Frustrating 3.2l V6 Battery Drain HELP!

[Ross87]

Hi Guys,

Recently I went to turn over the motor in the morning as usual and central locking was a non starter, battery out of the boot and would you know it, dead as a doornail.

Fully charged the battery up and put back in the car, low and behold dead after 24hrs.

Realised the glove box light switch was broken and stuck on, unlikely to drain an entire battery overnight but disconnected just to diagnose and still the same issue.

Sat in the car and realised the A pillar and rear speakers were giving a low hiss even when key out of the ignition. Normally I would hear the hiss for a second or 2 after keys taken out of ignition but it would stop, not anymore.

I've disconnected the leads from the rear of the head unit (factory fitted) Battery back in and works after 24hrs but dead again after 48hrs. So something is still draining the battery. Has anyone got any ideas?

Is the car not recognising the keys are out of the ignition? Seems odd as dash lights go off and interior light switches on as normal. HELP!

 

[LEE69]

 

[LEE69]

Mine was the bluetooth box under the passenger seat and took out the gateway that lives behind the glove box

 

[NHN]

Rns-e, bt, lights etc, could be anything, needs load testing on circuits, ironically enough I'm working on a 3.2 next week with the same issue.

 

[aqibi2000]

Dead as a door nail 0V measured? Then something is SERIOUSLY wrong, possibly alternator winding short or similar since it would be a very high current draw.

For example a 100AH fully charged battery with a 4a draw will last 25 hours, normal drains such as Bluetooth and head unit is typically around 1a when the speakers aren’t delivering any sound so would not be able to drain down to 0V..

good luck with the multimeter it should be easy to find since it’s such a large draw happening over such a short time vs others who have dead batteries after 3-4 days

 

[NHN]

Iirc it's more than 1a draw on my last 8p drain fix & if bt or rns is at fault, it'll wake eachother & systems also, compounding of course.

Only 1 way forward.

 

[abmat]

Have you checked that the battery is being charged by the alternator?

 

[ch1z64]

Check the age off your battery too as i found out the 1 i had in was 10yrs old so with the dashcam set to 12hrs record it used to drain my battery , now after getting a brand new 1 and DCam on 12hrs its fine

 

[Ross87]

Dead as a door nail 0V measured? Then something is SERIOUSLY wrong, possibly alternator winding short or similar since it would be a very high current draw.

For example a 100AH fully charged battery with a 4a draw will last 25 hours, normal drains such as Bluetooth and head unit is typically around 1a when the speakers aren’t delivering any sound so would not be able to drain down to 0V..

good luck with the multimeter it should be easy to find since it’s such a large draw happening over such a short time vs others who have dead batteries after 3-4 days

Yeh not quite OV dead, can't remember what the voltage was when battery was removed, but was under 10V if I recall.

I've checked voltage of battery today prior to engine on and was reading 12.52V, with engine on was reading 14.00V and after an hour drive reading 12.90V so think I can rule out alternator issues (I hope!)

 

[Ross87]

Iirc it's more than 1a draw on my last 8p drain fix & if bt or rns is at fault, it'll wake eachother & systems also, compounding of course.

Only 1 way forward.

I'm a simpleton, can't you translate into English please? Lol

When I try and use the multimeter to measure Amps drawn the screen fades so not sure the multimeter is upto the job! though tbh it's only rated to 5A and my 10A meter is ********.

I know what the RNS is, would that still cause battery drain even if I've disconnected? And what is bt? Bluetooth? If so my car hasn't got any bluetooth connection, if it has I haven't realised for the last 5 years!

Only 1 way forward? Load testing?

 

[Ross87]

**UPDATE**

Hi Guys,

I've managed to load test the circuits and various fuses in the car and found 2 culprits.

The total Amp draw on the battery was 1.09A

F24 - Control unit for CAN data transfer (Gateway) - 0.35
Fuse 16 - Interior Lighting / Reading Lights - 0.23A

When both removed together the draw is reading around the magic 50mA number.

Can anyone tell me what the control unit for CAN data transfer is, what it does and any way to try and resolve an issue on that circuit?

Also I've checked the interior lights and can't find any suspects on the circuit, I've checked main interior light, vanity lights (sun visors), glovebox light, boot light and none of them appear to be the cause. Any ideas on a cause would be incredibly helpful.

Thanks again!

 

[aqibi2000]

**UPDATE**

Hi Guys,

I've managed to load test the circuits and various fuses in the car and found 2 culprits.

The total Amp draw on the battery was 1.09A

F24 - Control unit for CAN data transfer (Gateway) - 0.35
Fuse 16 - Interior Lighting / Reading Lights - 0.23A

When both removed together the draw is reading around the magic 50mA number.

Can anyone tell me what the control unit for CAN data transfer is, what it does and any way to try and resolve an issue on that circuit?

Also I've checked the interior lights and can't find any suspects on the circuit, I've checked main interior light, vanity lights (sun visors), glovebox light, boot light and none of them appear to be the cause. Any ideas on a cause would be incredibly helpful.

Thanks again!

CAN gateway is a common drain source, good find!

It literally is the gateway between the various CAN Bus networks in the vehicle.

 

[Ross87]

CAN gateway is a common drain source, good find!

It literally is the gateway between the various CAN Bus networks in the vehicle.

Thanks aqibi2000,

Inevitable next question, any idea of how to diagnose the cause and solve the problem?

 

[aqibi2000]

Are you waiting a full 10 minutes after locking the car and then taking the readings at the Gateway and the lights? (ensuring the doors are shut and car hood latch closed too).