A/C not blowing cold, but pressures are fine

[Ron]

As noted before, your pressures at cut-off are near perfect. Your OP said the cycling seemed fine, later it was "perfect". If you didn't change anything and it changed to long off - short on, you should find out why first. (Forget about air flow/duct work/etc for now.) If it has been long off - short on all along, I would suspect the orifice (restricted, not blocked) and since the high side is not going high and the cut-out pressure is correct, I would suspect the charge is low as well.
(If the cycling is OK when dead cold (has set overnight) then goes long off - short on, there is probably moisture in the system, freezing in the orifice...)

If the charge is low, the low side will not be replenished as fast as it needs to be. The pressure will drop causing the switch to turn the compressor off. It would cycle more than normal, short - short/medium. Add a blockage, short-long, high high side, negative low side (if you bypass the switch to force below 30 for a test). Add a restriction instead, short-long, high side pressure would depend on how low the charge was, same for low side. It may not go low/negative before the switch turns off, as your does not...

I agree it is time to look at the orifice...meanwhile recharging will eliminate a lot of guesswork...

You didn't say if the accumulator is getting cold now?

EDIT:
WSManual N:09:01
R-12 Pressure Check.jpg

[Bitsyncmaster]

As others have stated the blocked orifice would make the low pressure side pull down very quickly and take a long time to come back when the compressor switches off.

When I tried the VOV orifice my tubing had a bend in it and it just about shut the thing off. Result was compressor ran for a few seconds and took more than 60 seconds to come back on.

[Project Vixen]

Ok. That all makes sense. I found you could actually adjust the cutoff pressures on the switch from this video -- https://youtu.be/lt1oarL0soE. Should I be adjusting it down to 20? It'll be easy enough to put some more R12 in as i have the big tanks. Which is a better next move?

[Bitsyncmaster]

Ok. That all makes sense. I found you could actually adjust the cutoff pressures on the switch from this video -- https://youtu.be/lt1oarL0soE. Should I be adjusting it down to 20? It'll be easy enough to put some more R12 in as i have the big tanks. Which is a better next move?

The low pressure setting is to prevent freezing the evaporator. Since your not cooling the evaporator much, just jumper the connector and test the result.

When I top off a system, I set the fan on speed 4 and the selector to NORM AC. Stick a temperature in the center vent and read the temp after running a few minuets. Then add a little refrigerant and see what the temperature does. Also monitor the high pressure side. Usually when your get to much refrigerant in the temperature will stop dropping and even start to rise. The high pressure side will keep going up as your add more refrigerant.

[Ron]

Ok. That all makes sense. I found you could actually adjust the cutoff pressures on the switch from this video -- https://youtu.be/lt1oarL0soE. Should I be adjusting it down to 20? It'll be easy enough to put some more R12 in as i have the big tanks. Which is a better next move?

Why would you want to adjust it to 20 when it is at 30, exactly where the manual says it should be???

{Pass the popcorn, Rob. }

[Project Vixen]

Why would you want to adjust it to 20 when it is at 30, exactly where the manual says it should be??? }

Dunno. It's what all the cool kids with Youtube accounts are doing these days...

I'll try adding some R12 and see what happens.

[DMC-81]

~snip~

EDIT:
WSManual N:09:01
R-12 Pressure Check.jpg

Ron, thanks for posting that chart. I remember seeing that somewhere but couldn't find it when needed.

Yes, and is a high pressure of 185 completely normal, or perhaps another symptom of a blockage? I recorded 150 ish at 81 degrees ambient. The instructions I followed said that was normal for a full charge.

Also, it answers this question. Both Dave's and my pressures are in range at the slightly different ambient temperatures. Although would high pressure range at 85 ambient be 167.5 - 195 rather than 167.5 - 185?

I'll try adding some R12 and see what happens.

I think that's a sound plan.

[DMC5180]

Dunno. It's what all the cool kids with Youtube accounts are doing these days...

I'll try adding some R12 and see what happens.

All the Cool kids are converting to 134a, which does require a lower pressure adjustment down to 25-27 typically.


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[David T]

Before you go messing with the pressure switch you should make sure you have the correct amount of refrigerant in the system. You can't do that by just monitoring pressures, not accurately anyway. Rare to have to touch the switch unless, as Ron mentioned, you change the type of refrigerant.

[Ron]

Dunno. It's what all the cool kids with Youtube accounts are doing these days...

I'll try adding some R12 and see what happens.

Beer says it goes short-on, ~long-off (Low side-30, high side-something higher than 185) @ 85F. Or, you get a big grin on your face...