Intermittent Gauge Operation
 

Since I bought my used 1994 C-280 W220 with 70K the gas gauge would typically fail to wake up right away, especially when cold and sometimes when wet. Eventually and not predictably the gauge would return to the proper level. This could happen in 2 or 32 minutes - there's no telling. Even after working properly, shut down and re-start might result in the same temporarily dead condition. When it's dead, the low level light still functions. Now recently my coolant temp gauge is doing the same thing, waking up eventually.

I've seen a lot of comments via the search function about the wiring harness on these cars - but nothing like I have been experiencing.

Does anyone have a clue as to what is happening and where to look for a possible ground fault or loose connection? All other gauges work properly / no fuse has blown. With 106K on it the problem seems to be worse, but it hardly ever happens in the warmer months.

Most common problem on the W202 for the fuel gauge is the fuel gauge sender in the tank needing a replacement.

My gas gauge used to act jumpy, particularly around the 1/4-1/2 tank marks. It would read a higher 1/2 tank left and then suddenly drop to the correct 1/4 tank full. My habit at that time was to keep a relatively low tank level, i.e. fill up $20 dollars worth when empty. Searching the boards indicated the sender unit might be faulty. Some people replaced the unit only to have the condition continue. I have since kept the tank between 1/4 to full and the problem has gone away. But since your coolant gauge also acts up, it sounds like something electrical.

glenmore
1991 300CE
1990 LS400