Join Date: Apr 2006
Thanked 189 Times in 185 Posts
Rep Power: 13
Technically, you need a wet/dry sling hydrometer to measure the relative humidity and temperature (both at the same time) to see how well an AC unit is working. But the air coming off an AC unit, right in the outlet duct, should typically be 45-50F if you stick a thermometer in it. The exact temperature will depend on relative humidity (there are published tables in AC repair guides) and how hot the outside air is, i.e. sometimes you can expect a 40F drop in air temperature, sometimes 30F, depending on the system and the environment.
The odds are that your system has gotten old and lost some of the gas ("Freon") charge due to slow leaks in old age. 15 years is a good long life for an air conditioner, especially in a marine environment.
I'd look for obvious physical problems, i.e. does anything need cleaning? Is the unit getting good power, no wiring problems? Filter really clogged? and if there are none--then it is time to find out what a service call will cost you, to see if it just needs gas, or needs a leak repair, or outright replacement.
Somewhere on the unit it will say what gas type it takes (R22, R12, R134a) and depending on that, it may or may not be feasible to repair.
While DIY repairs to AC are not impossible, doing it right takes a bit of equipment and study, so it can be faster-simpler-cheaper to call in a pro for a one-shot project.