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A/C leak sealer?

Do any of these products really work or will they just cause more problems?

For a major leak it will not help. For a minor leak and depending on where it’s at there’s a chance it may help to some degree.

If your A/C system is at the point where it’s losing most of the refrigerant charge in a few weeks then it would be a waste of time.

What year/make of car and how many miles on it?

99 Honda Civic. So losing refrigerant in a matter of weeks would be considered a major leak?

Yes, losing refrigerant charge (enough to have it stop working) in a few weeks is a major leak. Don’t wait until there is no refrigerant left because an AC shop can track the leak as long as there’s a little refrigerant left. Then you can determine whether it’s a hose or seal (cheap), a condenser (not so cheap, but more likely), a compressor (more expensive), or an evaporator (probably the worst due to labor charges).

An A/C system is sealed and never loses freon unless there’s a problem.

A leak detector would be best so as to properly find & repair any leak.

It may stop a very minor leak if it’s a seal that’s leaking, but you run the risk of gumming up the system and any sensors. I would avoid it and get the leak fixed properly unless you’re getting rid of the car in a year or so anyway.

I’ve been told that this type of leak sealer usually only lasts about a year. I’ve also been told this can cause significant damage to the a/c system.

I’ve actually used this stuff in some of my older cars that suffered a small leak (say a can a year) and it actually worked to some degree by cutting that can a year down to say a 1/3 of a can per year. There were no problems as far as clogging anything or damage to the system.

That being said, if you’re losing a can every couple of weeks then it’s a major leak and any goop em’ will not help much if at all.
With a major leak like that it should not be hard to find. Look for a dirty oil blotch on the compressor, lines, condenser, etc. That will be where the leak is at.