Engine/Transmission (1994 - 1998) AC Problem -- Finally found it!!!!

[Joe G.]

On our last trip to Oregon the AC controls quit so that the only place air came out of the system was the defroster vents. That problem is normally low vacuum. I tried to convince my wife that cold air out of the defrost vent was ok. She didn't buy that. I checked the vacuum at several places. It was fine. It was even ok where the vacuum line goes thru the firewall. I checked that as well as I could. With the radio out I could see the defroster door. It was not working. I finally gave up and took the dashboard out. That took about a day and a half. Now my garage looks like a truck blew up in it. Parts all over the place. I took the vacuum motor off the defrost door and checked it. (Oh yeah, my test pump makes about 300 HP. I was running it with the solenoid pulled up. ) The vacuum motor worked just fine. I took the message center panel over to my work bench. I ran a vacuum hose to the black connector and tested all the positions. Everything checked out. I put it back in the truck. Nothing. So I start to wonder if the black vacuum supply hose was plugged up. I tried to put some air to it and blew the line connector off. The picture below is what the first inch of the line looked like. It's kind of blurry because my camera can't get close enough, but you can see the collapsed place. I cut that piece off an put the connector back on the line. The vacuum controlled doors all work right now. I thought you would like to see this one. Might same someone from taking their truck apart. I hope I don't have to post a 911 before I get the truck all back together.



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[Joe G.]

Oops. Should have posted in the non-engine forum.

 

[velsberry]

I had the same loss of air through the main AC vents when my vacuum line under the battery developed a leak due to battery acid eating though it!

 

[willyslover]

Joe where was this piece of hose located ?? under dash ??

 

[Joe G.]

Gary,



It was just behind the rubber connector under the cowling just before the line goes thru the firewall. It was on the line to the firewall, not the line from the vacuum system. It's on the engine side of the firewall. It was impossible to see because the connector was in the way. Everything is black so that didn't help things. I found it by feel after I blew the connector off with air and I was putting the connector back on the line. If I had managed to find it sooner I would not have had to take the inside of the truck apart.

 

[Bob4x4]

That melted line is not rare,it runs close enough to the turbo (on a tow rig)to colapse and become a restriction and eventualy a total blockage.



Bob

 

[JKouzez]

i am having a believe a similar problem with my AC just outta the blue yesterday i noticed the AC would not turn on i messed with switch a little and found that if i put the selector in a sweet spot between recurculate and the top vents it would work. seems like a switch going bad to me any other ideas.