Hello,
I have an '87 740 wagon. I'm having problems with the vents that regulate airflow. My ac system works. At first airflow would redirect from front vent to defrost upon acceleration. Now there is barely any airflow at all. As if the vent doors are stuck in one position. I understand there are a number of hoses that regulate flow. My problem is, which one? I pulled my dash apart and the "box" is self contained and I see no real way to get into it. Is there a vacuum hose that comes from the engine? If so, where is it. You see where I'm going with this.............
Thanks in advance
Sean O

 

Hi Sean, your last sentence hits the nail on the head. The vacuum has to come from somewhere to work the vents. Since rubber has a nasty habit of deteriating with heat under the hood is the first and most likely place to look. What you want to look for is a vacuum hose that goes through the firewall. It most likely will have a two tone check valve on it. It will be small. Examine the ends of the hose for rot. Since I don't see you mentioning it being a turbo I'll assume it isn't. You can take a razor knife and cut a little of the ends of the hose to get a fresh portion that will seal on the nipples better. While you're at it, doublecheck all the vac hoses; they are often overlooked and when all of them leak a tiny bit each, it's like one big leak and affects performance.

 

Yessir. I'll be vacuum line fishing. I'll let you know what shakes out.
Thanks for the reply.
Sean O