Simple Tip to Improve a Car's Air Conditioning Performance.





Introduction: Simple Tip to Improve a Car's Air Conditioning Performance.

About: Update 12 September 2017: A very special thanks to Sam Elder, a manager here at Instructables, who tracked down the cause of my lost publications and fixed the issue. Take a bow Sam!

Ever notice on all cars there is a temperature setting? What this does is control the on time for the AC compressor and also the flow of hot engine coolant into the heater core located in the dash.

An interesting fact of thermal flow is that even with the temperature set at the lowest and the flow valve closed, due to conduction there will be heat Leeching into the heater core.

For those of us living in hot climates and never use the heat function, this thermal fact is basically reducing the efficiency of the car air conditioning system.

This an after-the-fact instructable and my car has been running very well in this configuration since 2006. Here is how I helped out my car's air conditioning!

Step 1: Locating the Heater Hoses in the Engine Bay.

It's easy To find by just watching the heater hose connections at the firewall. I deemed these are unnecessary and removed all.

Step 2: Capping Those Heater Hose Ports.

I used size 15 rubber caps with hose clamps to close off all heater hose ports. It's important to monitor these every 6 months or so to check for swelling, cracks and softness. Replace immediately should these symptoms appear. Don't worry the caps are cheap and I actually stockpile a dozen in my trunk tool bag.

Step 3: Completed Works!

Without those hoses the engine bay is less cluttered and has better air flow (like if that matters). The air conditioning system however is significantly colder!

Again don't do this is you need the heater but I recommend for hot only climates!



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    21 Discussions

    I've been an A.S.E. mechanic in my 47th year of service and anyone considering this mod should read the "Service Manual"(not the owners manual) for the vehicle first as since the 1970's vehicles have blended a-c to the windshield defrost cycle to dry up the moisture on the inside. "My a-c runs in the winter time " is a fact -not a problem. Then opposite occurs in summer for adequate engine cooling. The E.C.M. blends hot water into the heater core while the a-c is operating.

    1 reply

    Wow... I would care if I lived in a climate with winter summer and all that sugar candy stuff.

    Hello. I understand what you mean, as I have felt heat coming out the vents during winter, even with the dial all the way to cold/blue (AC off). So yes, heat does get into the core even when it's not asked to be there.

    One warning though about bypassing the heater core in extreme hot climates, and why I advise against it: If your car overheats you can save your head gasket by shedding heat using the heater!

    Some cars do this by themselves (my Audi for example). I've been stuck in traffic on hot tarmac in Dubai's 50+C weather (in the shade!) and my car went from AC blowing cold, to full heat because the engine was overheating.

    If your car does not have the automatic feature, when your engine overheats, flipping to full heat and opening the windows will help save your engine.

    Hope this helps


    I simply added a ball valve on the outlet side of the water pump that went to the heater core. A simple 90 Degree turn and flow was shut off from the core when I wanted it off.

    4 replies

    Via thermal conduction, heat will leech into the car cabin. Complete removal is the best way to stop that. Of course don't do this in cold climates.

    Couple you please explain what and how you did this? sounds like something I need to do to my AC system

    That would be an ideal alternative if you live in a climate where you do need the heater sometimes. Even in some desert climates there are times of the year when it's quite chilly at night.

    whats the function of the expansion valve ?

    Pick up a heater core for an older vehicle and mount it somewhere it will get air flow.

    1 reply

    Guys, you are free to create your own instructable on this extra heater core. My instructable is closed.


    3 years ago

    You could connect the two hoses to an auxiliary cooler for extra engine cooling during hot weather.

    I've grew up in the California desert and now live in South Texas. There are probably close to 75 days per year when I absolutely rely on having the AC on along with the heat. For example the past few weeks it's been raining and the humidity is awful but the outside temp might be in the low 70s. I'll set the AC to LO at first and then raise it to 72. Bringing in heat to the AC improves the systems ability to remove humidity from the air and make it more comfortable. In the summer when the car is hot I'll set it to LO and keep it there no matter what the humidity is.

    2 replies

    On modern vehciles the ac actually runs with the defroster to remove the humity inside the cabin.

    For hot climates we never use the Defroster but in colder ones, yeah I guess.

    Plugging the heater core is fine. On the engine side you really need to loop (small piece of hose from the outlet to the inlet) the hose. On some makes plugging them might be fine but others the pressure can build and cause damage to the cooling system (some jeeps and fords come to mind).

    1 reply

    Not my civic. Been plugged like that for over 8 years.