I have an 036 unit that is about 7 years old. It runs, but the A/C is not cold. I see some moisture on the up-tube, might be oil. do I have a leak? what might be my problem

old old old car.38 years later.

when did it last run good, last week , last yea,r last decade/?
fast idle is vacuum leak, or bad IAC. 1500rpm cold is normal not 3000
overheating has many causes. (huge) need a list or just wan to buy tools to test it and find it.> ???
gue$$ing is hard, work and a real slog. hear goes 1 slog1.
due to age here is the list (a test each)

running 38 year old antifreeze? Lol ?
38 year old thermostat? 7 years is design life EOL ,oops.

engine compression test passes? 180-PSI? wot done?
rad and engine block flushed out of red rust mud.
38 year old water pump is no good nor is the belt. now.

RaD LEAK DOWN TEST, A TOOL; PASS OR FAIL.?
RAD , gas test (exh) a tool that see exhaust fumes in the RAD coolant, green/blue tester all shops have all this here. I typed.

water leaks anywhere under car or passenger toes. , not the side tank blow out you told and is clear
see milk-chocolate for oil in pan, oops leaks. coolant.
see milk-chocolate in tranny pan (did sticked , oops)
Rad CAP must be replaced this old. the rubber gasket in it is dead.
next is see oil or carbon dust in the RAD neck cap off dead cold engine. and full to the top of said neck. (free test eyeballs)

ok all is good above and does it overheat only parked or driven or both or only AC on. or all the above, I bet yes all.
if overheats parked, the fans must all be good are they.?

If still overheats we use IR gun tool and run the beam ever every inch of RAD TUBES. and must show 50f degree variance or more
per tube end to end if not that TUBE is clogged up, RAD BAD./
that is all for now I can do more. if need be..

on simple cause is not checking RAD water level dead cold engine
and making sure that side spill tanks has good tubes inside and work (as engine cools it sucks back coolant.) if tubes bad fix them
or check coolant like 1929 days,RAD cap off. look cold.
Coolant expands naturally hot. that side tank captures it for next cool down cycle and bad rad caps to wreck this cycle.
full stop fingers tired.

pretend caddy here,,, funny then and Diane Keaton hot .(x100)

the bug only needs a fan belt to stay cool.... (owned 2, 1970 to now)

https://youtu.be/Xo2kSu6O8cU?t=2

keep cool.
the side tank blow outs are also warped heads and or bad headgasets
if you see STEAM at tail pipe end hot engine the head gaskets are bad. 1 or both. or far worse crack block.or cracked heads.
id have looked at the tail first. (steam in front yes, look in rear)

Excessive air pressure...if your safety valve is truely popping off, is caused by a bad pressure switch or a loose wire connection at the switch. It's a little odd to be leaking too. There is a couple a possibilities here. The most common spots for leakage is the "tube seal", the aluminum transfer/supply tube, or the outlet air hose. Usually a leak will keep a unit from acheiving full pressure causing the unit ot run continuously. The other common leakage spot is the "check valve" and a leak here usually makes the auto restart (upon using air from the tank, taking pressure below the set lower limit), not work,stalling the motor and popping a breaker. See ereplacementparts for a proper breakdown and identification of parts. Spliting the clamshell is a "pain in the neck" for these little units, but you"ll likely have to do that to find your internal leak. Carefully avoiding electrically exposed parts, spray a soapy water solution at suspected joints if the leak is not obvious.

Don't know three in one is, capacitor?
The compressor has oil in it. If the unit is layed on its side, compressor oil can leak out into the refrigeration tubing. This can cause a refrigeration circuit clog. Leaving the unit disconnected, upright, for a few days, sometimes fixes this oil clog.
If it sprung a refrigeration leak, it's another story, it needs a service tec looking for a leak. Then repairs, just chuck it or invest in this nice unit on repairs.
If compressor and fan blowers all run and work, the electric portion is good, compressor line gets hot, the other one cold.

Is the unit level? it's pulling moisture out of the air and not draining threw the drain hole normally it's cause by the unit not being leveled.

remove the back airfilter, and touch the tubes while the unit is running, if nice and cold, all is well, there just isnt any moisture there. but if compressor is running and tubes are warm , means freon/coolant has leaked out

You need to have a pressure gauge the reads for R-22. (Freon) It sounds like the system might have a leak. Look for a wet place any place on the units pipe system. It has a little oil in with the freon that is forced out of any leak. If you see a wet place this is oil. It is also the location of your leak.

It depends where the leak is. If its in the coils, you have to replace it. If the leak is easy to get to it would be cheaper just to fix it. So it all depends where the leak is. but 15 years is kind of old for a unit.

Ohhh that's sounding bad. Basically if the "gas", "freon", "refrigerant" whatever folks want to call it these days leaked out the system then the unit will run forever trying to satisfy the thermostat setting... but never getting there. It is most likely you have a "sealed system failure". Usually these are warrantied for 7 years so check your paperwork. You could look around the lower tubing area for an oily type substance... that is the oil in the system and if the gas leaks out the oil will too.

In a nutshell, the unit is dead without freon gas medium to circulate around.

if you never had that problem sounds like your oil is over ful and blowing thrugh your beather (crank case vent tubes) check and lower your oil level as needed and clean or replace air filter , should fix your problem

This may be a mojor problem. I have seen several refrigerators over the years which had a bad joint on the refrigerant tubing, and all the refrigerant leaked out. Try taking the back cover off and inspecting the area around the compressor. It should be nice and clean and dry. If you see any oil, that came from inside the normally sealed system. Sometimes if you turn the unit off for a while, then turn it on you might even hear some hissing of escaping gases at a leak for a minute or two. If this has not run long it can be fixed, but if it has run for a few days the unit may have sucked in a lot of moisture which can cause a premature death of a refrigerator. This is one of the few times I would advise to unplug the refrig and call for factory authorized service (rather than keeping it running until service arrives) Again, this is one of the few times (if you do indeed have a refrigerant leak) with a new unit like this I'd push the retailer or the manufactuer to replace the entire refrig instead of setteling for a repair.