Introduction: Wiring My Car Air Conditioner for MAXIMUM Cooling!

The air conditioning system in my 1999 civic is in great shape EXCEPT the OEM controller cycles the compressor a bit too often (not rapidly in the cases of low or high refrigerant pressures). I live in a hot climate and AC compressors should not be cycling often. They should be ON more often than OFF. Time to fix this crap.

In the page of the honda civic manual I highlighted the two wires in red ovals. These I will need to connect to 0 volts to engage the AC Compressor Clutch and the AC Condenser Fan. The honda OEM temperature controller will be removed in this mod. I just want simple on off control by the flick of a switch.

Step 1: Time Delay Relay Plus Control Relays.

I needed an ON delay timer to prevent the compressor clutch and condenser fan from engaging when the engine is starting.

This timer from is what I used to give me a ten second delay for my purpose.

I used two relays from an 8 relay card to provide that ground connection to the clutch and fan separately. To activate each relay, the respective inputs on the relay card has to be tied to 0Volt.

Step 2: Providing a Replacement for the OEM Controls.

Since I had previously removed the recirculate and mode control motors from my car ventilation system (since I always use recirculate and don't care for cold air on my feet), I wanted the OEM controller out since it was doing a poor job of controlling the air conditioner.

I used a spare toggle switch and a length of cat5e wire pairs to control my two relays. The other wires in the harness were used for the potentiometer with my pwm controller for the AC blower motor. I used Evo stick to secure the switch to my dashboard console below the deck where the oem AC button used to be.

Step 3: Completion and Testing.

I am now using my glove box as the staging area for my car automation project. I wired the delay ON relay, control relays, power terminal block plus wiring harness in that area.

To fill the voids left by the removed OEM controls, I cut and glued foam pieces into the console. At least the wife wont complain about the "pretty" factor" for this intermediate car mod. Final phase of this project is the car automation pc.

Now the AC works amazingly well. In the second pic you can see the Temperature of the vents (6 Celsius). The air from the dash vents are freezing cold even on the hottest days and I'm extremely pleased. No more 1 minute ON, 15 seconds OFF cycling and hence extra wear/tear on the AC compressor clutch. Once the car cabin is cold enough, I simply flick the AC switch off. In fact this is how I have always used the AC even with the OEM controller for the past 12 years.

If you live in a hot climate and wonder why your car does not cool well, this mod may work for you. Please make sure your refrigerant pressures, compressor, condenser fan etc are all working perfectly before doing this mod.