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Heater box "Source" vacume connection. Where to?

sixsixvette

sixsixvette

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1969 GTX with AC. Need help finding connection point for vacume line. Line 6 from the control connector is listed in book as "Source". Im guessing that it needs to connect somehow to the vacume canister in engine bay. But how does it get routed there?

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this is my 70 dont know if it helps any. Are you asking were does it come out of the firewall?

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Thanks. Checked out service manual and it did not seem to give specifics on getting through firewall. The pics above seem to show it coming through the control valve firewall mount. My valve does not have that style (see my pic below). The service manual does call out a hole next to the bottom screw on the fan motor (see pic below), but I don't see any way of getting the vacume line into that area of the heater box to utilize that hole. Yes, I could hack up my firewall and make a new hole, but want to do it as the factory did.

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20250607_202907.jpg
 
Yep. Im going to add some aftermarket temp, oil pressure gauges and use the same grommet.
 
davek said:
this is my 70 dont know if it helps any. Are you asking were does it come out of the firewall?

View attachment 1864921

View attachment 1864922

View attachment 1864924
Click to expand...
The valve assembly, shown in the pix with the diagram assembly shown, directly below the ballast resistor is part of the A/C Automatic temp control system. The first pix shows the heater core water in/out connection, the second pix shows the blend temperature control valve assembly with the diaphragm assy getting it's signal from the Heater-A/C operators push button on the dashboard and the 3rd pix shows the evaporator inlet/outlet connections below the voltage regulator connectors. The blend valve maintains the interior air temp settings to the passenger compartment........just my interpretation.......
BOB RENTON
 
sixsixvette said:
1969 GTX with AC. Need help finding connection point for vacume line. Line 6 from the control connector is listed in book as "Source". Im guessing that it needs to connect somehow to the vacume canister in engine bay. But how does it get routed there?

View attachment 1864642

View attachment 1864643
Click to expand...

The source for the vacuum line to the number 6 port is engine vacuum. For a 1969 B-body, and A-body, the hose connects directly to a fitting on the intake manifold. The following image shows the fitting for manual brakes and power brakes:
PXL_20250619_000241080.jpg


1969 B-bodies were not originally equipped with vacuum reservoirs. C-bodies with standard air conditioning were equipped with one vacuum reservoir. C-bodies and D-bodies with Auto-Temp air conditioning had two reservoirs. B-bodies with air conditioning received vacuum reservoirs in 1970.

The vacuum line to the number 6 port is routed through the firewall in a molded grommet as shown in the following image (highlighted with yellow marks):
Screenshot 2025-06-18 8.49.23 PM.png

The 1970 grommet has two vacuum lines. The second vacuum line was added for additional control of the water valve actuator.



If your car does have a Chrysler vacuum reservoir, possibly from a C-body, route from the firewall connection and engine fitting as needed to connect as shown in the following image:
Screenshot 2025-06-18 9.08.07 PM.png




If the reservoir uses a single port connect a shown in the following image:
Screenshot 2025-06-18 9.06.45 PM.png



If your car has the metal reservoir used on some 1970 models connect the vacuum lines in a similar manner.
 
Vaanth said:
The source for the vacuum line to the number 6 port is engine vacuum. For a 1969 B-body, and A-body, the hose connects directly to a fitting on the intake manifold. The following image shows the fitting for manual brakes and power brakes:
View attachment 1871518

1969 B-bodies were not originally equipped with vacuum reservoirs. C-bodies with standard air conditioning were equipped with one vacuum reservoir. C-bodies and D-bodies with Auto-Temp air conditioning had two reservoirs. B-bodies with air conditioning received vacuum reservoirs in 1970.

The vacuum line to the number 6 port is routed through the firewall in a molded grommet as shown in the following image (highlighted with yellow marks):
View attachment 1871517
The 1970 grommet has two vacuum lines. The second vacuum line was added for additional control of the water valve actuator……
Click to expand...
This was very helpful!!! Thank you for taking the time to document such a detailed response.
 
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