Heater, Hoses, and Vacuum testing

[mpierce9]

Hello, I have a 1975 K5 Blazer with Air Conditioning.

I would like to test my vacuum lines in my heater setup.


I get zero heat from my heater after driving my car 30+ miles. This is the position I set my heater controls while I'm getting cold air through my vents.



Here's a recap of what has been done:

1. Water pump replaced
2. Heater core flushed including inbound and outbound heater core hoses
3. Entire cooling system flush (after heater core flush)
4. Cooling System "Burped"

As I move through the different sections here, Off, Vent, Heater and Defrost, air comes through the different areas of the duct system or turns off completely when in the Off position. There is no change with the other positions (A/C or BI-Level)


Here is a current state of the hoses after the car is "warm". Notes are in the image, but just in case. The upper hose is 3/4" and delivering from the water pump to the heater core. The lower hose is 5/8" and delivering from the heater core to the radiator. I have an additional note in the image about a black piece of equipment, if you happen to know what that is.



Inside the cab, both above the transmission hump and behind the glove box are small pancake vacuum actuators. I would like to test these. See image below. I also understand there is another one nested deep in the bowels near the heater core.

A secondary note about the image below. The pancake on the right side of the image opens a port to the exterior of the truck. I can push it open with my hand. I have never seen this actually do anything when changing the different positions of the control panel. I'm not sure if i should be able to witness this change when I adjust the control panel positions or not, but I feel like I should. This is the cornerstone of why i want to test this vacuum system.


After flushing the heater core with no issues and running the system with no leaks I feel good about the state of the heater core.

Everything I've read mentions that taking the heater core section apart is a bear of a job. If I need parts that i have to order online i'd like to go ahead and order them all and be done with it.

If you have any other insight on parts that would be good to order, how to pre-test to see what's working or other general advise I would be very thankful for it.

I've read up on these links



http://67-72chevytrucks.com/vboard/s...d.php?t=463885
http://67-72chevytrucks.com/vboard/s...=397868&page=4
http://forum.73-87chevytrucks.com/sm...p?topic=1949.0
http://coloradok5.com/heatercore.shtml