ACC fan revs up and down...
 

87 300D turbo.

The interior fan seems to go fast sometimes, slow others. I put it on max or auto and min on temp setting. AC seems to work fine. Put it on low speed and I get low speed fan. Anything else and it goes up and down on speed.

If I put it on the fast fan speed, shouldnt it go all out, regardless of what it thinks temp inside vs set is? I set temp wheel on min also.

I tried wacking the dash as few times, this didnt seem to help (although its a bomb shelter inside, according to 5th gear videos).