeable than me! 

Looking for a parasitic current draw is not an easy thing and can take many hours, even a day or more and that's with all the gear and with good knowledge.

Firstly remember that every time you pull a fuse or open a door etc. you cause the car to go through it's wake up mode. You then have to wait for that to finish before moving on to the test.

If and it a big IF your car has the separate Bluetooth module fitted, (often mounted on the underside of the dashboard just above the glovebox) you could try unplugging it as they are quite a common cause of battery drain.  Another common cause of this problem is the instrument cluster.

You also need to get a laptop and down load FORScan and connect up to the OBDII port with a good ELM327(modified) cable from TunnelRat Electronics. You will be able to check for any DTC's and monitor the Canbus status. The problem is most likely that one of the many modules is not going to sleep. This keeps the Canbus active and in turn everything else remains in the standby state.

 

I'm also having problems with battery draining, replaced battery yesterday car was fine this morning drove for 15 miles and broke down. When key is in ignition I can hear a clicking noise coming from fuse box in passengers footwell. Used jump leads to get car started but now battery draining again.

 

Is this electrical fault or alternator (had this tested and was fine apparently).

 

Has anyone got any ideas or do I take it to garage to get full diagnostic to find the problem.

 

Jason

You need to get it looked at by an Auto-Electrician.

 

I’m not saying it is the alternator but you can try it by disconnecting alternator and leaving car for a while and see if battery drain still occurs. Years ago I had a car which leaked battery charge back through alternator when parked.  Alternator contains a rectifier which is made up from a number of diodes. A diode is like a valve that lets electricity pass in one direction but not the other. If a diode fails it lets the battery discharge slowly through the alternator windings  even though the alternator appears to charge when engine running

Thanks all for the suggestions. I'll give some of them a go and if all else fails contact an auto electrician. Is there an easy way to disconnect the alternator? I remember there is a clip on the alternator its self but is there one more easily accessible? 

An alternator can indeed cause a battery to go flat - as someone mentioned, it's the (faulty) diodes in the rectifier pack which allows the battery to discharge via the rectifier.  Back in the late eighties I had a Rover 2000 whose battery would go flat quickly - by the time a fully charged battery had been fitted and tightened, it had gone so flat that it wouldn't even put the dash lights on .. a whole minute.

The easiest way to test the alternator would be to disconnect the leads at the rear of the unit, fit a charged battery and leave it overnight. Try starting the car the next morning ..

On a 1998 4 litre Jeep I was plagued by a constantly discharging battery.  It could discharge overnight, or over two days. I was assured that it was a failing battery... and a brand new battery didn't cure the fault. It had to be the alternator - so I fitted a brand new rectifier pack to the alternator only to find that didn't make the slightest bit of difference either.

I went to an auto electrician who within 5 minutes found a parasitic drain. Repair meant stripping the dash to remove the circuit board where the fault was ... or he could fit a simple on/off switch to bypass the parasitic drain.  I chose the switch ..

I would take the bull by the horns and visit an auto electrician.  At least he will be able to identify the fault and then it's up to you what you do about it.

Good luck.