The main problem with these displays is that when exposed to too much hot sun, the LCD panel ‘bleeds’.   Over time, this makes it increasingly illegible, not to be mention ugly.    I previously fixed the displays in both my old 300SE and the 560SEC.    The W124 outside temperature display is basically the same as the unit found in the W126 and W124.  They are just in different housings.

The good news is that replacement LCD panels are available.    The LCDs used changed in about 1988, so for the 300TE I needed to use the newer version of the LCD panel.    I also bought another earlier one to fix a spare W126 unit I have on hand.

The W124 outside temperature display unit just screws into the back of the instrument cluster.   Its the first thing you have to remove to get the gauges out, so now was a good time to repair it.

To repair the W124 unit, there are four small screws that must be removed.   On this model, the upper and lower parts of the housing must come apart to get to the front part where the LCD panel is.

The later unit as on my 300TE has a more sophisticated baffle for the bulb that illuminates the display.   Otherwise there are basically the same, with the two black ‘blocks’ that transmit the signal from the PCB to the LCD panel.     The dot at the top of the LCD panel faces upwards.

As I purchased two LCD panels, a new one and an old one, I had the issue of not being able to work out which was which.   Probably it would be evident with a strong magnifying glass, but I couldn’t tell.   I tried one, and as it turned out, it was the wrong one.    The W124 outside temperature display is a separate unit to the instrument cluster, so its possible to test it without installing the entire instrument cluster.

It also looks like the blub in my unit has blown.  It would be easy to change if you are good at soldering.   This is soldered onto the PCB, and I’m terrible at soldering.   For now, I’m going to leave it as is.    I’m still pretty happy with this repair.

The post Refurbishing a W124 instrument cluster – Part 2: W124 outside temperature display appeared first on Classic Jalopy.

Buying a used one is not really a good option.   They are not particularly cheap, and even if a cheaper one from the USA can be sourced, it would be in Fahrenheit.   There is somebody in Europe who is selling replacement LCD panels so I thought I would give it a go.

Obviously to get to the LCD, the instrument cluster has to come out.   I find the easiest way is to remove the drivers side speaker and push it out from the back.   The W126 outside temperature display is screwed into the bottom of the cluster and can be removed without any other disassembly.

Replacing the LCD is as simple as taking the front off and then swapping the panels over.

The little contacts on each side of the panel also need to come too.   When doing it, I couldn’t work out which side was the top.  I ended up guessing and I was wrong.   I guess I had 50/50 chance.

The backlight is also broken on my 300SE, so I dismantled the W126 outside temperature display to see if I could change it.   At first glance it looks like the little bulbs used in the dashboard.   However, its actually soldered to the circuit board.   My soldering skills are not up to this task so I don’t think I will replace it.

I got it back into the car and found two problems.   The first one is simple, I had the LCD upside down.   The second is more serious.   I didn’t read the description properly of the LCD, so didn’t specify I wanted Celsius.   The panel I have is for Fahrenheit which is useless to me.    So I guess that is about $65 down the drain, although I might be able to sell the panel.

I’ve now ordered two new panels to do the job properly and learn from my mistakes this time.

Despite my careless buying I feel good about this improvement.  The repair can be done without soldering, and seems to work quite well.   I should now have working temperature displays in these cars once the new LCD panels come in.

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