First off, I've been working on repairing a cracked condensate pan in my home air conditioner. I had repaired it about a year ago with epoxy and it eventually failed sometime recently. When I checked, the entire chunk just peeled up off the crack. So, I've been doing some experimenting with different adhesives on a general purpose drain pan I have. I first cleaned it with alcohol, then roughed it up with 180 grit sandpaper, then cleaned it again. I tried JB Waterweld, regular JB Weld, some Loctite plastic bond epoxy, and some Black Jack Neoprene Super Flash Cement. All of the epoxies just pried right off after they had cured. The Waterweld was stuck the tightest, but yielded to a putty knife and came off in one piece. The Black Jack was still pretty sticky after 24 hours and I think that's what I'll go with since it will stay flexible.
Now the rant. Most air conditioning problems I've personally experienced are the fault of the installers. I had a new house in Phoenix and one of the air conditioners kept losing freon from the day we moved in. Turns out a solder joint in the attic was leaking a tiny amount. My son paid over $ for a new, high efficiency air conditioner in his home 4 years ago and it recently stopped working. Apparently the installer had left two freon lines rubbing together in the compressor unit and it eventually wore a hole in one. In fairness, I suppose it could have come from the factory that way, but I'd think the installer would check all the lines to be sure they aren't touching. The crack in my drain pan was caused by the weight of the evaporator coils resting on the pan near the corner where it cracked. The pan is suspended around the edges, not directly under the coil corner so it eventually gave way. I've tried to rectify the problem as well as I could by lifting the coil a bit and using a hefty sheet metal screw through the steel flange on coil side into the framework of the housing, like is done on the other side. Hoping like heck I haven't caused any freon leaks by jostling the coils.
If I do have to replace the condensate pan, I think the coils will lift up far enough to slide the old pan out and slide a new one in, assuming I can find a 24" x 18" replacement. The lines from the coil go off to the side for 4 or 5 feet then make a 90 degree turn to go to the compressor unit.