A/C question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**leddzepp** · 11-23-2008, 01:41 PM

My A/C works as far as holding a charge. I am wondering if my vacuum lines are routed properly. When the A/C is ON (all 3 levers pulled to the left) should the recirculating air door (by the kick panel) be open or closed? And should the outside air door (in the cowl area) be open or closed? I think the PO may have routed the lines incorrectly, or has the vacuum actuators reversed. When the A/C is ON, one should be open, and one should be closed, correct? Or should both be closed? Thanks for the help.

Andy4639 · 11-23-2008, 01:53 PM

This should help the diagram is in this post.

http://67-72chevytrucks.com/vboard/s...d.php?t=315714

**leddzepp** · 11-23-2008, 02:16 PM

Quote:

Originally Posted by Andy4639

This should help the diagram is in this post.

http://67-72chevytrucks.com/vboard/s...d.php?t=315714

I saw that earlier...A/C is a little different, thanks though.

**john** · 11-23-2008, 03:13 PM

That is the correct A/C diagram. Non A/C trucks do not have vacuum control.

**leddzepp** · 11-23-2008, 03:29 PM

The Diagram is somewhat helpful, thank you. I am trying to figure out if he has the lines reversed. Also, does the drivers side vent have any effect? I open and close it, and it seems to make no difference in my airflow either way. When all my levers are to the left, the kick panel vent on the pass side closes (shouldn't it open?)

Luis_gz06 · 11-23-2008, 04:41 PM

Quote:

Originally Posted by leddzepp

The Diagram is somewhat helpful, thank you. I am trying to figure out if he has the lines reversed. Also, does the drivers side vent have any effect? I open and close it, and it seems to make no difference in my airflow either way. When all my levers are to the left, the kick panel vent on the pass side closes (shouldn't it open?)

Hey Scott, I don't think the driver's side vent makes any difference at all. That's a manual vent that you open or close anytime for outside air with or without the a/c being on. Also when I turn the a/c on in my truck, the passenger side vents opens. Many people told that's the way it is.

Andy4639 · 11-23-2008, 04:53 PM

leddzepp,

Quote:

I saw that earlier...A/C is a little different, thanks though.

What is differant? The picture is for A/C on our trucks. This is a factory setup on all years as far as I know.

**leddzepp** · 11-23-2008, 05:03 PM

Andy- My bad, you are correct. The PO jacked up and bypassed and jury-rigged so many vacuum lines on my truck that it really got me confused. The least of which, I think he got the lines reversed on the back of my A/C controller. When I turn the A/C on, with all levers to the left, the kick panel door closes, and the cowl door opens. I think it should do just the opposite?? Thanks for your input Luis, this is what I thought and helps to confirm my suspicions.

How do I connect the lines to the vacuum reservoir? I do not think it is even being utilized, as there is only 1 line connected to it. Which is in and which is out? It looks like from the diagram that the source goes into the bottom, and the output line goes on the top. Thank again for all the input.

JimKshortstep4x4 · 11-23-2008, 07:30 PM

The vacuum supply fitting on the reservoir is larger than the fitting for the hose that goes to the vacuum switch.

Jim

**leddzepp** · 11-23-2008, 07:36 PM

Thanks Jim! All the info is helping, and starting to make sense of this mess. Thanks again for your pic in my other post about the return spring. I got the kick panel door to open and shut...just need to get it to do it at the right setting now! I think I am going to go to the parts store and get new vacuum line and connecting tees, and just start over, following the diagram. My A/C is super cold, but the volume of air being put out is super weak. It also looks like in the diagram that the vacuum supply line going into the dash A/C controller is on the right side port (looking down at it) This is where I think the lines have been reversed.

**leddzepp** · 11-23-2008, 10:21 PM

My A/C controller has 3 ports on it...not 2 as shown in the above diagram. Any reason for this?

**clay68c10** · 11-23-2008, 10:28 PM

With the levers all to the left, your kick panel vent should open and the cowl flap should close. That way the fan pulls recic air from inside the cab thru the kick panel vent.

**clay68c10** · 11-23-2008, 10:30 PM

Mine has 3 also, get a vacuum pump and see what is what. I don't remember which port is which but I think it was 1 vacuum source from the manifold/reservoir and 2 outputs.

**leddzepp** · 11-23-2008, 10:55 PM

Thanks for the info Clay. I will try to isolate them and see what is what. It makes sense to me about the ports being 1 in and 2 out. I am wondering if the second output would go to the water valve to better split up the vacuum between the 2 actuators and the water valve?

**clay68c10** · 11-23-2008, 11:03 PM

That's sort of how I did mine, I split it up in-cab/under-hood.

badpeanut · 11-24-2008, 01:05 AM

Quote:

Originally Posted by leddzepp

My A/C controller has 3 ports on it...not 2 as shown in the above diagram. Any reason for this?

My original had 2 ports, but my replacement has 3 ports so I plugged one.

**leddzepp** · 11-24-2008, 03:56 AM

Thanks badpeanut. I am off to the parts house to buy vacuum hose and connecting pieces. Going to follow the diagram and everyone's info. They are old (not cracked) and need replacing as it is.

JimKshortstep4x4 · 11-24-2008, 08:48 AM

leddzepp,

Check your water valve before you you redo all of the vacuum lines. Trucks originally with the 3 port controller applied vacuum to the water valve to open it. On the 2 port controller the vacuum was used to close the valve.

The two port system is more simple and if your valve closes with vacuum then my suggestion would be to do as Bad Peanut did.

Here is the vacuum diagram for the original 3 port controller.

Jim

**leddzepp** · 11-24-2008, 12:00 PM

Thanks for the diagram Jim, that is a tremendous help. My only question is, why would the valve be open on one system, and closed on another? Would that not make a difference in your A/C temperature if the valve is open and allows the core to heat up? It makes sense to me the valve should stay closed as in the 2 port diagram.

Andy4639 · 11-24-2008, 04:55 PM

leddzepp,
What he is saying is:

Trucks originally with the 3 port controller applied vacuum to the water valve to open it.

On the 2 port controller the vacuum was applied to close the valve.
The valve is shut on both systems just the vacuum use changes. Hope this helps.

**leddzepp** · 11-24-2008, 06:23 PM

Andy- So what you are saying is that the water valves are different? How can vacuum applied open the valve, but on another controller close it if the water valves are the same thing? I have looked at the water valves for sale, and they are all listed the same from 67-72. Sorry, I guess I am stupid but this does not make sense to me.

11-23-2008, 01:41 PM	#1
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	A/C question My A/C works as far as holding a charge. I am wondering if my vacuum lines are routed properly. When the A/C is ON (all 3 levers pulled to the left) should the recirculating air door (by the kick panel) be open or closed? And should the outside air door (in the cowl area) be open or closed? I think the PO may have routed the lines incorrectly, or has the vacuum actuators reversed. When the A/C is ON, one should be open, and one should be closed, correct? Or should both be closed? Thanks for the help.

11-23-2008, 01:53 PM	#2
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: A/C question This should help the diagram is in this post. http://67-72chevytrucks.com/vboard/s...d.php?t=315714 __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

11-23-2008, 03:13 PM	#4
john member #16 Join Date: Dec 1999 Location: Yuba City Ca. Posts: 3,618	Re: A/C question That is the correct A/C diagram. Non A/C trucks do not have vacuum control. __________________ john http://67-72chevytrucks.com/vboard/showgroups.php board vendors http://www.flickr.com/photos/1745471...7602865984234/

11-23-2008, 03:29 PM	#5
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: A/C question The Diagram is somewhat helpful, thank you. I am trying to figure out if he has the lines reversed. Also, does the drivers side vent have any effect? I open and close it, and it seems to make no difference in my airflow either way. When all my levers are to the left, the kick panel vent on the pass side closes (shouldn't it open?)

11-23-2008, 05:03 PM	#8
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: A/C question Andy- My bad, you are correct. The PO jacked up and bypassed and jury-rigged so many vacuum lines on my truck that it really got me confused. The least of which, I think he got the lines reversed on the back of my A/C controller. When I turn the A/C on, with all levers to the left, the kick panel door closes, and the cowl door opens. I think it should do just the opposite?? Thanks for your input Luis, this is what I thought and helps to confirm my suspicions. How do I connect the lines to the vacuum reservoir? I do not think it is even being utilized, as there is only 1 line connected to it. Which is in and which is out? It looks like from the diagram that the source goes into the bottom, and the output line goes on the top. Thank again for all the input. Last edited by leddzepp; 11-23-2008 at 05:30 PM.

11-23-2008, 07:30 PM	#9
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: A/C question The vacuum supply fitting on the reservoir is larger than the fitting for the hose that goes to the vacuum switch. Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

11-23-2008, 07:36 PM	#10
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: A/C question Thanks Jim! All the info is helping, and starting to make sense of this mess. Thanks again for your pic in my other post about the return spring. I got the kick panel door to open and shut...just need to get it to do it at the right setting now! I think I am going to go to the parts store and get new vacuum line and connecting tees, and just start over, following the diagram. My A/C is super cold, but the volume of air being put out is super weak. It also looks like in the diagram that the vacuum supply line going into the dash A/C controller is on the right side port (looking down at it) This is where I think the lines have been reversed. Last edited by leddzepp; 11-23-2008 at 07:41 PM.

11-23-2008, 10:21 PM	#11
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: A/C question My A/C controller has 3 ports on it...not 2 as shown in the above diagram. Any reason for this?

11-23-2008, 10:28 PM	#12
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,990	Re: A/C question With the levers all to the left, your kick panel vent should open and the cowl flap should close. That way the fan pulls recic air from inside the cab thru the kick panel vent. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

11-23-2008, 10:30 PM	#13
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,990	Re: A/C question Mine has 3 also, get a vacuum pump and see what is what. I don't remember which port is which but I think it was 1 vacuum source from the manifold/reservoir and 2 outputs. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

11-23-2008, 10:55 PM	#14
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: A/C question Thanks for the info Clay. I will try to isolate them and see what is what. It makes sense to me about the ports being 1 in and 2 out. I am wondering if the second output would go to the water valve to better split up the vacuum between the 2 actuators and the water valve?

11-23-2008, 11:03 PM	#15
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,990	Re: A/C question That's sort of how I did mine, I split it up in-cab/under-hood. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

11-24-2008, 03:56 AM	#17
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: A/C question Thanks badpeanut. I am off to the parts house to buy vacuum hose and connecting pieces. Going to follow the diagram and everyone's info. They are old (not cracked) and need replacing as it is.

11-24-2008, 08:48 AM	#18
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: A/C question leddzepp, Check your water valve before you you redo all of the vacuum lines. Trucks originally with the 3 port controller applied vacuum to the water valve to open it. On the 2 port controller the vacuum was used to close the valve. The two port system is more simple and if your valve closes with vacuum then my suggestion would be to do as Bad Peanut did. Here is the vacuum diagram for the original 3 port controller. Jim Attached Images __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

11-24-2008, 12:00 PM	#19
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: A/C question Thanks for the diagram Jim, that is a tremendous help. My only question is, why would the valve be open on one system, and closed on another? Would that not make a difference in your A/C temperature if the valve is open and allows the core to heat up? It makes sense to me the valve should stay closed as in the 2 port diagram.



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11-24-2008, 04:55 PM	#20
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: A/C question leddzepp, What he is saying is: Trucks originally with the 3 port controller applied vacuum to the water valve to open it. On the 2 port controller the vacuum was applied to close the valve. The valve is shut on both systems just the vacuum use changes. Hope this helps. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

11-24-2008, 06:23 PM	#21
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,031	Re: A/C question Andy- So what you are saying is that the water valves are different? How can vacuum applied open the valve, but on another controller close it if the water valves are the same thing? I have looked at the water valves for sale, and they are all listed the same from 67-72. Sorry, I guess I am stupid but this does not make sense to me.

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