For the 87, the only time you have a light is WHEN the fault is occuring...
As for the other car, I think that Steve's solution is the only one. I think you are having someone other than a Mercedes Tech do the work, aren't you? Any Mercedes Independent should be able to clear and check for codes in these and other systems.
[This message has been edited by Benzmac (edited 07-09-2000).]