Originally Posted by kburks1230
The defrost vents in my 85 380sl never close. I always have air coming out and the cold a/c fogs my windshield which is kind of annoying.
You've got a bad vacuum pod. Unless they did a radical redesign, though, this is one of the easier vacuum pods to replace.
Take out your instrument cluster - to do this you'll need to remove your steering wheel and pull - literally - the cluster straight out. There's nothing holding the cluster in but friction. There are a lot of wires and connections going to the back, but most of them are very easy to take off and put back on. The only one that ever confuses me is the lights for the brakes and seat belt, and sometimes I get the two reversed.
Once you've got the cluster out, look inside the hole where it goes, down and immediately to the right. There should be a vacuum pod sitting there with a metal lever going up into the vent system. That's the pod that controls your defrost vents. I got a new pod for it from the local MB dealer, but there are other places to get them. I went to the dealer because I needed three of them, and I wasn't sure which was which from looking at web pages. I figured the dealer would know, and they did.
The only tricky part about it is getting the rivet out of the pod and metal lever without also pulling the lever off the flaps up inside, where it's difficult to fix. I didn't make it and that lead to another three or four weeks before I figured out a way to get it hooked back up without dismantling the dash of the car. If I had it to do over again, I'd have used a drill bit in my Dremel, so I could get a straight run at it. Trying to squeeze my cordless drill into the opening and getting the alignment right didn't work so well.
If you've got a Dremel and some patience, this is a 30 minute fix. If you've got a Dremel and no patience, it could be anywhere from a 30 minute to a 4 hour fix, depending on how badly your impatience screws things up. If you don't have a Dremel, I'd suggest getting one before attempting this.
You'll also need a replacement for that rivet you took out, to hook the lever up to the new pod. Unfortunately there's no way to know the size and length until you've got the new pod. Get a flat-head screw that will sit almost flush inside the opening in the pod and get the thinnest nut for it you can find. There's no extra room and if the screw head sits out too far, or if the nut it too thick, it'll bind up the actuator and you'll still have stuck open vents, just for a different reason. I got a screw that was too long, but I cut it off with the diamond cutter bit on my Dremel. Use thread lock to keep the things together after they're in.
This sounds more complicated than it is. Before you throw your hands up in despair take a quick look at it. Once you know where it is and what it looks like, the fix is obvious.