I drive an old Mercury Marquis as my work car. It's a 2001 and I like it because it's dependable, it's comfortable, and it's paid for. Also, I bought it right and it barely has 100,000 miles on the odometer.
A quick diagnostic told me that the A/C compressor was working, but the blower wasn't working. All the fuses were good. So, I went to Google and learned that there are just exactly two problems that might occur when the blower quits. 1) either the blower has crapped out, or 2) something called the resistor has crapped out. They're both found in the engine compartment.
So, I did what anyone whose son is an SAE mechanic would do. I called the boy and told him that this afternoon I needed him to diagnose the problem. He came over today and in just a few minutes told me that the problem was the resistor. So, we moved a couple of hoses, prepared to take off the resistor, and the blower started working. My son did some more diagnostics and re-installed everything.
Evidently, the problem was an intermittent ground. If electronics don't have a good ground, nothing works, and one of the mounting screws must have gotten rusty, or something, in the 15 years since Ford pushed this one out the back of the factory. It's working now, and I'm thrilled. My son tells me that it'll either quit in the next week or so, or it will work until the wheels fall off and I have it towed to the scrap yard. If it quits next week, I'll go buy a resistor and call him.
But, right now the A/C works and that's what I called him for. Thanks, Matt. I appreciate it.