Jump to content
  • Chillin' Louie (Part VIII: Wiring)

    With all the major components installed and the hoses made, the next task was wiring the system up. This will be a short one (that's not an electrical joke :^), as in a car like this, the wiring is trivial.


    Wiring diagram


    Someone (Conserv, probably) had posted a copy of the Clardy wiring diagram. It is below.





    More general, and probably more useful, is the diagram I have in my a/c book:


    AC_Diagram_Electrical.jpg Generic wiring diagram from Just Needs a Recharge: The Hack Mechanic Guide to Vintage Air Conditioning. All rights reserved.


    The main things to note here are that:

    • The wiring between the fan speed switch, fan speed resistor, and blower fan are part of whatever system you're using, and are not generic.
    • The blower fan switch gets power though the fuse box. 
    • It then sends power to the temperature switch as well as to the compressor (well, to the pressure switch on the drier, which then sends it to the compressor).
    • The big fan on the condenser, however, is controlled by a relay so the non-trivial current from the big fan (typically 10 amps and more) are not running through the console.


    Alert readers will note that, if you believe the Clardy wiring diagram, there's a difference in the way it is wired as compared with what's shown in my generic diagram. In my diagram, the condenser fan relay is sent the "turn on" signal by the blower switch regardless of whether the temperature control is telling the compressor to turn on or not. In the Clardy diagram, the compressor and the condenser fan are turned on together by the temperature switch. If the evaporator core never gets cold enough that the temperature switch shuts it off to prevent it from freezing, then there's no difference. But if it does—if the temperature switch cycles the compressor off—it'll also cycle the condenser fan off, which, if you're in traffic, will prevent the condenser from dumping the residual heat from the refrigerant that's in it. For now, I wired mine the Clardy way. If I don't like it, I'll change it.


    Connection of blower to fuse box

    You can do this a number of ways, such as wiring it to the ignition switch or to the auxiliary pigtail on the hazard switch, but I like wiring anything with an electric motor directly to the fuse box. I used fuse #10, which is the rear window defroster, because a) it's a 16 amp circuit, and b) I assume I'll never need both of them on at the same time. I used a 12-gauge wire, which is overkill, but it's what I had. I snaked it through the grommet for the main part of the wiring harness near the steering column, and up and under the fuse box.


    IMG_6563.JPG Running the wire up under the fuse box...
    IMG_6564.JPG ...and connecting it. Make sure to verify which tab is actually on the fused side of the fuse as opposed to the input side (that is, the blower shouldn't work with the fuse removed).


    For the battery connection, normally I would've made a new one, but the Clardy system I purchased came with its original ring terminal and in-line fuse, and there's a certain emotional appeal in reusing things like this.


    IMG_6831.JPG It's not how I would've made it, but it did come with the system.


    For the relay, virtually any single pole single throw relay will work, but I found this old Hella one I had kicking around the garage, so having it up on the inner fender wall next to the original Hella horn relay is how it would've looked in the 1980s if you'd installed driving lights on the car's bumper.  (I actually have the original relay that came with the Clardy system, but owing to Clardy being an American company, it's a big American relay without the German DIN 30-87-86-85 numbers on the terminals. I thought the Hella relay was more in keeping with the DNA of the car :^)


    If I photographed the bottom of the relay, you'd see that:

    • The blue wire coming through the firewall from the fan speed switch goes to 86. It is also connected via a piggyback spade connector to the other blue wire, which goes to the compressor, following the Clardy wiring diagram of having the same wire turn on both the compressor and the condenser fan.
    • The thin black wire connected to the ground screw goes to 85. (It looks like it's connected to the piggyback spade. It's not. It's just the angle of the photo.)
    • The thick black wire from the fuse holder connected to the battery goes to 30.
    • The thick red wire connected to the condenser fan's positive terminal goes to 87.
    • The condenser fan's ground wire is grounded in the nose.


    IMG_6832.JPG The Hella relay looks right at home. At least it does to me.

    So, as with any other relay, terminal 87 is the12V signal to switch on the relay. Terminal 86 is ground. When 87 (supplied by the clutch wire) is hot, it powers the electromagnet in the relay, which pulls contacts 30 and 87 closed. 30 is connected directly to the battery via the external fuse and 87 is connected to the condenser fan. Whoosh!


    I'm not using a pressure switch on the receiver-drier. I've gotten away from using them in recent years. They're supposed to cut off the compressor if the pressure is too high, as it can be if there's a clogged expansion valve, but I've had too many of them leak.


    That's it. Pretty simple.


    (Next installment: I button it all up, and it gets cold :^)




    (My a/c book Just Needs a Recharge: The Hack Mechanic Guide to Vintage Air Conditioning can be purchased here on Amazon, or personally-inscribed copies of it and my other books can be purchased directly from me here.)






    Was it helpful?



    User Feedback

    Recommended Comments

    As an additional consideration, I also ran an override switch for the compressor so I can manually turn on the cooling fan without engaging the compressor, great for stop and go traffic 



    • Like 1
    Link to comment
    Share on other sites

    Hi Rob, Richard here, would you happen to have the Prosperos Garage wiring diagram for a 72, the one that is supplied on the front page here, the file that is suppiied by IE says it is for a 73 and on up ? thank you, Richard

    Link to comment
    Share on other sites

    Create an account or sign in to comment

    You need to be a member in order to leave a comment

    Create an account

    Sign up for a new account in our community. It's easy!

    Register a new account

    Sign in

    Already have an account? Sign in here.

    Sign In Now
  • Books by The Hack Mechanic

  • Create New...