HVAC Vacuum : Thanks

[wthif]

Just a couple of question about vacuum and HVAC controls.

Where does the vacuum line come through the fire-wall for the HVAC controls? What kind of route does it take once in the cab? Does the HVAC controls need vacuum in order for the AC to cycle?

I've been lazy, I know I can answer some of these questions on my own but... :rolleyes: Thanks for any help.

Oh one last question does the AC cycle with the defrost on?

[ 10-19-2005, 07:50 PM: Message edited by: wthif ]

[FredM]

the vaccum line is small plastic tube it tee's off at around the rear of the passenger side valve cover between it and the firewall. check if you have vaccum at the pump first the HVAC control comes out as a unit you'll see the line when you pull it out.

[wthif]

I guess I should of mentioned how lazy I really am. I know where the vacuum lines are, but don't know the route they take once they enter the cab through the firewall. Also all my lines were disconnected when I swapped my engine out for Britannic's. I have two vacuum pumps so not worried about finding if they work just want to know where the lines run. Trouble shooting isn't my problem finding the lines in the cab is the problem.

I will connect the vacuum up to the line entering the cab and try that.

Still wondering if the ac cycles when HVAC controls are set to defrost? Also I guess it is important to say that the AC has never worked in my truck since I bought it. I will be fixing/converting the AC system with a York compressor for next summer.

[BobND]

Yes, the AC compressor cycles to dehumidify the air when the controls are set in the "defrost" postion.

[wthif]

Where does the vacuum feed line for the HVAC controls connect to the HVAC controls? Have dash apart not quite sure where it connects. I do see all the small lines coming off the HVAC controls but don't see where a vacuum feed line would connect. The HVAC controls are the only thing on my truck that I want vacuum connected to. Nothing else that originally needed vacuum is there any more. Also the pervious owner didn't know a thing about electrical or vacuum and all lines behind the dash are butchered up.

[HammerWerf]

wthif,

I looked at my 83 and 84.

The vacumm line enters the cab through a penetration on the passenger side of the cab. It is located behind the fuel filter, probably under the heavy shield that covers the HVAC system in the engine bay. Once inside, it travels along the firewall to the HVAC controls, passing behind the duct work. From my looking at the controls in my truck, I think this line connects to the controls in the center, pointing toward the steering wheel. It looked like it is attached to a different portion of the controls. The lines that do the actual controlling are attached to the round selector on the right. The inside the cab directions are you sitting in front of the controls.

I have a couple of pictures I took to show what to look for. I can email them to you if you like. Send me an email at :

hammerwerfer1976@yahoo.com

My dash cover is currently off, so it's easy to get the pictures you might need.

Are you trying to figure out where each vac line starts and terminates?

The vac system only controls the HVAC system.

HammerWerf

[wthif]

Originally posted by HammerWerf:
The vacumm line enters the cab through a penetration on the passenger side of the cab. It is located behind the fuel filter, probably under the heavy shield that covers the HVAC system in the engine bay. Once inside, it travels along the firewall to the HVAC controls, passing behind the duct work. Thanks for the info I found where the vacuum line once entered the cab on the drivers side because of other vacuum related controls. Now I'll look for the vacuum line on the other side.


Are you trying to figure out where each vac line starts and terminates?I'm currently not try to figure out where each vacuum line terminates but if they don't work once they get vacuum I might be.


The vac system only controls the HVAC system. I know that the vacuum mainly controls the HVAC but on mine it once controlled the Cruise Control and the TH400 neither or which are around anymore.

Thanks for all the help. I'll be checking it out this weekend and post with any success.

ON EDIT:
HammerWerf are you a werfer (hammer thrower)? I'm friends with someone who did the Hammer throw in the Olympics.

[HammerWerf]

wthif,

Yep, I threw hammer for the Florida Track Club in the mid to late 70's. Had lots of fun.

How is the investagation going?

HammerWerf

[wthif]

The investigation isn't going that well. Could anyone with a 82 pickup (81 also might be the same) confirm where the vacuum line for the ac controls enters the cab through the firewall. I have a line about 1/8" in diameter coming out of the firewall on the passenger side of the ac box. Is this the line I need to connect? I'm going to try it but doesn't seem like a main vacuum line; looks more like one that left the HVAC controls. HammerWerf was kind enough to send me a picture of his firewall where the ac vacuum line entered for his truck, but his firewall appears different than mine. I'll try to post a picture of the vacuum line in question this weekend.

ON EDIT:
Posted is HammerWerf's picture of where his vacuum line enters.
http://home.earthlink.net/~mtnmike/sitebuildercontent/sitebuilderpictures/hwfirewall.jpg

[ 10-14-2005, 11:11 AM: Message edited by: wthif ]

[arveetek]

Yep, my '81 has a very small vacuum line coming out of the firewall next to the a/c evaporator housing, between the housing and the tranny hump, about halfway down the firewall. This small line goes over the top of the a/c evaporator and then plugs into a small vacuum reservoir, about the size of a softball, which is bolted to the firweall, between the fender and evaporator housing, above the blower motor. From that point a much larger line leaves the reservoir and goes to my vacuum pump.

Of course my '81 was originally equipped with a gasser, but it should be similar.

Casey

[wthif]

Originally posted by arveetek:
This small line goes over the top of the a/c evaporator and then plugs into a small vacuum reservoir, about the size of a softball, which is bolted to the firweall, between the fender and evaporator housing, above the blower motor. From that point a much larger line leaves the reservoir and goes to my vacuum pump. I have no reservoir. Is this a diesel thing or is the reservoir MIA on my truck?

[arveetek]

Like I said, mine was originally a gasser, so I don't know if the diesel-equipped trucks have the reservoirs or not.

It looks like my small vacuum line comes out in the same place as in the picture you posted. That's the main line for the HVAC controls.

Casey

[wthif]

Well after posting that last post something clicked in my mind and I realized that there was a reservoir it just isn't on my truck anymore. I couldn't remember where it went, then it hit me I took it off when I did the engine swap at Brittanic's place. We did the engine swap during the winter so working in freezing temperatures was common and I blocked a lot of the swap form my memory out. tongue.gif

Does anyone know if I can just hook a vacuum supply up to the reservoir and the small vac line coming from the firewall to the reservoir, to make the HVAC controls work?

Thanks everyone for the help so far. smile.gif

[BobND]

Yes, that is how you would hook it up,

[wthif]

I would like to say thanks to all that helped me figure out my vacuum problems. My HVAC controls actually control the vent baffles and I now can get air blown in my face or on the windshield, and of corse the floor. I am now ready to tackle my next project of retro fitting two York compressors to my engine. One for AC and one for OBA.