Rear heated screen not working (mirrors fine)

Rossi1001 · Post by **Rossi1001** » Sun Apr 28, 2024 2:32 am

As above really! Enuff_zed (who is helping me, a lot!) mentioned in my project thread (link here) that the fuses are good and the connections are firmly fitted to the screen. What would be the next logical step to diagnosing where the problem is? Any tips would be much appreciated!

Sidewaze Samm · Post by **Sidewaze Samm** » Sun Apr 28, 2024 8:35 pm

Had this problem in my lad's zed - about five years ago, so can't remember the details... but IIRC there's two relays on the back of the fuseboard that are relevant. For some reason one of these was missing from his - a few quid for a new one from BMW and it's worked fine ever since.

enuff_zed · Post by **enuff_zed** » Sun Apr 28, 2024 8:43 pm

Sidewaze Samm wrote: ↑Sun Apr 28, 2024 8:35 pm Had this problem in my lad's zed - about five years ago, so can't remember the details... but IIRC there's two relays on the back of the fuseboard that are relevant. For some reason one of these was missing from his - a few quid for a new one from BMW and it's worked fine ever since.

I have a spare fusebox. What worries me is that one of the relays is inside it!

Sidewaze Samm · Post by **Sidewaze Samm** » Mon Apr 29, 2024 6:02 pm

enuff_zed wrote: ↑Sun Apr 28, 2024 8:43 pm What worries me is that one of the relays is inside it!

Not sure what you mean by inside, Martin. I think these relays were on the back - remove glovebox, release fuseboard and carefully (ie not shorting out on the car) turn it over to get access to the back.

colb · Post by **colb** » Tue Apr 30, 2024 6:40 pm

https://www.youtube.com/watch?app=desktop&v=zQuGKq5jT4A
Fuse and Relay locations
Defogger rear screen is Fuse 25 5Amp
Relays for defogger is Relay R13 and R99 both on the rear of the Fuse Board
Diagram and list here https://fusecheck.com/bmw/bmw-z4-e85e86 ... se-diagram

Rockhopper · Post by **Rockhopper** » Tue Apr 30, 2024 6:55 pm

I guess you’ve checked that it’s not in transport mode?

enuff_zed · Post by **enuff_zed** » Tue Apr 30, 2024 7:02 pm

colb wrote: ↑Tue Apr 30, 2024 6:40 pm https://www.youtube.com/watch?app=desktop&v=zQuGKq5jT4A
Fuse and Relay locations
Defogger rear screen is Fuse 25 5Amp
Relays for defogger is Relay R13 and R99 both on the rear of the Fuse Board
Diagram and list here https://fusecheck.com/bmw/bmw-z4-e85e86 ... se-diagram

Newtis shows one on the back and the other buried inside.
2 fuses, 20 & 25, both checked.
Relays K13 and K99

: Screenshot 2024-04-30 190406.png (176.82 KiB) Viewed 141 times

bigwinn · Post by **bigwinn** » Tue Apr 30, 2024 7:08 pm

Chaps-

Steve locally has the exact same issue- which we have been chasing for ages including changing all the removable relays to no avail

We are now thinking it’s the relay on the flip side of the fuse board- see pics

Anyone done this yet? I think it’s the tyco relay…

: IMG_9761.png (302.04 KiB) Viewed 139 times

: IMG_9760.png (709.76 KiB) Viewed 139 times

enuff_zed · Post by **enuff_zed** » Tue Apr 30, 2024 7:29 pm

bigwinn wrote: ↑Tue Apr 30, 2024 7:08 pm Chaps-

Steve locally has the exact same issue- which we have been chasing for ages including changing all the removable relays to no avail

We are now thinking it’s the relay on the flip side of the fuse board- see pics

Anyone done this yet? I think it’s the tyco relay…

IMG_9761.pngIMG_9760.png

Stuart! Yes! Exactly my point, it is likely to be that one because its a git to change.
I'm just going to suggest putting the roof down.

bigwinn · Post by **bigwinn** » Tue Apr 30, 2024 7:37 pm

Come on! We can fix it!

bigwinn · Post by **bigwinn** » Tue Apr 30, 2024 7:53 pm

Steve has procured a new fuse board so we will swap it out to see what happens

enuff_zed · Post by **enuff_zed** » Tue Apr 30, 2024 8:00 pm

bigwinn wrote: ↑Tue Apr 30, 2024 7:53 pm Steve has procured a new fuse board so we will swap it out to see what happens

I have a complete fusebox here.
Was contemplating swapping the whole thing.

colb · Post by **colb** » Wed May 01, 2024 12:42 pm

Seen a couple of cars with duff defoggers but not explored the cause on either so watching the progress you make. If it is that relay on the board then trying a different fuse board probably worth a go. The two cars I have seen it may be a simple fix for them.

Rossi1001 · Post by **Rossi1001** » Fri May 03, 2024 7:42 pm

bigwinn wrote: ↑Tue Apr 30, 2024 7:53 pm Steve has procured a new fuse board so we will swap it out to see what happens

Some amazing knowledge on this thread! Thank you!

Stuart do let me know what happens with your car! Martin is helping out in June sometime, so there's a bit of time yet before we have a go at fixing this. I wish it was just a simple fuse change!

Z4-forum.com

Z4-forum.com