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MG MGF Technical - Battery Drain Again - HELP!!!!!

Sorry to start yet another thread on this but I have searched the archives and I wonder if any of the posters actually sorted their problem. Plaese post how you did it!!!

Basically, there is a constant battery drain of 0.42 Amps (does not drop at all after 5 mins when the ECU should shut down).

I have checked the following:-
* Bonnet light is going off
* Boot light is going off
* Boot lid wiring (LHS) seems OK
* Door locks seem to be working OK
* The car will Lock & Superlock normally on the blip
* Battery earth strap making good contact (must check engine strap!)
* I have had the ECU swapped for a known good one (no change)
* I have changed the ECU relay pack (no difference)

I took the lid off the old ECU relay pack and connected it up to the wiring loom. There is one relay still energised which must be the ECU Master Relay. Breaking these contacts allows the ECU to drop out proving it is the ECU staying on permanently.

There must be one of the sensors making the ECU stay on. I pulled the connector on the engine bay sensor and the fan came on so I assume this is OK.

Anything else I can try - this is driving me nuts.

Reg
R Horne

Last time I had a problem like that, was on my old Vauxhall omega..the battery kept draining overnight and it was doing my crust in trying to find the problem...turned out that the alternator was at fault...I disconnected the alternator at night and the next morning I checked the battery and it was OK.
Changed alternator no more problem...until the head gasket failed (HGF isn't exclusive to MGF's you know!)

Bob
R Appleton

Do you have a CD autochanger? They can keep going without any external indication.
The other thing I would definitely do is check your engine earth strap(like you say) to see if the alternator is having a fair chance to charge the battery. Good luck.
C.R.B. Simeon

Just another suggestion. To eliminate everything else, try pulling the fuses one by one whilst watching your ammeter. i.e pull one out, check load. If none of these reduce the load I would think thats is more than likely your alternator or you have a wiring/bonding fault. Let us know how you get on.......
Paul

As my car is parked in a garage and not used regularly I took a pragmatic approach and fitted a battery isolator. I got it from a company with a name like Vehicle Wiring Products and it fits on the battery terminal. Two turns isolates or reconnects the battery.
Brian Highe

>I took the lid off the old ECU relay pack and connected
>it up to the wiring loom. There is one relay still
>energised which must be the ECU Master Relay. Breaking
>these contacts allows the ECU to drop out proving it is
>the ECU staying on permanently.

There was some talk about this relay sometimes becoming sticky and staying locked on. Did you remove power to it and hear it turn off, or just unplug the whole unit?
Will Munns

Sir
I had a problem when the alarm had been set and left it kept going off after checking I found even when left in the garage without the alarm being set there was excessive battery drain. I went through all the tests as you have done and could not find the problem.Which ment leaving the car (a MGF Steptronic) without the alarm being set. I then rang the MGOC techical service they suggested a new battery .Hey Presto all problem solved Alarm has since been set for 5 weeks while not being able to drive without any problems. Yuo could have battery checked to seee if you have a cell down
Best Regards

Robert Harris
Robert Harris

Thanks for all your replies and sorry for taking so long to get back to you.

Sadly I have been struggling with my 2nd HGF :-(
First one went at 43,000 and now again at 67,000. Is that bad luck or is it bad luck?? (probably more likely to be main dealer bodged the first one and didn't skim the head or something). I have just forked out £500 for disks/pads MOT etc. Should have sold it as SWMBO wanted me to do.

As for the current drain:-
I have pulled every fuse on the car and the only one that caused the drain to disappear (2nd from left under bonnet when facing windscreen) is in fact the one that feeds the ECU. Also one of the fusible links did the same but that probably has the same fuse on it.

I think that proves it is ECU related (I tried a new battery and have also put in a new ECU relay pack in case it was a sticking relay).

It is in the garage (not main dealer now I hasten to add) for the HGF and it was him who swapped the ECU to test it out. He will have another look at the drain at the same time.

Will keep you posted

Reg
R Horne

Thanks for the fuse advice car started this morning.

Let me know how you get on over the ECU.

Mac
G mac

This thread was discussed between 22/04/2007 and 01/05/2007

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