Default no vacuum present at the Distribution system in the dash the heat will only come from the Defrost Vents and side vents and will be full heat. Not sure where your distribution electronic vacuum thing is in the 300, but in the 190E it is under the passenger side vent in the dash and most lines and connections can be checked by removing the lower passenger side dash panel and the glove box, along with taking out the radio and lower panel under it.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....