1. Iím not sure if I can help you much on this one, but sounds like some connection(s) are loose or has hairline cracks and changes with movement and/or temperature (metal expanding and contracting). I had this problem in my 190 when I was checking the values on all the 5 sensor that feeds info to the push button controls. I didnít have a tester like you but the ďintermittentĒ that you mentioned was exactly every 20 seconds in my case. This pointed me to the outside temperature sensor. Sure enough when I hook up the DMM to it the readings would fluctuate when I wiggle the cord around. I didnít see any cracked cord so I try resoldering the connections. Hook up the DMM again got study reading, I test for correct resistance at different temperature by first putting it in the freezer then heat it up with my wifeís hair dryer (not to long or to hot!). Hope this helps some.
2. Some people in this forum suggest the push button control unit itself. What you do here is open the unit up and resolder everything, from age the solder becomes loose and/or has hairline cracks from vibrations. This should be your last resort.
3. The other reason Iím here is to ask you if you ever got your Flashers fixed. I got the same problem in my 260E, the high-beam works but flashers donít. See and answer back at this post: Flashers
Thai GI sends...