Good info ! Thanks.
My front vents operate well. All the vents and pods seem to operate.
My problem is with a high pitched sound coming from passenger side.
I was told the vac element can have a pin hole in it.


If I leave the air system ON all the time or on Economy, the noise is eliminated...

can vac test be done using the vac line 'junction' box in the engine compartment by the passenger side firewall or only from the 'junction' box inside the glove compartment rear???

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD