Hello,

I'm new to Briskoda. My 2016 Fabia Mk3 heated rear window has stopped working. I've deduced that the battery is okay, the dashboard switch works and I can hear the relay operate in the Body Control Module. I have inspected the heater 'wires' in the rear windscreen and all looks okay. Resistance check gave me a reasonable reading of a few ohms. However, voltage reading at the heater was 0V.

Hoping that someone has some ideas of where I should go from here.

I'm wondering if something else might have failed in the BCM or a problem with wiring between the BCM and heater itself, or loose connector.

I've attached an image of the heated rear window circuit.

Thanks.

Have you checked fuse #41?

Yes, fuse 41 is okay. 

Is the wiring between J519 and the HRW OK?

That I don’t know as yet. Is it a direct connection between the J519 BCM connector to the HRW ?

 Once I’ve done this measurement I’ll post an update. 
(Thanks for replies so far)

Look at the diagram, there's a 10-way connector "on left in luggage compartment".

 

I've been able to do some measurements this weekend and confident the wiring from the BCM to the rear window heater is sound.

I did remove the fuse and with the heater operating (relay clicked on), measure from the BCM side of the fuse connection to the heater 'wires'.

The resistance through the circuit was high (100s Kohms). I was expecting near zero ohms i.e. a direct connection through the BCM relay. Without seeing a schematic of the BCM can't really discern what's going on from this. 

As the car is in daily use not going to remove the BCM to take a look inside. So, conceded it'll be a phone call to local Skoda garage and discuss the problem with them.

2 hours ago, spig212 said:

The resistance through the circuit was high (100s Kohms).

Between which two points exactly?

 

Remember the BCM isn't just a straight through connection - the input will go into a microchip and the output come from a microchip, so the BCM resistance will be very high.

Edited 21 January, 20242 yr by PetrolDave

Thanks PetrolDave. Please see diagram attached.

The measurement is shown by the bold blue arrow. 

I've shown on the diagram how I imagined the circuit. See the relay within the J519 part of the diagram. I wondered if the HRW dashboard switch sends a ground signal to the BCM which uses this to energise the relay. I imagined that the electrical path for the power to the HRW would only be via the relay contact since its high current.

22 hours ago, spig212 said:

See the relay within the J519 part of the diagram.

There is a LOT more than just a relay within J519, so the measurement you made is based on an incorrect assumption.

I'm not sure if this is the right place to post my comment, I am new to briskoda!  My heated rear window has stopped working as well.  I thought it might be the fuse #41 but there isn't a fuse 41!  Does anyone have any suggestions of which other fuse might be connected to the heated rear window on a 2016 Skoda Fabia?

Hi, welcome.

 

It's show as fuse 41 for my wife's 2015 Mk3, perhaps you could try a search on the 'Skoda Fabia Mk III (2014-2021)' forum (and/or ask there). - https://www.briskoda.net/forums/forum/298-skoda-fabia-mk-iii-2014-2021/

 

@Vanessa Fit a fuse in position 41 and see if it starts working again?

30 Amp is the correct rating

 

 @spig212 just because you can hear the relay operate doesn't mean that it is conducting. The contacts may be burnt out.

Where abouts exactly is the relay for the rear window heater /defrost, location please 

It will be soldered onto the circuit board of the BCM, I expect.

On 27/01/2024 at 12:01, Vanessa said:

I'm not sure if this is the right place to post my comment, I am new to briskoda!  My heated rear window has stopped working as well.  I thought it might be the fuse #41 but there isn't a fuse 41!  Does anyone have any suggestions of which other fuse might be connected to the heated rear window on a 2016 Skoda Fabia?

@Vanessa ive tracked down my fault. This post will be helpful to you

https://www.briskoda.net/forums/topic/534290-rear-demister-and-both-licence-plate-lights-stopped-working/#comment-5961198