I've got an '85 Crew cab which was converted to a Cummins using a '92 W250 donor....I swapped over the a/c box, lines, EVERYTHING in the engine compartment. I had the A/C working for a while but now it will only blow out of the defroster vents. Looking on the hood I see two vacuum hoses (plastic) going into the firewall area on the passenger side. One is very short and actuates what appears to be a heater control valve. The other is longer and is just hanging loose! So I'm thinking that one came off of somewhere and that is why my air wont switch over to the dash vents.

Problem is, I have looked all over the engine compartment and do not see where it was plugged in??

Can someone pop their hood and take a look? I was thinking it might feed off the brake booster, but that has a rubber nipple on the very end that is just a block off, and that is the way it was on the W250 (I swapped the entire brake booster/master assembly without modifying anything).

thanks!

 

On my truck there are only 2 vac hoses coming out where you are referring to. One goes to the hot water control valve on the heater hose and the other (the long one) is the vac supply from the tee at the brake booster. That wouldn't make sense if your ac worked before, but thats where mine goes.

 

For some reason your post only showed partially the first time I read it. Yes the long hose goes to the nipple on the booster, Where were you getting the vac supply when the ac was working?

 

thats what I don't understand/remember....I just don't recall where that long vacuum hose was connected I did look at a friends '93 W250 and his is also connected to the nipple off of the brake booster like y'all mentioned. Looking at mine, it just has a blocked off rubber fitting where the nipple would go. And I can tell it has been there for a long time, you can even see how it is starting to dry rot some from age. My donor truck was an original TX truck with a/c, i can't imagine the previous owner having driven it without a/c? Plus it was a very low mileage/original truck.

Oh well, i will go and get one of those vacuum trees that I can put on the booster and see what happens.

 

The line supplies vacuum for the position motors and heater valve. the AC would work, but it would just blow where ever it was at. Hitting a big bump could have moved it. It may have been plugged because it was leaking vacuum under the dash.