C5 x7 tourer - fob intermittent

[Agour]

Hi all!

The fob on my 2008 x7 is a bit intermittent.

Sometimes it works, sometimes not. Its about 50/50.

Batteries are fine, and the second fob has same issue..

Any ideas on what I can check/do?

Thanks!

[GiveMeABreak]

How old is the car battery? Anything 5 years or over and will likely need changing as a weak battery causing low voltage can affect the vehicle systems.

If the battery is in good health and tested, try resynchronising the fobs. Put the key in and turn to accessory position, and hold lock button on the fob for a few seconds, turn off ignition and remove key.

Repeat for second fob.

[Agour]

Thanks for the reply

Unsure of age of battery, seems like I've never replaced it, and I've had the car since 2018.

Voltage wise it was reading 12.3v, which seems a tad low. I think it should be 12.6?

Tried the sync thing and that hasn't helped at all either.

Best bet to replace the battery then, or is there anything else I can try?

[Hell Razor5543]

I think a good battery has 13.6 volts when fully charged, while it is typically charged at 14.4 volts.

[Agour]

I think a good battery has 13.6 volts when fully charged, while it is typically charged at 14.4 volts.

I double checked and its 12.6

You're right that it charges at 14.4 though

[Agour]

I put a new battery in. After driving it, the battery read 12.6v. After leaving it sat for half an hour, the battery has dropped to 12.4

(It was 12.6 when I put the battery in, and I have only done short journeys so far).

However - the fob is still not working!

I also checked the voltage on the old battery out of curiosity - and it's now at 12.7v after being sat idle out of the car.

Could it be that something is draining the car battery down to 12.3v - which is then making the alarm not work? I checked and when locked, there is a draw of 2.4 A on the battery.

That was with 1 turn on the key in the doors not 2, so I believe the alarm shouldn't be active.

(I'm also unsure how the old battery has gone back up to 12.7v, it never read higher than 12.3v before).

I haven't changed anything on my car electrics wise in a long time. There's an aftermarket parking sensors installed, and a dashcam hardwired. However the dashcam only turns on with the ignition as it's wired into a fuse that only comes on with ignition.

Any ideas what I can check/do?

Thanks!

[wheeler]

How long did you leave it for when checking the current draw? it can take anything up to 5 minutes for everything to power down & get a correct reading. You shouldn't get more than 0.06 amps.
If your car had a 2.4 amp drain i would imagine if the car was left for any more than a day you wouldn't even be able to start the car.

[Agour]

That's a fair point, it was almost straight away.

Anyway it can't be the battery, as new one hasn't fixed the issue.

Today it worked to lock, literally 2 minutes later it wouldn't work anymore. Car hadn't moved at all, not even doors opening/closing.

Don't suppose anyone has a wiring diagram with location of the fob reciever in the car?

[wheeler]

The remote receiver is an integral part of the coms unit behind the steering wheel which is also your indicator lighting stalks. It’s unlikely there is an issue with the wiring to this as you would also have issues with your lights & wipers.

[Agour]

That makes sense!

I'm at a loss then for what else I could check. Any ideas?

[jscadden]

I have a similar problem on my C8 and the probable cause is quite unusual.

I have a dashcam that is permanently wired in. It does contain circuitry to ensure that it switches off should the battery voltage drop below a preset level.

However, I have noticed that if the camera does not automatically switch off when I park at night, the fobs will not unlock the doors and I have to unlock with a key then de-activate the alarm from the fob otherwise the alarm goes off! If I switch off the camera when parking up at night, there is no problem!

Could be that you have something constantly running which is putting a small drain on the battery while parked.