Focus High Parasitic Drain

I understand there are some further fuses behind the main fuse panel.

Everything off draw should be no higher than 50ma for that car (according to a site I read it on, but it sounds right)

Two things spring to mind -firstly the Central Timer Unit refusing to sleep. This is a common (ish) problem on Foci. They are about £30. Unplugging it will confirm the mA draw or not. Replacement is simple.

Secondly, and alot less common if the car is fitted with a tracker unit - perhaps unlikely on a Focus- but when the internal battery dies the charger starts drawing more power from the car. It will be wired usually to the interior light or similar circuit, which on a Focus is fed from the CTU.

Tim. .

Nor do your maths'. I make it (assuming a 38AH battery - probably more) that 200mA would take 27 days to drain a battery.

I make it 8 days for 38AH. A drain of 200mA for 5 hours is 1AH, 38 x 5 is 190 hours which is 7.9166666 days.

Have I done something stupid?

[...]

Nope; my calculations concur.

Of course, the battery would be too flat to crank the car long before it was completely flat.

Chris

As rp has pointed out, there seems to be a flaw in yours maths somewhere...

However, it doesn't work exactly like that; the Ah capacity is only accurate at a defined rate of charge/discharge. That is usually 10A for a car battery. The capacity at significantly higher or lower rates of charge or discharge will be different.

Also, what's to say that the battery is fully charged when the car is parked? A half-charged battery will still start a car, but clearly won't withstand the loss for as long.

200mA is too high for a Focus; Mr C has it spot on at 50mA.

Some VW's have a higher drain by design, and will often end up needing a jump start after two weeks.

Chris

Thanks Mr C. I'll have a look for hidden fuses, although I don't remember seeing any last time I was in there changing the pollen filter (which requires the fuse box to be moved thanks to Ford's maintenance-friendly design).

Thanks Tim, I'll certainly give that a try. Certain things like the dash display turn off as normal after 10 minutes, but the last 200mA never seems to time off, unless I just need to wait longer!

Stu

I didn't find the central timer, but according to the HBOL this model has something similar called the GEM (Generic Electronic Module) and it's built into the fusebox PCB. I did confirm that unplugging the fusebox eliminates all the load, so there are certainly circuits fed through there that you can't isolate by simply pulling one of the fuses.

Anyway, I exercised some patience and carried out a more thorough load test today. Result is there's nothing wrong with it, but it takes about

40-45min for everything to turn off! Here's the breakdown:-

680mA immediately after locking up

280mA after about 5min (Radio display goes out) 200mA after 10-15 min (Odometer backlight goes out) 90mA after about 30min (no apparent change) 10mA after 40-45min (odometer display goes blank)

So there was no need to worry, but at least I have the peace of mind of knowing that the car won't destroy it's new battery. Still disappointed with less than 7 years out of the OE motorcraft.

Thanks very much for your suggestions & advice.

Nah, it's plug-in on the back of the fuse box carrier. About 20pins.

Tim..

Buggered if I can see it Tim. I had the whole box out and there's multiplugs on both sides, but only two small relays, both of which are on the main side where all the fuses plug in. The rest of the relays are under the bonnet. Are we both talking about the same model (Mk2)?