DUTCH is correct - these gauges cannot be recalibrated, if your truck is a 1996 model with the M104. These systems work by converting the electrical signal received from the probe into a temperature display on the dashboard using a pre-programmed table in the display's logic circuit board.

If your truck has the small LCD readout at the center of the bottom of the instrument cluster, then the external temp system in the 1993-1996 models was shared with the E-class sedans from that era. 90 percent of the time, the issue is this digital temp readout that is embedded in the bottom part of the instrument cluster. What happens, is that one of the capacitors on the small circuit board goes bad, and the temp reads "off" by a set amount of degrees. Other symptoms of a bad display include black spillage of the LCD, or partial display of lines/numbers, or no display whatsoever.

I recently had this happen on my 1994 E500, where the temp readout was off by a constant 20F from the actual exterior temperature. You will need to remove the instrument cluster to replace this temp readout. It is held to the instrument cluster by two small Philips head screws, and the electrical connector of course.

The wiring is the wiring. It is relatively fixed in position and there is not much to fail. The probe at the end, of course, needs to be placed in the proper position at the front of the truck where it is least affected by engine heat, but if you never disturbed the position of the probe then you should be fine. Wiring usually doesn't fail unless it's been disturbed for some reason (example - the upper and lower engine harnesses on the 1993-1996 G-wagens, as well as the wiring inside the electronic throttle actuators on the G320 models).

A few bits of discussion on this at my site:

http://www.500eboard.com/forums/showthread.php?t=841

http://www.500eboard.com/forums/showthread.php?t=5547

And a youtube video on repair. It's dicey to repair these displays, yourself, but it can be done. https://www.youtube.com/watch?v=CHpzMeb1L0c

I pick up these displays all the time from wrecking yards - I have at least 10 of them. They are typically free or perhaps $5.00 to get from the yards. Cost from MB is over $600 last time I checked the price, so it's worth having a few spares. MB does sell them in both Fahrenheit and Celsius models, but of course for cars sold in the US it would only be the Fahrenheit version.

I am happy to send you one or two of my spares, if you would just PM me your address. Sometimes they work, other times not, so that is why I keep extras on hand. These are the same units also used on the Generation 2 W126 models produced from model years 1986-1991, so they are plentiful.

I also have a spare probe cable in my parts stock, for my E-class, in case I ever need it. These are also not cheap - for the W124 I think the spare probe cable was around USD $100.

I hope this helps.

Cheers, Gerry ] ] ]

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