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In my post "HVAC '84 733i Is this particular problem"...
I described the deterioration of the fan thumbwheel's ability to activate the fan and any control other than the DEFROST setting. All the usual stuff worked, had vacuum etc...Randy suggested cleaning the microswitch contacts on the thumbwheel board and it worked!!! Thanks Randy!!! This was my first time in there so I will summarize the steps for other novices.
Hope I did not miss any important steps. First time in is always exciting...
--Don'ts:
Do not have to remove any console parts.
The microswitch is the black thing on the board; at first I misinterpreted Randy to mean clean the thumbwheel contacts; that did not solve it.
--Do's:
Disconnect negative battery cable
Remove ashtray and 4 screws
Remove 2 screws behind the ash tray cover at top that hold the heater/radio panel
Remove the radio(depending on your installation)
Remove 4 screws along top of heater/radio panel.
Dont think you have to remove the 2 bolts under the radio; I think they are for console.
slide panel out; a rubber hose connecting the temperature sensor to the panel/grill pops off. (never got that back on yet)
remove top thumbwheel connector, ligth bulbs etc.
remove 1 screw from each side of the thumbwheel board cover.
remove 3 screws holding thumbwheel board in place
remove assembly;
remove cover
WATCH for small spring and ball bearing(temp. thumbwheel) as you remove the 3 cover screws and unsnap cover from board
drill out 2 large rivets holding the microswitch to the board with approx. 2.0 mm drill. Be sure to hold the switch securely or else you will break the switches solder lugs( I did)
The third smaller rivet holds the case together. drilling from the top (about a 1.0 mm drill) resulted in the rivet just spinning. So I proceded to break off the solder lugs(hopeful I could re-solder them) and dissassemble the switch cover while off the board. You could probably desolder the switch and remove it intact then resolder.
the cover comes off(now that 3 rivets are gone) and you can get 400 grit sand paper in there.
2 small (approx 2.0mm by 10mm long) screw/bolt/nuts hold the switch back on and the case together. I added some glue as "loctite" to prevent falling apart cause my screws were not long enough for lock washers.
Reverse procedure and SUCCEED!!!
I cleaned the thumbwheel contacts with 400 grit too; do not know if this was good or bad....
NOTE: Car is '84. thumbwheel board date was '92 92-84 = 8 years first time???? 2001 - 1992 = 8-9 years second time???....so maybe every 8 years????
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