I have been on the hunt for a cruise control system to retrofit to my car for some time now. Unfortunately they are very rare in the UK, and thus are expensive.
I have also been considering swapping my steering wheel for a later M-style one. This led me into looking at the earlier (pre 03/1999) e39 wheels, as they can be retrofitted into an e36 with minimal work. The advantage is that they are much more common, and I could get a multi-function wheel to use with my stereo (bonus)
This led to me thinking. Is it possible to use the cruise control system from that same e39 as well? The MF steering wheel would also include the cruise control buttons, and providing I got the wheel from a 6-cylinder 5 series (which has the m52 engine, same as later e36s) the actuator mechanism and brain should be the same (or very similar).
From looking on RealOEM, the part numbers and dates are different between the m52 e36 cruise systems and the m52 e39 systems, but the mechanisms look the same, and some parts are shared.
Crucially, the e39 system still uses a completely separate control unit ('brain'). It seems strange that BMW would produce two completely different systems to do the same job on the same engine when the two cars were being built concurrently. I figure the differences in parts were likely down to the different switching mechanisms (e39 had the switches built into the MFS, e36 was another, separate stalk).
If I pull the entire cruise system from an e39, including the MFS with the cruise buttons, the only 'connections' to my car would be at the throttle and the switches for brake and clutch. I feel that I can probably manufacture or adapt the system to connect to my car at these points.
There are two points I am still concerned about though. The first is that my car was built 2 months before a switch-over occurred for the cruise systems in the e36. The change was permanent for the rest of the e36 production run, and the cruise system remained the same for all m52s in the e36. Would my car be able to use the cruise system from a later m52 e36 without much trouble? Has anyone retrofitted cruise to a pre 09/1994 m50 engine using a cruise system from a later e36? If so were there any issues? Is the m52 throttle body a completely different design to the m50 throttle body, namely the connections for the accelerator cable and cruise control cable?
My second question is basically what people think of my idea and any possible problems?