I have the same problem as many with my AC/Heat deciding to blow from the defrost vents only. After reading through these forums I figured the fix is to install the check valve (pn 4677204), so I picked one up. Even with the service bulletin, I cannot figure out where to install the valve.

Can someone help me with a detailed description or pictures to show where it should be installed on a 1996 Grand Cherokee? Also, which direction does the valve go? I'm trying to save a few bucks... the part was cheap enough, but they wanted $80 to install it at the stealership.

Paul

Take a much harder look at your vaccuum hoses all over. I dealt with this during the heat this summer and found where a line going in through my firewall had been rubbing and finally developed a leak. The minute I had it patched the vents were working again. I patched it quick by using the crevice tool from WD/40 or PB Blaster inside to bridge the line but later a small piece of fuel line for a RC engine did a perfect patch over the break. Too dark now to get a pic maybe I can get one tomorrow.

And you're not gonna believe the check valve, I mean checking your oil is probably harder than putting in a new one.

http://www.twocanines.biz/images/vacuum_line_repair.jpg

http://www.twocanines.biz/images/check_valve.jpg
Tough to photograph, orient the valve so that vacuum is allowed into the engine block.