Hello all,

So, my battery is draining with the car switched off (2001 Mk2 1.2 8v). It struggles to start after a few hours and is pretty dead if left for a day. I got my trusty multimeter out and found that it was draining 650mA with everything off which I think is quite a lot. With the meter connected I started pulling fuses out one by one and one fuse F18 caused the current to fall to almost zero so this must be the culprit. The fuse is for Engine Management Control Unit but I'm not sure where to go from here.

I read the other threads on batteries draining but couldn't get to the bottom of this. I'm pretty sure I don't have a problem with the battery or alternator as I measured 12.5v across the battery with engine off and 14v with engine on. If I disconnect the battery for a few days it holds its charge. I have the original head unit and it's not the boot light (usual suspects).

This problem seemed to start after I got the head gasket changed at a garage. Does anyone have any suggestions as to what I should do next to diagnose/fix this problem.

Chris.

650mah is way to high yes

i think its 80ma drain is aceptable

dont just assume - remove the headunit over night

Have you got tow bar electronics?

Failing that - the ECU Could be still staying switched on, instead of shutting down when engine is off
Could relay its power supply but thats the extreme! idearly need to find out whats really draining the battery

Speaking of which - disconnect the alternator wires overnight if you can
Make sure they DONT TOUCH ANYTHING - ie insulate them very very well

IF the car drives fine the next day, its the voltage regulator in the alternator thats duff

Ziggy

When you tested it with a meter how long did you leave it after switching off the ignition? I'm not sure on the exact time but most ECU's can take around 10 minutes to shut down and stop drawing power.
Have you tries leaving it with the battery disconnected overnight to see if it still goes flat?
Mick

Yes they have Mick, it didn't drain when disconnected.

Ok, you need to test each circuit to find the culprit by using the amp setting on the meter. Have a look at this site for good advice at how to go about it.

http://www.popularmechanics.com/cars/how-to/repair/how-to-stop-car-battery-drains

Thanks for the responses. I have tested the current flow with the amp setting on the meter and pulled out every fuse in turn in both fuse boxes to find out which part of the car is pulling current. The only fuse that makes a significant difference is the one for Engine Management Control Unit (fuse18). When I pull the others including for the stereo or subwoofer or tow bar electrics etc there is either no drop in current or only around 10mA but when I pull fuse 18 it drops from 650mA to 10mA. Also I tried leaving the car for an hour after switching off with the meter connected but the current drain is still at 650mA so it's not just that ECU hasn't turned off yet.

Should I start pulling connectors from the ECU to narrow it down further and look for bent pins or things not plugged in tightly? This might be my next step.

I stand to be corrected by another forum member but isn't the ecu's power supply controlled by an outside relay in one of the fuse boxes? If so and that relay is sticking closed or has permanently stuck in the closed position it would explain the power draining. Have a look on google for ecu relay on fiats, never know your luck. Unless another member posts here to tell you.

i'd still be checking the alternator as well
its only 1 nut to disconnect the alternator main power cable
As said - insulate well to ensure it doesn't short on bodywork

If the draw is still exccessive, then its not alternator

Ziggy

in a good quality 200+ Ah Car battery a 650mA current draw should still take in excess of 2 weeks to kill your battery, so i suspect your problem is else where, either you have something switching on over night like a dodgy radio, a dodgy battery earth can cause an increase in power drain or you just have a very weak battery, my money is on number 3

I will go and get the battery tested however a 650mA drain seems a lot. I've heard it should be less than 60mA.

One thing I have noticed is that after I turn the engine off one of the relays in the engine fuse box makes a lot of clicking noises like it is switching on and of quickly. It sounds like it's crackling. This continues on and off for about ten minutes then gradually dies down. Is this normal? It is the middle relay of the group of three on the right of the fuse box. If anyone is bored and doesn't mind checking on their punto to see if it's a normal thing then this would really help me out.

Many thanks!

Ah! An over excited relay. You need to identify what that relay controls or perhaps more importantly if its controlled by the ecu. Best way to locate it is to get the clicking noise going and touch the top of each relay. You will feel it click. Only one relay (excluding interior lights when you open the door) works after the ignition switches off and thats the ecu for a short time only though. It should switch off after a few seconds. I would say its that one.