There were a number of changes in control unit numbers. The system was basically the same in 88 and 89 so I would guess the other unit would work just fine. I have a number of units that we use interchangably as test tools.

Since the control unit is almost never the problem, one will never know if the reason it doesn't work (after replacement) is the wrong part though, unless one gets the exact right part.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician