Should I replace the whole heat pump or just fix the indoor coil?

I was in almost the same spot two winters back with a 17-year-old heat pump. The coil started leaking, the line would ice up on long runs, and the house couldn't keep up on cold nights. I got one quote to swap the coil and one to replace everything, and I cheaped out and did the coil. It worked fine for about two seasons, then the compressor started tripping on overload and the repair guy basially said the compressor was the same age as the coil and living on borrowed time. Ended up paying for the full replacement anyway, just spread over two years instead of one.

That said, it's not a total gamble every time. A neighbor down the street did the same coil swap on an older unit and got a solid six or seven more years out of it. The difference, as far as I can tell, is how hard the system runs and whether the compressor has been struggling along with a low charge for a while. Yours is icing because of the coil, most likely, but if it's been running short on refrigerant for a couple of seasons, the compressor has been working harder than it should that whole time.

One thing I'd ask both techs: what refrigerant does the replacement coil get charged with? If your system is on the old stuff, that alone pushes me toward replacing, because a leak or service call down the road gets expensive fast when the refrigerant is scarce. If the five figures is genuinely not doable this year, the coil swap isn't crazy, especially in a small house with light usage. Just go in knowing it's a coin flip on the compressor, not a guaranteed fix. And if you do replace, ask them to include a labor warranty, not just parts.

We did the coil swap on our old unit about eight years ago and it's still going, for whatever that's worth. The thing that seemed to matter most was the tech who did it. He wouldn't button the system up until he'd pulled a proper vacuum on the lineset with a micron gauge and held it, said the last shop that touched it had left moisture in the lines and that's half of why old coils rot in the first place. Took him an extra hour but the charge has held steady ever since. Maybe ask how whoever does the swap verifies a clean, dry system before they charge it. If they shrug at that, I'd be picking a diferent contractor regardless of which repair you choose.

I don't have a story to add yet, just dealing with the same dilemma at my place so this thread is helpful. One thing I haven't seen asked is wether the repair guy can actualy test the big outdoor unit before you commit either way. Like, can they hook it up, check how hard it's working, and tell you if it's got years left or is on its way out? Seems like that would take some of the coin flip out of it. Is that a real thing they can do, or is it just guesswork once everything's this old?

Before you pick either quote, I'd push back a little on the diagnosis. Icing near the end of a run can point to the coil, sure, but it can just as easily be a blower running slow because of a clogged filter, a failing blower motor, or a duct restriction somewhere, and those are all cheaper to rule out than a coil swap. I'd want a static pressure test on the duct system and a look at the outdoor unit's defrost cycle before anyone sells me a part. If the tech just eyeballed the iced coil and wrote a quote, that quote is built on a guess.

One thing to check before you pay for that coil: ask what warranty comes with it when it's bolted to a 19-year-old outdoor unit. Mine wouldn't get a real parts warranty on the new coil becuase it wasn't matched with the condenser, so if it failed early I was out the whole cost again. Also worth asking both shops to quote a replacement for the shoulder season instead of now. My guy charges less when he's slow in April, and he's not squeezing me in between emergencies either.

Update: took the advice about checking the easy stuff first. Filter was fine but the blower motor is dragging, spinning slower than it should, which explains some of the icing anyway. Getting a quote on that now. For those who swapped coils on old units, did you replace the blower at the same time or separately?