Defrost Control Knob

[seawolf71]

Hi- on my 71 280 there is this round knob just to the right of the heater levers and above the clock that says defrost with a blue arrow that indicates an adjustment-what does this do and should anything be done to it while I have the dash apart? Thanks  Bill 71 280SL 

[Jonny B]

this is the fan control switch, and you should be able to hear the heater fan spooling up and down as you adjust. I have an early car, with the lighted switch and no marking, but the function is the same. I think you will hear a pretty sedate change of speed. As with cars today, the defrost setting should be the highest speed to push as much air as possible to the windshield.

[seawolf71]

Thanks Jonny B- looking at the switch closer,I think it is a rheostat type, but I'm not sure because I can't get that nut with the two slots to budge. Any ideas as to where I could get a wrench or other tool that would fit it?   Thanks again for your help. Bill 71 280SL

[Jonny B]

When I replaced my switch, I do not remember using any special tool. I was able to access the switch by taking the glove box out and getting it from behind. I am traveling and am not able to take a look at the set up. I am sure there are others that will respond with further recommendations.

[seawolf71]

Jonny- I was able to get the blower switch out by using a small screwdriver and hammer!!!!,and CAREFULLY tapping the slots on the nut holding the switch to the dash. there is a spring washer to hold the switch tight to keep it from turning I presume. I cleaned the rheostat in the blower switch with Tuner cleaner & lube and will try to test it to see if my blower works. Has anyone done this before? Any info would be great. Thanks again.  Bill 71 280SL