On the first hot day of the year I cross my fingers, hold my breath, and plead, “Please, please, please!”

For the first time after the long Maine winter, I’m about to switch on the air conditioning in my old truck. Rewarded by a blast of cold air, I breathe a frosty sigh of relief.

I’m happy to cool down, and I’m even happier that I don’t have to diagnose and repair my AC system. The folks who built my truck 15 years ago did a good job, and the system is still operating as designed, with all the refrigerant contained in the sealed system.

Judging by the selection of refrigerant top-off kits for sale at parts stores, many car owners aren’t as fortunate as me. As a professional technician, I’m alarmed by the products available for do-it-yourself AC repairs. If you’re already hot and bothered by the temperature, you do not need to frustrate yourself with a failed attempt to restore your AC system performance.

Some car owners make the mistake of adding refrigerant as they would add gas or oil to their cars.  Air conditioning should never need topping off.  If the refrigerant level is low, it is due to a leak and there is damage that needs to be repaired.  Besides safety concerns, there are many problems with using a kit to simply add refrigerant.

First of all, if the original refrigerant leaked out, then the next batch will follow the same path and you’ll be right back to warm AC again. The DIY kits that frighten me the most include goo that is supposed to stop leaks. Instead of repairing the leak, the goo does further damage when it clogs up the system elsewhere.


Also, consider that if refrigerant leaks out of your car, then air and moisture leak in to take its place. Another problem with just topping off the refrigerant is that the contamination hasn’t been removed. Air and moisture don’t have the same properties as refrigerant, so if they are left inside, the system might be cooler after a top off, but it will not be cold.

A final problem with using a top-off kit is knowing how much to add. New-model AC systems are more efficient and contain half the amount of refrigerant as older models. This means there is less room for error when filling a system to the specified capacity.

Too much of a good thing results in the same outcome as too little and the temperature still won’t be cold enough.

Despite the marketing of DIY kits, there are no short cuts to repair a leaking AC system. Professional repair shops invest in trained personnel and precision equipment for detection of leaks, evacuation of contamination, and measurement of refrigerant.

The reason I desperately hope my AC works is because I dread the time and expense required to repair it. But if my springtime hocus-pocus fails to get me cold AC, I would rather fix it right the first time in a professional manner than exacerbate the damage with an aftermarket top-off kit. Summer in Maine is too short for such aggravation.

Ruth Morrison is an Automotive Technology Instructor and Department Chair at Southern Maine Community College.  She holds certification as an ASE Master Technician and Advanced Level Specialist and was a former Ford Senior Master Technician.  She graduated from the Ford ASSET Automotive Technology program at Central Maine Technical College and most recently earned her master’s in Adult Education from the University of Southern Maine.  

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