sorry this title is wrong. It cools enough for me, but maybe i should PM it.

The system has not been checked for 20 years? I suspect a refrigerant leak. Find a competent HVAC company and have them check the refrigerant level. If it is low, then have them find the leak. Adding R22 refrigerant and having it leak out is an expensive way to keep this old timer running.

Out of hundreds of complaints I've had about insuficent cooling,I estimate less than 10% was due to low charge. I commend you for trying to extend the units life but based on your statments, I'm not certain you will get reliable information. 1 in 500 techs "might" be capiable of testing cap mfds but those that can don't need help troubleshooting the rest of system. Which bring's me to ask why do you own the test device and where did you attain training to use it? Since you own this unusual device is it safe to assume you also own and know how to use all the tools techs use daily? How did you verify return air system is leak free? I'm not picking on you,just want to be assured you aren't blowing smoke up our kazoos before I spend time walking you through tests to find the problem.

1-when i want to know something i learn about it. Usually reading and watching vids is enough. However, if i need to ill ask questions too.

2-i taught myself how to use vom and oscilloscope in grade school. Parents thought a career in electronics was in the making, so signed me up at the tech school, but after a year i got bored with electronics.

3-still that vom, which years ago became a dmv is a very handy tool for working electronic issues on car and house. My soldering iron comes in handy too from time to time.

4-ive inspected more then 90% of all ductwork with my hands feeling for leaking air as the unit is on. That includes all joints and fittings. The remaining 10% i can see and looks fine. The actual return is just a hole in wall with a filter.

5-when i bought this house in 1986 i found many ductwork leaks that i fixed with duct tape. Ive learned since then not to use duct tape for ductwork, but this original repair from 1986 is still holding.

6-i can feel strong air coming from each vent.

7-im 60 yo and ive learned so many times that if u want it done right, then do it yourself.

Ok I see what you are doing so I'll tell you how to check two items that have already been checked off and you can pick the rest up as you have in the past. Measure air temperature as it enter's return grill and again near as possible to where air enter's blower. Sometimes drilling hole for thermometer probe in handler and sealing with a screw or castable sealer is easiest way to test near blower. If there's any increase in temp,there's a leak and/or poor insulation. If coil has never been cleaned and there's much lint and dirt inside return downstream of filter you can bet coil is dirty. Dirty coil is not causing less than normal temp drop accross coil but keep it in mind until this problem is solved. A leaky return will effect temp drop so check that carfully. Since outdoor coil is clean I wouldn't look much farthar until refrigerant has been tested. If that is ok the next suspect might be insuffecient supply duct insulation. Good luck. I still don't know how that cap was tested but it no longer matters.

Thank you for your response.

The blower is about 10" inside the return grill. Literally 10". It would be harder here to feel for leaks, but ive done the best i can and years ago I covered all the edges & seams with duct tape. Also taped shut the side door on the air handler. Ive thought about replacing that with the foil backed true duct tape, but haven't.

Yes im concerned about dirty evap coil, but there is literally no way to inspect that without complete tear down of this unit. I can show u pics.

My dvm has a capacitor tester. Remove cap, discharge it, then hook up the meter and wait for stable reading. Remove meter, wait a few minutes and test it again. Maybe test it a 3rd time. If all reading were exactly the same, trust those readings. Just to be extra sure pull a few caps from parts supply and ck that they read as listed. Also tested the replacement cap i bought.

Did i cover all your points?

There is no grill. It broke years ago.

1952 house. Ac added later. They could have placed air handler beside house for a closer to central location. Maybe in hall closet, but since its a furnace heater, im not sure. However it was placed in garage on one end of house and a hole was punched thru the block wall for the return vent. Im gunna triple ck the seal for leaks. Cant do this from garage, need remove filter and look from inside house. I been wanting to buy foil tape. Just in case. Or is duct tape better here, since this has no actual duct work? What is good brand foil tape?

All tape secure in return. Looked over the entire cavity and it looks air tight.