S204 - Blank screen after stock head unit plugged back in

[Wuffles]

Hello, you might remember me from my previous thread about changing head units and the start/stop buffonery of the installer I chose to use. Posting this in a new thread as my last 45 message thread is a bit of a pain to go through, and is now mostly irrelevant.

Anyway, I'm back to stock head unit, couldn't be bothered with the hassle any more.

However, the Mercedes screen at the top of the dash no longer displays anything, rendering even the stock unit more or less useless unless all you want is the radio station that's already preset. Bluetooth, clock set and anything useful relies on the information on the screen.

Rear of screen is connected, I've checked that. I've tried pulling fuse 26, which some youtube video suggested fixes this kind of thing. I'm assuming because the battery was changed whilst the head unit was removed, the car has forgotten about the screen element? Dunno, clutching at straws.

Any suggestions?

 

[markjay]

Hello, you might remember me from my previous thread about changing head units and the start/stop buffonery of the installer I chose to use. Posting this in a new thread as my last 45 message thread is a bit of a pain to go through, and is now mostly irrelevant.

Anyway, I'm back to stock head unit, couldn't be bothered with the hassle any more.

However, the Mercedes screen at the top of the dash no longer displays anything, rendering even the stock unit more or less useless unless all you want is the radio station that's already preset. Bluetooth, clock set and anything useful relies on the information on the screen.

Rear of screen is connected, I've checked that. I've tried pulling fuse 26, which some youtube video suggested fixes this kind of thing. I'm assuming because the battery was changed whilst the head unit was removed, the car has forgotten about the screen element? Dunno, clutching at straws.

Any suggestions?

As far as I know, it's not the 'car' that is programmed to the screen, but the head unit. But it shouldn't really 'forget' the screen just because it was powered-off.

I am aware that it may be difficult to do, but ideally you'd want to be able to test the screen (and wire connecting to to the head unit) to know it is actually in working order.

The screen may have been damaged during the work by an unintentional short-circuit? Or the wire from the head unit to the screen may have been damaged? Or there may be physical damage to the connector on the screen or on the head unit (bent pins etc)?

 

[Wuffles]

Good knowledge there.

I'm reasonably happy there's no bent pins, certainly at the difficult to get at bit (screen end). When I initially fired up the stock head unit and the screen was blank, I assumed the fitters who attempted the 3rd party install had just disconnected it at the screen end, I don't know why, but when I took the dash apart to check it I realised it hadn't been disconnected at all. Which was a shame as that would have been an easy fix.

The head unit end looks all in tact to me, and would only have been disconnected and reconnected again perhaps a couple of times. Couldn't see any bent pins or damage. I could investigate further, I was really just hoping someone would say, oh that's common, press this and it'll all work again

 

[markjay]

Given that you can't really test it properly, I would look at buying a cheap second-hand screen and wire off eBay (make sure the MB part number matches), this will help with the process of elimination (and will be cheaper than buying a second-hand head unit). If the screen isn't the problem, you can always flog it back on eBay, you might make a small loss in the process but that;s the price of diagnosis. That, or wait for the garages to open and take the car to someone who know what they are doing (e.g. www.comandonline.co.uk) even it it involves a bit of journey.

 

[Wuffles]

Given that you can't really test it properly, I would look at buying a cheap second-hand screen and wire off eBay (make sure the MB part number matches), this will help with the process of elimination (and will be cheaper than buying a second-hand head unit). If the screen isn't the problem, you can always flog it back on eBay, you might make a small loss in the process but that;s the price of diagnosis. That, or wait for the garages to open and take the car to someone who know what they are doing (e.g. www.comandonline.co.uk) even it it involves a bit of journey.

Yes, pre-lockdown the agreed solution in the other thread about the Sony head unit was to drive up to Comand for them to get the 3rd party screen working, so if I did drive there for anything, I'd probably do that instead.