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Galant A/C Blows Air Intermittently

Over the winter, the A/C in my '04 Mitsubishi Galant quit working. It wouldn’t blow any cold air at all, but I didn’t mind too much since it wasn’t hot out. In preparation for a hot NC summer, I took my car to a dealership about a month and a half ago to have the A/C fixed. They replaced the condenser, and the car started blowing cold air, but it would only do so intermittently. Two weeks later, took the car back into the dealership for them to have a look, but it blew cold air during the entire time that the mechanic was looking at it. I specifically asked about the compressor, but he said that it seemed to be fine. Since then, I’ve been trying to figure out what causes the A/C to stop working. I haven’t been able to find an exact cause, but the A/C will typically blow cold air when the car is not moving or when I am braking. It is also more likely to work if it isn’t hot outside (which isn’t exactly helpful). If I am on the highway, applying the gas, or if it is hot outside, it is much less likely to work. As I am driving, I can hear the A/C click on and off; for example, if I apply the brake, I will hear the A/C click on, and it will blow cold air briefly (around 30sec - 1min or so). To complicate things, recently the A/C has blown fog in addition to cold air. This has happened three times. I’m at a loss for what the issue is… I don’t want to take my car back to the dealership unless I have a good idea of what is wrong because I’m pretty sure that they thought that I was crazy after I brought it in the second time.

Please help! Thank you so much in advance!

I am no AC expert but it sounds like they have too much freon in the system. If idle is ok and slow moving is ok then the pressure is low because the compressor is not turning at “road speed”. When you get moving, the motor is turning faster and the compressor is turning faster so it hits a high pressure limit switch and turns the system off. The frost coming out of the vents also leans towards the evaporator in the dash trying to freeze up like there is too much freon.

When I had the condenser replaced, they also had to recharge the A/C because the condenser had been leaking, so this could make sense. If this is the issue, is the solution as simple has having the pressure / amount of fluid checked?

Are there any other possible explanations for this?

I had a 2001 Galant that I had trouble with the AC on. It was completely different case than what you are describing so I will not get into the details. What I am focusing on is the mechanics that worked on mine would leave it in the shop with the gauges connected while they looked at things. It would not fail in the shaded area of the shop while sitting still. They needed to get out and drive it to see the problem. Maybe you have the same mechanic mentality going on at your dealership where they do not reproduce the problem because the car is stilling still at the shop?

To answer your question though, most places are supposed to weight the amount of freon that goes into an open system to determine if they have installed the correct amount. Two reasons, cost of the freon is high and they do not want to waste money there and the reason you have where an over or under charged system doesn’t preform correctly. So once a system it filled, they use the gauges to determine if the amount of pressure is correct when the compressor is engaged. Just reading the gauges is not as accurate as the weighed amount of freon being installed in a freshly opened system. I believe it would be easy to over estimate what is a good range on the gauges as to what level would trip the high side pressure switch. But that is a pure guess.