No heater/defrost controls ect...

[4benzes]

Fellas:
I am able to get ambient heat coming from the blower motor on the 86 735i, but when I depress each individual switch---nothing.
They will not stay depressed.
Also when I start the 735i, it idles at 2k for a while, whitout coming back down???


Thanks in advance,

[KC Ron Carter]

Described is 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... ,cleaning the microswitch contacts on the thumbwheel board and it worked!!!



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--Don'ts:

Do not have to remove any console parts.



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--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.

Don't think you have to remove the 2 bolts under the radio; they are for the center console,

slide panel out; a rubber hose connecting the temperature sensor to the panel/grill pops off,

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 DONE!!!

Cleaned the thumbwheel contacts with 400 grit too...





Now on the Idle, it is most likely an issue with the Idle Control Valve. Here is a procedure to clean and if that fails the kids at Pelican have new ones.


Idle Control Valve Cleaning - Rick Sparks


Have had a couple of requests to add this procedure to the FAQ, so herewith is what I did to clean the idle control valve on my '86 to solve idle surging from normal to 1500rpm on warm-engine startup.

The valve on my '86 is a round metallic cylinder about 1" long toward the back center of the top of the engine. The valve plugs into about the center of the black fuel injection boot, firewall side, and in turn has a black Bosch electronic unit plugged into it. Touch the valve when the ignition is on without starting the engine, and you should feel it humming.

1. To remove the valve, loosen the hose clamp under the valve that attaches it to a small rubber hose.
2. Remove the little nut that attaches the valve's metal support to the engine valve cover.
3. Unplug the black Bosch unit from the rear of the valve by squeezing the Bosch unit's wire lock together with your thumb & forefinger.
4. Remove the valve with the support attached, and then remove the support by squeezing in on one of the two little rubber plugs attaching the valve to the support.
5. Spray carb cleaner or penetrant liberally into one of the valve's two inlets, and it will run out the other. Spray into both inlets, and then let the spray all run out before reinstalling the valve. It may take a few minutes running the engine for the valve to fully loosen so it won't surge, but either carb cleaner or a good penitrant (not WD40 - one I like is Popular Mechanics "All Purpose Lubricant" available at Walmart) should do the job.
6. Reattach valve.

This procedure might prevent or postpone having to buy a new valve. It worked for me. Good luck.

[4benzes]

KC Ron:
Many thanks to you Bud!!!! I appreciate your time and help with this matter.