I am not a car guy, I don't even change oils for my cars, but I fixed my van's AC problem!
Last week it was our turn to drive for carpool to early morning marching band practices. On Wednesday morning, while waiting for the last boy to arrive, I noticed that the AC vents at driver side blew warm air even though I did not turn AC on.
That afternoon happened to be hot. When I started the van to go home, I turned on AC for cooling. I felt the blow of warm air from driver side vents again! It was hot, so I gave AC a few minutes to really work. The air got hotter as I drove. It was so hot that I had to open van's windows.
I checked the air from passenger side vents, it was cool as it was supposed to be. Apparently AC was working, something else was not. My snap judgement was 1) hoses leaked, 2) some valves malfunctioned, 3) on board computer malfunction.
Find root cause
I drove to the car service shop near my house and talked to the service adviser about the issue. I described to him what happened, withholding my own diagnosis, and asked him about the potential reasons. He gave me a check list answers to cover everything. So I told him my own diagnosis to try to narrow down the potential reasons, and emphasized that passenger side vents blew normal cold air, and driver side vent blew erroneous hot air. He double checked my van's make/model, and told me that the van has a separate valve for each side of the vents, it was likely that the valve control hot air intake on driver side stuck in open position.
I turned on and off the van a couple times already, it was not likely to be a on-board computer issue. I am pretty sure that the stuck valve was the root cause. I made a reservation for Saturday to fix the AC.
I thought about the situation a bit after I parked the car in the garage, still sitting on the driver's seat:
How do I fix the stuck valve problem physically? I need to wiggle it back and forth.
How do I wiggle the valve without opening the hood? I change AC temperature on the dash board.
I changed the temperature up and down by 10 degrees, not seemed to work. I adjusted temperature setting to both extremes a few times ..... and then set it to cold, the cold air started to blow from driver side vents. I fixed the AC problem without getting my hands dirty!
Be observant, be curious and connecting dots to seek solutions. "Be observant" leads to identification of problems, "Be curious" helps to find root cause of the problems, "Connecting dots" will give you a good solution in short time. This is my default approach to all aspects of life, be it technical or non-technical. This time I used it to fix the van's AC problem.
Of course these all happened subconsciously - I dissected the process to write this post -:) because it was a very satisfying experience!
The only guilt I had was that I forgot to cancel my reservation to fix the AC at the car service.
Note - other similar examples in this blog include fixing Kenmore Washing Machine Lid Switch, Setting Thermostat for Central AC in a Two Story House.