Immobiliser Battery Backup - Where is it located?

[Ade T]

So I've got a battery drain on my Clio 182, its fine if you use it everyday but leave it 2-3days and it goes flat. I tried to investigate myself but I didn't get very far. Having had enough I dropped it off at a reputable auto electricians in the hope it would be something simple and they could sort it. Anyway, I left it with them all day today and they found the drain and diagnosed it as possible an aftermarket alarm/tracker. I gave them the go ahead to remove it but after stripping it down they found it to just be the normal Renault alarm/immobiliser. They claim the fault is the Renault immobiliser battery backup that has gone and as a result it is drawing from the battery hence the flat battery.

So..

1. Does that sound plausible?

2. Where the hell is the immobiliser battery backup located? - Hopefully its something I can change myself.

 

[TheEvilGiraffe]

Check all the main earth straps.

50p says one of those is fubar'd.

 

[Ade T]

I checked the rear lights earthing points and both earths behind the N/S/F headlight and there were all fine. I didn't check the gearbox earth strap but I can't see it being that.

Probably worth mentioning I have no other symptoms just a battery drain.

Still putting your 50p on it being an earth? haha :rasp:

 

[TheEvilGiraffe]

Yes as you haven't checked the one that normally goes...

 

[Ade T]

Its something I will look at, I'd be happy if it was just that.

The car also has an RS Tuner Remap, could that be part of the issue?

 

[andy-reid]

there aint a battery back up on the immobiliser it is part of the uch/engine ecu software makeup the key is read by the reading coil around the key barrel when the ign is turned on that comunicates to uch in turn authorises the engine/starter the alarm is in the heater plenum you can disconnect the alarm behind the glove box but be aware if the backup battery hasn't failed the siren will sound for a few hours so best remove it open it up and disconnect internal battery
have they told you what amount of drain you have?when the car is at rest it should be around 0.03a but 0.05 is ok any more will eventualy drain battery
the way i would trace it is put ammeter in line and remove fuses one at a time (refit if it is not the one ) to find what is drawing power?

 

[Ade T]

Interesting.... So where is the battery backup for the alarm?

The drain I was told is 0.4amps.

 

[Sean6545]

Alternator draining battery. Dissconect it and see if the drain goes.

 

[MicKPM]

Alternator draining battery. Dissconect it and see if the drain goes.

I was going to suggest this also Sean

Ade T the Renault Cobra/Sigma fitted alarm systems have there own built in battery pack in the power sounders. It's easy and common to point the finger of blame at this but if the auto electrician has done his/her job correctly they would be able to identify the actual circuit that is pulling the excessive load and isolate it (stopping it and thus proving the fault) but 0.4Amps isn't massive to cause a flat battery over night (Unless your battery is buggered to).

Also, think of the RSTuner map as a piece of software running on a computer - If the computer isn't on the software cannot run so this is not going to be the cause of your power drain.

 

[Dr HMS Derv Destroyer]

Might sound daft, my battery was drained by a lose battery clamp, mainly the red one.

 

[Ade T]

When I did some searching around I came across a few people who noted the alternator had been a cause of the drain, in my case with it being at the auto electricians all day and they have a good reputation I would of thought they'd have picked up it being the alternator? It was my dad that took the car in for me so I've only got half a story from him but from what he's told me they said it was the immobiliser backup battery and they didn't want to mess with it as the ECU is linked into the immobiliser.

However, it would appear the only source of a battery backup is from the alarm siren? Where is this located? I have another Clio 182 I can steal this off to test.

Not sure if it makes a difference but I left the car unlocked for a couple of days to see if it still went flat without the alarm being armed and it still did.

At least the RS Tuner can be ruled out.

 

[Ade T]

I have just been up to speak to the auto electrician in person. It would appear he has done the basic checks, i.e. taken all the fuses out to see if the amp draw stops but it the drain still persists, he also ruled out the alternator.

So... if the drain isn't coming from anything on a fused circuit, what else is there to check? or what power runs on an unfused circuit?

I'm going to check the condition of the gearbox earth today to rule that out. I've checked the earths behind the headlights and rear lights all ok, is there any other earths?

 

[Sean6545]

Pulled the relays? Could be a relay sticking on.

 

[MicKPM]

Nothing runs on a direct battery/unfused circuit... to do so would be dangerous!

It could be an issue with a control/actuator relay sticking (live data and physical temp checks would help confirm or deny this) an actuator, controller or accessory issue.

Without seeing the car though it's a pretty difficult thing to properly advise on.

 

[Ade T]

Jesus, it could be anything then! I've got a spare alarm siren is that worth trying?

 

[MicKPM]

Not really as they're hard wired with no plug connections. You be better off removing the interrupts and repairing the breaks to see if it fixes the issue (personally I don't think it will)

 

[Sean6545]

There is a plug connection on the siren. Under the black piece where the wires enter. Unscrew that and you will see.

 

[Ade T]

Do you need to take the wiper linkage off to get to it?

 

[MicKPM]

It depends where the installer placed it but usually yes, it's behind the wiper linkage assembly