Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Air conditioning (cold side) functions intermittently

2002 Honda Civic LX

Maybe a year ago I started having problems with air conditioning. The hot air part works fine, no problem whatsoever. But the cold air thing doesn’t work as it used to. It’s not the fan - the fan blows enough air for a little storm, it’s just not cold enough.

First time I noticed, it just stopped making cold air for maybe 15 minutes. Air was coming in at ambient temperature, not even a degree cooler than that. Then it started working again. Ever since then I’ve had intermittent failures like this, and then it would start working again. It’s not a change in flow, it’s a change in temperature.

Second symptom - even when it does work, it seems inconstant. Before, I could just set it and forget. Now sometimes it seems more fidgety, and I have to keep turning the button when it starts acting up.

Third symptom - it doesn’t seem to make any cold air at all when the engine is idle. The engine must run at normal cruise speed to get any cold air out of it. Before, it was slow to make cold air when idle, I had to wait a while, but eventually it would start to make cold air. Nowadays, if I’m coasting downhill, there’s no cold air at all.

I’m worried that one day it will stop working altogether. Plus, it’s not fun when it’s hot outside and this thing decides to take a vacation. I didn’t care about it in winter, because the hot air works fine, but now that summer is knocking at the door, this is suddenly a problem.

What might have gone wrong? Is it something that’s easy to fix at home, or should I take it to the mechanic?

The number one problem with air conditioning is the freon charge gets low due to leaks. You should take it to your mechanic and have them check the charge. If the charge is low then recharge the A/C with leak dye added.

A/C work is not for amateurs. It could be low on charge, but it could also be a system blockage, compressor failure, or a problem with the control module. You need pricey equipment to diagnose the problem. I’d find a good independent mechanic that specializes in auto A/C.

As mentioned, have the state of refrigerant charge of system checked. If the state of charge is fine, then the problem might be with the expansion valve.

The expansion valve is what meters the refrigerant into the evaporator which makes the cold air.

I can’t tell you how many expansion valves I’ve replaced for the problem you describe.


I’m with busted on this. “Bite the bullet” and find a reputable auto AC shop.

Just as an FYI, the heating system and the A/C system are two separate systems in series with (stacked on) one another. The heating system uses the engine’s heated coolant traveling through a small radiator to add heat to the cabin, and the A/C system uses its refrigerant in another small radiator-like device to remove heat form the cabin. The refrigerant is more “processed”, as it has to be compressed, cooled, then allowed to decompress, then compressed and cooled again, but both systems pass the cabin air through a “heat exchanger” to either add or remove heat. And both systems are separate. In some cars they’re both controlled by the same controller, and they both use the same ductwork, but they’re still mechanically separate.