Electrical Faults that may or may not be related. Advice sought.

[dj_efk]

Hi all,

Ever since I took over ownership, Audrey's heated rear screen and mirrors have never worked. Also from time to time, the alarm has gone off (albeit this hasn't happened for over a year).

• Re: screen and mirrors: I've checked the fuse, the light on the button lights up as it should but nothing happens (yes I have also had the mirror glasses out to check they are indeed the heated items and that they are correctly connected!). When scanned, I get a recurring code stating that the heated rear screen has an open circuit.
• Re: the alarm, scans reveal a recurrent "rear glass breakage sensor has an open circuit" fault. I have checked that the sensor is correctly connected.

My next thought was that both circuits concern the rear hatch so there is a possibility that this commonality is the key to both problems - the wiring loom to it needs to be checked for damage: I'm aware that there is no connector (the wires have to be cut to remove the rear hatch, so that rules out a bad connection there.

Has anyone either had problems with chafing wiring to the rear hatch (I've yet to examine my car closely) - or else what else could I check?

Thanks in advance.

 

[BearMcPear]

It is possible that the wires are damaged and that causes a bad connection. In fact this is relatively common on some cars where the wiring loom moves a lot when the hatch is opened.
Does anyone know if it is possible to remove the wiring loom 'tube' and check for damages that way?

 

[2work]

Morning David,

You certainly don’t need to cut the tailgate looms for removal. It’s quite a quick process to disconnect the looms from the tailgate as done this twice in a few hours a couple of weeks ago.

Have you removed the rear screen 3x trims to check that all connections are correctly seated.

Have you checked for 12v at the rear screen and each mirror when the rear screen de-mist buttons LED is illuminated.

If not then another place to check is the necessary fuse. Don't just check it for continuity but also check it for voltage. If you have 12v live each side of the fuse then the next place I would check is the connector at the rear of the climate control panel. One of the 2 wires on the 2 pin connector, from memory is the power supply out from the rear screen de-mist button. If there is no voltage coming out of the climate panel when the rear screen de-mist buttons LED is illuminated then there’s your problems right there, faulty climate control panel but highly unlikely.

Failing that if could be a broken wire anywhere along the looms length.

Having the multimeter to hand to check for continuity where you can access is the only thing you can do to determine where a possible break is.

Another place to investigate for the door mirrors, if you don’t have 12v at then is the A pillar door connectors as these can get corroded pins over time but if everything else within the drivers and passengers doors are working fine then this may not be the issue.

Having an understanding of where the power comes from and the route it travels to the 3x heated elements really does help but I beleive you already have an EWD to study. If not then let me know and I’ll explain over PM or WhatsApp. Always happy to help out, you know that.

Kind regards,

Tom

 

[2work]

It is possible that the wires are damaged and that causes a bad connection. In fact this is relatively common on some cars where the wiring loom moves a lot when the hatch is opened.
Does anyone know if it is possible to remove the wiring loom 'tube' and check for damages that way?

Morning,

The rubber weather shield/tube/grommet is removed but simply squeezing it. Give it a go and you see exactly how it comes away from the main body and the tail gate. A small squirt of silicone will assist.

Be very careful to not pull on the weather shield as you could easily damage one of the aging wires inside it.

Kind regards,

Tom

 

[2work]

Me again David,

Here’s a picture that provides the simple wiring diagram for the heated rear window:

Z1 is the heating element and connector on the rear window. The power supply comes from the climate control panels 2 pin connectors rear right. Note the wire you’re after checking if the red/black wire not the thick white wire that some people tap into for an ignition live supply.

The heated door mirror looms come from the door control unit which you’ll notice if you remove the door card. It’s the 16 pin connectors each side of the vehicle. Check the necessary pin for 12v live with a multimeter when the rear window de-mist buttons LED is illuminate/on.

This is also something I need to investigate myself but not quite a severe as your issue. My heated rear window works as it should but I don’t have 12v at either door mirror. I’m hoping it’s a simple loom issue and not corroded door connector pins. Another job for another day but quite interested in how you get on.

Although your rear window and door mirror issues could be related, they could also be totally separate problems.

Kind regards,

Tom

 

[PlasticMac]

I'd think the two faults, rear screen heater, and heated mirrors are likely to be related. For them not to be would be, imo, an unlikely coincidence.
They are both initiated by the screen heater switch. The Climatronic then powers the rear screen, and also, via the door controllers each side, which actually power the mirror element.
So, my suggestion is that the problem is in the Climatronic, possibly the switch itself.
Mac.

 

[2work]

I'd think the two faults, rear screen heater, and heated mirrors are likely to be related. For them not to be would be, imo, an unlikely coincidence.
They are both initiated by the screen heater switch. The Climatronic then powers the rear screen, and also, via the door controllers each side, which actually power the mirror element.
So, my suggestion is that the problem is in the Climatronic, possibly the switch itself.
Mac.

Agreed Mac,

Time for David @dj_efk to get the multimeter out for some testing. Having a spare climate control panel could be the simple answer if he has one to test.

Kind regards,

Tom

 

[audifan]

Make sure the relevant circuits are correctly earthed. More and more it is earth rather than power supply issues I am coming across.