AC_Heater Box Rebuild

Discussion in 'Workshop Forum' started by LarryC, Jan 2, 2013.

  1. LarryC

    LarryC Curator of #10105275

    About the time that I was starting to rebuild the AC system last summer, my AC-Heater blower started to become balky. So that halted my AC project, which I will pick up in my other thread when I finish a re-build of the AC Heater box. It is just as well, since I discovered that the upper flapper on the AC_Heater box had been stuck so I was running a constant blend of external and recirculated air and didn't know it.

    Also, the factory used copious quantities of some sort of tar like gunk to seal the upper housing. This had hardened over the years and eventually started to come apart and drop down into the blower. Hence the strange scrapping and flapping sounds that had begun a few years ago whenever I turned on the heater. Meanwhile the blower motor bearing had started the slow process of seizing and was gradually getting stiffer and stiffer.

    That plus all the leaves, debris, and dirt collected in there over the years meant that a rebuild seemed like a good idea before proceeding with the AC restoration.

    Removal of the box occurred over the last couple of days. As others have said, the process is mostly tedious but not impossible. Definitely more tedious than the master cylinders. I drained the cooling system via the two bolts on the lower coolant tubes under the frunk, and disconnected the heater hose connection at the rear to further drain the heater lines before starting in on the heater hoses at the box. The antifreeze was crystal clear, so no problems there.

    Getting the box out is not too bad once you discover the angles to approach the various screws. Also there is a generous cut-out just forward of the accelerator pedal that you can get a hand through to undo the forwardmost heater hose. A deep socket 10mm is necessary for the four mounting nuts. Then the whole box gets wiggled and guided out the passenger side, stopping repeatedly to guide things past wires and edges.

    I will post images throughout the process starting here with the box as is. Since no one seems to want to post pictures of the box for those who need to do this in the future(!), I will post complete views of all four sides so you can see where everything is located, including the legendary heater valve. Just having a mental picture of the arrangements is worth five shop manuals. Incidentally, the removal described in the shop manual is pretty good.


    The lower housing, showing all the tar-like gunk used to seal the box and the cause of some strange sounds

    The heater blower motor, 79 version
    Last edited: Aug 28, 2017
  2. budgetzagato

    budgetzagato Administrator Moderator

    Olympia, WA USA
    Does not look fun...

    I wonder if the tar stuff is more insulation/vibration dampening than sealant. I've seen weirder stuff done in cars.

    You can probably use some open-cell weatherstripping foam tape around some of those flap doors, that's a common fix for Vanagon heater flaps too.

    Good luck, I look forward to seeing your progress.
    Stoney#1 likes this.
  3. lookforjoe

    lookforjoe True Classic

    Many thanks for the photo-documentation. I'm sure I'll be doing this at some point. Having good pics definitely helps! :)
  4. rachaeljf

    rachaeljf True Classic

    Northampton UK
    Seconded! Thanks Larry, very useful stuff.
  5. lookforjoe

    lookforjoe True Classic

    Where's the other heater core line? I see what must be the feed in through the heater valve, but where is the outlet (or inlet, if its routed with the valve on the return side?
  6. LarryC

    LarryC Curator of #10105275

    Hussein, I had already removed that

    It attaches to the rightmost heater hardline coming out of the tunnel and was in the way for removal of the box. Unlike the other heater core hose it appears it is not a right angle design, so I will hopefully just go back with a standard 5/8 heater hose on that one. The other two, the one for the upper core and the valve inlet I will source from Obert.

    Not much to take pictures of today. I spent most of my shop time just cleaning and scraping the tar-like gunk off the box. I think I got most of it and started in on cleaning and polishing the housing and the AC evaporator. I used a fin comb to straighten out the evaporator fins. I figure that every little bit of improvement in the efficiency I can get will help down the line.

    I will definitely need to find a new upper flapper as the hinge on mine is fused with rust from having apparently been unused for so long. In the meantime I will see what I can do with the motor. It looks to be a totally rebuildable piece and has provisions for disassembly and maybe new bearings.

    I forgot to post up a close-up of the magical heater valve, so I will do that here.
    TheValve copy.jpg

    I am a bit undecided what to do about the valve. It has never given me any trouble, and it appears to be leak free. Now that I now where things are located and that it is removal, and that I have broken the mounting screws free, I think I will leave it alone. I may also replace the rivets holding the flapper door vacuum motor with screws so that it can be replaced without removal of the box.
    Last edited: Aug 28, 2017
  7. Wyverndude

    Wyverndude True Classic

    Silicon Valley, CA
    If it helps any...

    ... I don't think the tar-like sealant is factory. You should be able to just remove it and not worry about replacing it.

    As for the heater valve ... mine rusted through at around 60K miles or so. I replaced it with an all-plastic valve from a VW Rabbit.

    Previous thread here:

    The AC car has the valve integral with the water neck that bolts to the heater core; but it's the same heater core. The non-AC car has two water necks. If you get one of those you can use an inline valve like the VW.
    Last edited by a moderator: Dec 3, 2016
  8. LarryC

    LarryC Curator of #10105275

    Interesting view. But…

    it is almost certainly from the factory since this X has pretty much not left my sight since it rolled off the dealer's lot. Being an early AC you have to wonder if they were experiencing trouble with condensation finding its way past that seam as it dripped down the sides of the box interior. And it was blamed on Mario on the assembly line, who was responsible for sealing the boxes. So Mario just increased the supply of sealant: "You want sealing?! I give you sealing! How is this for sealing [a quarter pound of sealing on each side of the box!!]! None of the AC boxes on Mario's assembly line leaked after that.:dance:

    The heater valve on all the AC boxes that I am aware of are at the back of the box as shown in the late model shop manuals. Interesting if there were some near the heater core.
  9. Wyverndude

    Wyverndude True Classic

    Silicon Valley, CA
    ... at the back of the box

    -Ah, I see what you're saying: Yes, your heater valve is in an entirely different location from mine.

    My car is a 1981, but the A/C is from a different car; and I don't know what year it would have been except that it would NOT have been one of the ones with the extended water pump.

    It's been too long (about 20 years) for me to remember for sure, but it's entirely possible that I transferred over my original (non-A/C) heater core into the A/C box. Apparently it fits...

    If nothing else, this suggests it's a simple thing to do (and then you have a much more available heater core and valve setup) as I don't remember having to jump through any hoops to do it.

    But again, it's seriously been 20+ years, so... :confuse2:

    Either way, it would seem there's the option to get another water neck to replace the water neck/heater valve, which then gets you straight from the heater core to a hose fitting, and then use another inline valve.
  10. LarryC

    LarryC Curator of #10105275

    Continued clean up and restoration

    Continuing with my documentation, here are some details of the AC-Heater box and components that are hard to find pictures of when you need them. Maybe these will help others.

    The heater valve: This is almost never pictured so it is difficult to understand how it is fitted. It is a RANCO h111. Ranco has been around a long time and supplied heater valves for a lot of GM, Mopar, and other makes over many decades. There are many valve out there that are similar, including the Ferrari 308 heater valve which is almost identical, but cost four times as much..



    AC Evaporator, top

    AC evaporator, bottom

    heater box, top

    heater box top, underside showing where the AC evaporator attaches
    inside_upper_housing copy.jpg

    heater box, middle housing
    middle_housing copy.jpg

    heater boc, lower housing
    lower_housing copy.jpg
    Last edited: Aug 28, 2017
  11. ng_randolph

    ng_randolph Bjorn H

    SF Bay area
    Great thread, thanks for posting!

    Here is the Ferrari part on eBay, buy it now at $175. There is also a "RANCO VINTAGE UNIVERSAL HEATER CONTROL VALVE 5/8 " X 2 HOSE NEW" with a buy it now of $33.50, looks identical to the Ferrari part. Perhaps the universal part can be made to fit the X1/9?
    Last edited: Sep 1, 2013
  12. PaulD

    PaulD Paul Davock

    Kitchener, Ontario
    I just ordered a Ranco universal

    I will report back on how it compares to the original when I receive it.

    Currently I am using one of these:

    Even it is the same, it will likely be a while before I pull out the heater box to revert to the original set up. Perhaps getting the AC heater box out would be easier the second time, but...

    Paul Davock

    Paul Davock
  13. hiram6

    hiram6 Obi Wan Kenobi

    Lawrenceville GA
    Larry, thanks for picking up the ball on this, my apologies to all for not providing more details in the other thread we had going back in December on this topic. We (the wife and I) just got back into town after 4 weeks away from home, so this is my first time online in almost a month.

    After dealing my Dad's illness right before Xmas, we left for an extended vacation in a seriously off-the-grid location. Hint: Pacific Ocean out our front window, howler monkeys in the backyard.:nana:
  14. LarryC

    LarryC Curator of #10105275

    Continuing with the AC-Heater Box Rebuild…

    After much labor (!), I managed to get the fresh air flap cleaned up and painted
    To prevent water from collecting in the crimped hinge area I injected some light grease then seal the water entry point with some metal tape.
    fresh_air_hinge copy.jpg

    Then I sealed the closure area on the edges of the flap.
    fresh_air_seal copy.jpg

    There is a connector between the recirculating air and fresh air doors that needs to be adjusted such that the fresh air door closes when the recirculating air door is open. Here's a view inside the top showing the location of the connection and a close-up of the connector arrangement.
    fresh_air_recirc_connect copy.jpg

    air_door_adjust copy.jpg

    Then I did a quick test by applying vacuum to the door control vacuum motor. This is what the doors look like with no vacuum applied, which is where they are positioned when the heater button is pushed in or in normal AC mode. No Vacuum is applied to the control motor.
    fresh_air_closed copy.jpg

    And with the heater button off or in Max AC mode. Vacuum is applied to the control motor.
    fresh_air_open copy.jpg

    The AC evaporator cleaned and mounted to the upper box shell. Note that I sealed the area around the refrigerant lines to prevent water from dripping out during AC operation.
    evap_mounted copy.jpg

    I am still waiting for my rebuilt blower motor to arrive. But once that is here, things will start moving forward again.
    Last edited: Sep 3, 2017
  15. bbrown

    bbrown Bob Brown Moderator

    New Hampshire
    looking good Larry

    I'm impressed on how clean you got the heat exchanger. :thumbsup:
  16. LarryC

    LarryC Curator of #10105275

    Bob, a little vinegar and a plastic bristle brush

    and the evaporator cleaned up nicely. This was more than I had expected to accomplish given that the temperature here was 3 degrees american this morning. It took until noon for the garage to warm up enough that I could work in there! Hence the kitchen counter shots.
    The only other thing I accomplished was a cleaning of the heater core.
    Heater_core_2 copy.jpg

    This is an impressive piece. It appears to be a parallel flow type of exchanger similar to modern condensers (like the one I have installed for the 134 conversion). Super efficient. Plus the fins appear to be copper, too. Which explains why the heater has always been so effective. It also explains why the heater core fins always looked brown.
    Check out the shine on these fins.
    Heater_core copy.jpg

    While I was working on the evaporator I also measured it carefully. It has a volume of 128 cubic inches. This number will be important when I pick up the AC thread again and I show why I got the condenser I did.
    Last edited: Sep 3, 2017
  17. LarryC

    LarryC Curator of #10105275

    Finally had a few more hours in the garage

    The rebuilt blower motor arrived and tested out excellent. I installed new foam strips around the heater core and mounted it and the motor to the lower case.
    lower_assembly_rear copy.jpg

    Lower_assemby copy.jpg

    Then I installed the completely cleaned up middle shell. To keep the air flowing through the fins of the evaporator I made up a new evaporator gasket. This is the rough dimension of the gasket, made from 1/4 to 3/8 foam.
    evaporator_gasket copy.jpg

    And the gasket installed and ready for the upper shell with already mounted condenser.

    And then assembled the upper to the stack for a completely restore AC-Heater box!.

    completed_front copy.jpg

    completed_left copy.jpg

    completed_right copy.jpg

    In the next garage session I hope to install the whole thing and get back to the AC system completion.
    Last edited: Sep 3, 2017
  18. budgetzagato

    budgetzagato Administrator Moderator

    Olympia, WA USA
    Looks great...

    I hope it goes together easily. Nice attention to detail.:italia:
  19. PaulD

    PaulD Paul Davock

    Kitchener, Ontario
    Received a Renco AC heater valve

    The bottom valve is the AC heater valve from Israel sold on ebay:



    As you can see it is smaller. The tubes are about 0.1 inches smaller than the original, and likely prone to leaking with the larger hoses in the x heater system. I guess it would be possible to put heat shrink tubing over them to make a better fit, but the heater box would have to come out again if it leaked.

    With a 0.2 inch spacer it could be made to fit the holder plate on the X heater box.

    It seems well constructed, made of brass instead of plastic and has a nylon support for the rubber washer in the valve. It operates smoothly.

    I do not think will use it though, it was bad enough when the first one gave up, and if heater hose connection leaks I will have done it twice more. The alternative on the passenger side of the box is working, I will stick with it.

    Paul Davock
  20. LarryC

    LarryC Curator of #10105275

    Started installing the box.

    I finally got a few more hours here and there to install the box.

    I can categorically say that installation of the AC-Heater box is, as has been said here before, the worst X-1/9 maintenance item . It took me two and one-half days to get the box mounted. The hoses, cable, and the water valve connections are trivial technical issues. Getting the box to line up that last centimeter is the issue.

    I installed and removed the box three times in an attempt to find out what was keeping it from settling into that last centimeter. Unlike the master cylinder, there is no visibility for the heater box. It's all done by feel. Finally it settled into place today. I have absolutely no idea what made the difference since I tried all the tricks learned over several decades of dealing with this sort of thing.

    Now all I have to do is re-install the console and switches, refill with antifreeze, and hopefully have a clean freshly restored AC-Heater box.....and get back to the AC system restoration.

    My arms ache, my legs ache, and my knees ache. Wow.

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