Need help vacuum line
 

Hi, I have a 1970 C-10 402 w/ AC and I found a small (3/16?) vacuum line that was pushed on the threads of a sheet metal screw on the AC housing. See attached photo. Red arrow is the vacuum line that was pushed on the screw. The aqua circle shows where the vacuum line originates.

Can someone tell me where this vacuum line ( red arrow) should attach? Does the set up of the vacuum lines from the firewall look correct?

Thanks for any help.

Re: Need help vacuum line
 

It goes to your heater valve.

But it seems that you have a manual shut off valve.

That would need to be replaced with the vacuum type if you want to plug in that vacuum line.

See pic.

Re: Need help vacuum line
 

Thanks! I'll pick up a heater valve and replace that manual one.

Re: Need help vacuum line
 

I just plugged my loose vacuum line to the same source today. Prior owner made mine manual with placing an in-line valve in that heater hose.

Re: Need help vacuum line
 

What is the benefit if using a "manual" valve versus the stock valve? What does it do? Original owner of my truck was in AZ and now I'm in WI. Should I swap out manual for the stock heater valve?

Re: Need help vacuum line
 

The Manuel shut will stop water flow into the heater core.

Some say that the heated water in the heater core will cause the cab to heat up.

Once the heater core is full of hot water and you turn on the A/C the vacuum valve will stop the flow of water and the water that is in the heater core will need to cool down before A/C gets cold.

I live in AZ and drive my BB C-20 with A/C and vacuum valve and it’s very cold even in summer.

I have no issues but if I didn’t drive my truck all year round i mite want to have Manuel shut off so as to not have any water sitting in my heater core all winter.

Re: Need help vacuum line
 

Thanks Rods. Good info.