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Thread: Vacuum lines to mode switch and to heater valve. Location and routing?

  1. #1
    Join Date:  Jun 2017

    Posts:    53

    Vacuum lines to mode switch and to heater valve. Location and routing?

    Hey guys, trying to sort out the routing of these 2 vacuum lines but could use some clarification.

    Regarding the heater core valve, a member here posted a youtube video showing that the vacuum line to the valve is the black line that comes out of the lh pontoon in the engine bay. But according to the parts/service manual, the line to the heater valve looks like it should be coming from a tee between the mode switch and the recirc door (I am unsure if the heater core valve is is NO or NC, but I am guessing it's NO and switching it to recirc closes the heater valve for max A/c?). I was also under the impression that the heater valve vacuum line runs up the tunnel (from the aforementioned tee, to the valve).

    So I guess my question for that line is, does it somehow snake back into the lh pontoon near the reservoir (from under the dash) and exit into the engine bay? Seems odd to me.

    I would have guessed, going by the diagram, that the black line exiting into the engine bay right beside the vacuum reservoir was the line going to the mode switch (From a tee, right at the vacuum reservoir), but if that is the case, how does it get back to the interior and to the mode switch after entering the engine bay?

    Sorry guys, only have the parts diagram, service manual, and the odd archived post to try to decipher this from.


  2. #2
    Senior Member Rich's Avatar
    Join Date:  May 2011

    Location:  San Francisco Bay Area, Calif.

    Posts:    2,065

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    It?s all explained in this thread.
    March '81, 5-speed, black interior

  3. #3
    Join Date:  Jun 2017

    Posts:    53

    Hi Rich, thanks for the reply. Maybe you linked the wrong thread, that one is just someone asking what the water valve does?


  4. #4
    Join Date:  Jun 2017

    Posts:    53

    Thanks guys, got my answer (difficult when the car comes in boxes with nothing to compare to).

    Thanks again.

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