73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: Smitty31 on February 19, 2018, 08:56:46 am
-
Does anyone have diagram for the a/c system for a 1986 c 10 4.3 automatic 2wd. Also do you have to hook up the fresh air. I like my air to recirculate in the cab. And that would be less vacuum lines to fool with. I can always open the vent doors manually.Your thoughts anyone.
-
Does anyone have diagram for the a/c system for a 1986 c 10 4.3 automatic 2wd
GM manuals by year model:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=30115.0 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=30115.0)
Also do you have to hook up the fresh air. And that would be less vacuum lines to fool with. I can always open the vent doors manually.Your thoughts anyone.
If installing a factory A/C system, probably better to keep the original setup that pulls fresh air from the cowl whenever 'Norm' is selected on HVAC control. If you desire recirculate, then 'Max' position will take care of that. You'll never notice the passenger vent is gone.
It helps if you have time to carefully remove the wiring and HVAC vacuum harness, without cutting anything, from the donor vehicle.
-
I pushed on time. The fresh air vent in the kick panel had a vacuum pull off in it. I was assuming that was for fresh air I look for a pic.
-
This is the pic
-
This is what I was wondering if I needed to hook it up or if I could leave it off
-
I downloaded the manual. I couldn't find anything on the vacuum lines diagram for the a/c system
-
I downloaded the manual. I couldn't find anything on the vacuum lines diagram for the a/c system
1986 Service Manual - Page 83 of 1584. Actual page in manual: 1B-20; Figure 20 - C/K A/C Vacuum Schematic
-
That is Greek to me but thanks for your time and effort. Does anyone know of a simpler easier to read diagram
-
That vacuum diagram and table is even more confusing than the one for my '75.
I believe this is what it it trying to tell you:
- There are nine ports on the back of the controls, but only five are connected. The others are plugged.
- There are five vacuum lines coming out of the back of the controls (lower right shows all the colors). These are the same lines/ports that are listed down the left hand side of the table.
- If you look at one of the control positions listed across the top, for example "Defrost". Then follow straight down and you will see the word "vacuum" on two lines.
- If you follow those lines with the word "vacuum" back to the left you will find that they line up with "Heater Mode"(port 3) and "OSA/REC"(Port 4).
- This means that if you put the controls in the Defrost mode, you should measure vacuum on Port 3 and Port 4.
- I can't quite figure out the color of the vacuum lines connected to these two ports and what vacuum motor they run to, since the table on the right side has "defrost" listed twice. However you should measure vacuum at two of the vacuum motors when controls are in the Defrost position.
Bruce
-
Okay trying this again.....
-
Good Afternoon y’all,
I see the diagrams but, i have a couple questions still. My truck doesn’t have vacuum ball installed and currently I dont have the vacuum lines connected to the AC system. First, I need a vacuum ball correct? What vacuum port do I need to use from my Edelbrock carb? Ported or manifold? Having the line that is marked to source on the diagram would go to the vacuum ball and then to the carb? What size vacuum lines needs to be used? Thank again.
-
It will work without the vacuum ball, but the ball is the vacuum reservoir that keeps the vacuum steady. Without the ball, whenever you accelerate the vacuum will drop and all the HVAC doors will go back to the non-vacuum position.
In my truck the ball is a larger cylinder, and it is mounted right next to the HVAC plenum under the hood. There are two vacuum connectors on the bottom.
- One connector has a vacuum line running to the intake manifold vacuum port on the carburetor. It could be connected to either the carb or directly to the intake manifold.
- The second connector has a vacuum line running over to and through the firewall.
The vacuum lines under the dash are GM "hard" plastic vacuum lines, not rubber lines. I think the line through the firewall may also be hard, line but I don't remember for sure. Hard vacuum line will slip inside of a small diameter rubber line, so you can make the transition at any point.
The hard line under the dash runs over to the controls and connects to the vacuum port. All other vacuum lines under the dash are hard lines, with small rubber connectors on each end to connect to the vacuum motors. You could use rubber vacuum line to replace them, but its bigger diameter and harder to route under the dash.
GM 1/8" hard plastic vacuum line used to be available at most good auto parts stores. However, I looked online and didn't get any hits from the typical parts sites.
I think this hose is close, but the original was 5/32" OD and 1/8" ID. https://www.amazon.com/Dorman-Help-47417-Hard-Hose/dp/B0006305N8
This might be the right size, but they don't provide specs. https://www.amazon.com/Dorman-Help-47418-Hard-Hose/dp/B0006305NS
Bruce
-
The 1985 model trucks used a reservoir with only one 7/32" (5.5 mm) vacuum port requiring a check valve to be inserted between the manifold vacuum source and the reservoir (attached image). The 7/32" vacuum supply hose running between the check valve and reservoir was then tee'd to the 1/8" (3 mm) vacuum spaghetti line entering the cabin through the firewall adjacent to the evaporator house. Factory cruise control, when installed, also shared the 7/32" vacuum supply line isolated by the check valve.
Earlier design vacuum reservoirs, such as the type used on 75gmck25's truck, contained an integral check valve, hence had two vacuum ports, one connected directly to the manifold vacuum source and the other to the HVAC system.
-
Thank you, I really appreciate your help. Just to make sure, I have two options. One, I find a 75 year ball and run it from the manifold vacuum on the carb to the ball then thru the firewall. Two, use an 85 ball. From the manifold vacuum lines, run to a check valve to a tee, then the ball. Connect the Tee to the vacuum line that is thru the firewall just left of the distrubutor?
-
Correct.
-
Awesome, thank you! Another project to complete.....