NEWB Here first question is on Vacuum sensor

[holanae]

Hello, traded my lightning even up for a 2004 F250 CC. I thought I would be sad to see my lightning go. I love this diesel. Anyways, I am reading as much info as I can about these trucks. The newb sticky was a informative read and I plan on doing most of the things listed before I even start to mod this truck in any way. The engine bay is pretty dirty, but I will have it cleaned up like my lightning's was. It has the oil look that I have read about that needs the seperator installed, just like the lightning needed.
Now to my question. There is a vacuum sensor on what looks to be one of the heater lines going to the heater core. It is missing the vacuum lines to it. It appears that there are possibly two going to this assembly. I think I found one but I don't know which side it goes on. I can't locate the other line. Can anybody help me. Pictures attached.

[Lilpooh]

It's the gray line that is in the pic, it's probably slipped over the nipple/stud on the HVAC box. On the inline vacuum valve, it goes on the front nipple, the nipple facing toward your grill.

[holanae]

So the grey line in the pic goes on the inlet side. What goes on the other end (the outlet side)?

[dazdillenger]

That is a valve-it closes off coolant flow to the heater core when the ac is on to keep it as cold as possible. The only line that goes to it is a grey plastic line. That line is usually put on a nipple on the heater box on trucks without the valve. There is no vacuum outlet, just one connection! They may have it disconnected because of a bad valve that leaks-if the ac blows on defrost only when it's hooked up, you'll know why!

[holanae]

Yes, I've noticed that the ac doesn't blow out of the dash vents at first. How do I fix that? Does that valve need to be replaced?

Would that be what was causing the AC system not to blow very cold all the time. The ac system pressure is good.

[dazdillenger]

The ac vents get switched by vacuum-when they are slow to switch, or blow out the defrost, you have a vacuum leak somewhere. That valve won't cause them to not switch, but if it is bad and leaking it could, but only on max ac. If the vents take a few seconds to change, look for a leaking line-usually to the front hubs on 4x4.

[Ryan Rønning]

Welcome to the ORG!

[holanae]

there is no vacuum coming from that disconnected line. It should pull a vacuum only during Max A/C correct? I will have to trace it back to find out where it is leaking from.
I also noticed that the air doesn't blow out harder when I go from regular a/c to max a/c. Any ideas on that one, or does it blow at the same rate when the a/c is on regular or max? I know in the my other lightning when you switched from regular to max, it blew harder.

[dazdillenger]

Yes, it should produce vacuum when you put max a/c on. Get a vacumn gauge/tester and test the system. Most leaks can be traced to the vacuum lines for the esof.

As for the a/c not blowing harder when it is set to MAX, it should as MAX allows outside air to be pulled in, allowing the blower motor to spin faster as it is working less. When you set it to a/c from max, it should switch to recirculate, and the blower has to work harder.

Basically it sounds as though you have a vacuum leak. Time to start searching! Is your vacuum pump running with the key on? Does it stay running, or does it shut off after a while? Once the vacuum resovoir is filled it should shut down. The resovoir is bolted to the inner fender on the passenger side. It is an oval box with 2 ports.

[holanae]

Found the leak, but won't know if everything is working until tomorrow. Appears to be though. Thank you dazzdillinger.