i have an 89 300ce,when i push the button with both arrows up/dwn at times it blows strong air from the 2 center vents and floor,other times if i change it,or put it back,it can take about 3 mins for the center vents to blow air again,and sometimes other setting are delayed,is this a vacum issue,or do i need a new control unit?,i notice when on auto,the fan blows really low then goes up higher,it appears to work fine.some times center vent wont even blow air.

The center vents will usually only blow cooled air. Where do you have the temperature wheel set to? In auto mode the blower speed will increase if the temperature inside the car changes or is already considerably higher or lower than what you have it set for. This is to get the cabin to the optimum temperature as quickly as possible and to maintain the optimum temperature. Also if I'm not mistaken when in auto mode the car may not start blowing heated air until the coolant has warmed up sufficiently or engage the compressor until the oil pressure has built up.

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1989 300CE

Possible vacuum leak.

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Gone to the dark side

- Jeff

the center vents blow,intermitantly,but i have the cold setting all the way down to 65,but the a.c needs a charge,the compressor does not engage,its all origninal r12,it has low gas pressure,if i push in the high pressure port pin.i need to have it leak tested than recharged with the r12,i want to keep it all original.