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I have installed a Fridge King AC evaporator and fan unit inside my car. Everything else is new.


I am trying to install a relay so that when I turn on the AC fan, it disconnects the heater fan. I am using a 5 pole relay with a Normally closed (for the heater fan) and normally open (for the AC). When power is applied to the relay control circuit, the Normally Closed circuit opens to shut off power to the heater fan and the Normally Open circuit closes to allow power to the AC fan and compressor.


My question is how to hook up the controlling circuit so that the AC fan switch (3 speed) automatically shuts off the heater fan power.


There is a wire from AC fan switch to the temperature controller that only allows the temp controller to start the compressor when the fan is turned on.


I am thinking of connecting both a direct power wire (16 gauge ) and the Normally Open wire (12 gauge) to the power leg into the AC fan switch and then a relay control wire from the leg on the AC fan switch to the temperature controller. 


This means that the AC fan switch power feed would have 2 wires to it. One has power full time (16 gauge wire), and when you turn on the AC fan, it would energize the relay and would shut off power to the heater fan and provide power through the relay to the 2nd wire (12 gauge) to the AC fan switch power feed.


I know, confusing, but does this sound correct? Is there a better way to connect the relay to switch power between the heater fan and the AC fan?





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You don't really need to do this.  I realize that Behr A/C units are wired so that turning on the A/C blower disconnects the heater fan from the car's electrical system.  Frigiking wiring setups don't do this.  It's not gonna hurt anything if you accidentally turn on both blowers simultaneously--although it'll pretty well use all the amps a stock alternator will produce.  


If you really want to do this, I'm sure you could find a double pole, double throw switch that in one direction would energize the heater blower and in the other, the A/C.  My '73 has had a Frigiking unit since it was new, and the few times I've accidentally turned the heater blower on while the A/C was running, nothing bad happened.



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I agree with Mike, above, and would add that the Clardy A/C system, like the Frigiking system, offers no safeguards against operating both systems simultaneously. I have a Clardy system in my ‘76, however, and have used that “feature” to my benefit: if you turn the A/C thermostat all the way down (well... to the warmest temperature) and the A/C blower on, along with the heater blower, you can distribute heat far more effectively than the weak-ass heater alone, partly because you have two large vents facing the passengers. The A/C compressor almost never came on during this process. Great when visiting Rochester in January... 😉


Alternatively, in case you really want to tinker, you could look at the Behr A/C wiring diagram for an example of how a safeguard could be installed. You can find the wiring diagram in the installation manual, PDF’d and available free on the tiiregister website.






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