Who knows a thing or two about home HVAC?

Okay, so here's the deal. We had a raging storm here in Maryland, last summer. A power surge hit the house and the AC system hasn't worked right since. I've called two people out to look at it (last year) and got hosed both times. It's going to get warm soon (I hope) and figure maybe I should start working on this now.

Since the storm, the blower does not run at a consistent speed. It speeds up and slows down. That causes the system to freeze up. When it does, I shut it down immediately upon noticing it.

First guy comes out, gives me a 37 second assessment that my system is shot and I need to spend $7500 to replace it. He tells me the refrigerant lines are low, and since it's an R22 system, it's best to replace it. My question to him, umm.....why isn't the compressor running? If the compressor isn't running, isn't it going to look like the refrigerant level is low? Duh! He never did address why the compressor wasn't running. I figured that one out on my own.

It turns out, the compressor wasn't running, because only one leg of a double pole breaker tripped. Reset the breaker, voila, the compressor starts running. The system still freezes up.

Second guy comes out: "Your refrigerant levels are fine, but before we can look at why the blower speeds up and slows down, you need to spend $300 to pressure test your system." Why? "Well to make sure there are no leaks." Umm....if there are leaks, wouldn't the refrigerant level be low? He didn't want to seem to address the problem either and was shown the door.

So, yes the AC system is a bit on the old side. However, it really doesn't get used that much. I have some really tall trees around the house that shade it well so unless it is like 100 degrees outside with 200% humidity, the house actually stays relatively comfortable. Due to my allergies, I don't cheap out on filters, and change 90 day filters about every 30 days. Because of that, when I pulled the covers off the air handler to check the coils, I was surprised to see they were pretty free of nastiness but cleaned them anyways. Still didn't fix the problem.

Where should I start?

Blower motor speeds up and slows down? I'm thinking either blower motor or wiring is shot here. That would be a start, anyway. Speaking of which, start caps OK?

Did they check the pressure without the compressor running? You can't tell anything about it without the compressor running.

Yes the first guy did check without the compressor running - which BEYOND irritated me. He never addressed why it wasn't running.

I use to work for a chiller manufacturer, 12 years ago. But, I worked mainly with absoption chillers, never got into controls, rarely anything under 250 tons, and never dealt with air handlers. So, I don't have any trouble shooting experience but understand a good bit of theory. Combine what knowledge I have with the knowledgeable "pros" I've dealt with and you'll understand why I've decided this is just going to be easier if I fix it myself.

Sounds most probably like the slow fan speed you described. Condensation will freeze on the coil w/ low air flow. Could also be low charge but I'd stick w/ the fan first.

Its no secret, but you need to find an honest HVAC man. Its not the easiest thing to do.

My guy charges me a service call, but he will test the pressure once he gets there and its not $300. I can tell you the price of R22 has gone way up.

What kind of blower do you have?

The reason I ask is that I've got an early-generation ECM (electrically ... something motor) blower in my unit, and they have a controller board both in the air handler, and on the blower motor. Both boards are NLA on my 16 year old unit. Both boards have gone bad.

Since you mention the fan speeding up and slowing down, do you have a variable speed blower, controlled by (one or more) "boards" (for lack of a better term).

You can learn more about them here: http://www.thedealertoolbox.com/index.cfm

I have the diagnostic tool for the early (I think up to Gen2.6) in my basement, which is yours for a couple bucks over shipping if you think you have one of these units, but I'll warn you that parts are pretty much NLA, and any dealers who have them are convinced someone is dying to pay $1000 for their 10 year old blower motor on the shelf.