Hello
I'm the owner of a beautiful 1991 RX7 FC TII Vert.
When i bought the car i had no idea about A/C system status. Only thing i noticed was the system was completly out of refrigerant (pressure was 0).

Here i found a person that still makes R12 Freon recharge.
I charged the system with R12 and i added as oil a special product you can find here in italy that is called "SINTOFLON PROTECTOR KLIMA".
The Protector Klima is a special additive that is made with a mix of ester oil type Emkarate and micronized P.T.F.E. (Teflon). It is an exceptional product that protects A/C systems and it is also a light "stop refrigerant leaks".
I added this product because the a/c system of my FC has a slight micro leak. Indeed when i added this product i had no refrigerant leaks anymore.

There are no bubbles in the sightglass when the a/c system is running and i can see clearly refrigerant flushing.

Problem is that a/c system works intermittenly. I ALWAYS hear a/c compressor engaging when i push a/c buttos but the system someday cools and someday doesn't cool even with compressor working.

I have not changed the drier when i re charged the system. The drier was the original one from factory.

What can be the problem?

I read other threads about a/c problems in FC and someone wrote that ester oil can dissolve a/c drier bag and the small ***** in the drier can clog the system.
But i had this problem from the beginning when i charged the a/c system with genuine R12 plus the "Protector Klima".
It seems there is something in the pipes that sometimes clog the system and sometimes not.
Do you think that is drier related?

When the a/c system works correctly (someday it works) it cools so much that the air produced is really freezing as ice.

 

I just come back from a short travel with the 7.

For example today a/c doesn't make cool.
But an interesting thing i noticed: if i set the a/c blower to maximum and i just turn off the engine i can hear the refrigerant flushing sound from air vents for few seconds!
But it doesn't make cool at all. Air temperature is the same as outside.

Compressor is working, refrigerant is flushing......but it doesn't make cool!
Why?

 

IMHO you shouldn't have bothered with the R12 or it's equivalents. convert to R134a or R152 so any potential leaks or air pockets in the system can be quickly checked and corrected.

sounds like your charge is still weak, but it may be a blend door is stuck. it is not an abnormal occurrence in these cars for the door motors to jam or the control head to stop working properly. i find the latter unlikely if you are still randomly getting cold air though.

 

So what is the fix?

I made the (first) refrigerant charge on August 2016. Air conditioning last summer was working well apart the fact the first day after charge the system was stuck (no cool at all), then it started to work. Then occasionally is stopped making cool and the started to cool again.

I rested the car for the winter season (October 2016) with the a/c working and these days that the car is out again the a/c is not working anymore.

About the refrigerant level i see no bubbles in the sight glass when the a/c system is running.
I only see like "trembling water" in the sightglass when a/c is operating. No bubbles at all, only water that is shaking.

Do you still think that refrigerant level can be low?

 

see if your lines are both hot and cold, if they aren't much of either then your charge is weak or the compressor is having issues. if your high side line is cold and dripping in sweat and you aren't getting cold air then you should check the blend door to make sure it is open. it is also possible it is not cycling properly and the evap core is freezing solid. do you get cold air at first and then it just stops? that would indicate a freezing core.

 

No. When it works i get cold air from the beginning and it still continues to work. When it doesn't work i get warm air from the beginning (when i first start the motor).

Another thing i noticed is that when the a/c is working and the car is stuck in the traffic, even if the ac is setted to maximum, cooling is very low. But with the car moving at 50mph cooling is so hight that freezing ice air is coming out from air vents.

 

I checked that: my high side line is warm but not too hot!
My low pressure line is a little little fresh, not cold, close to ambient temperature.

Can it be something that clogged the expansion valve?

If my expansion valve il clogged can i do something for unlock it without disassemble the system?

 

Check pressures to discard a problem with the compressor.
Check pressure to be sure the system is charged correctly.
Check a/c or engine fan to be blowing properly.
Check your a/c pressure sender. You can jump the cable to activated the compressor and test if at low speed, the a/c is blowing cold.
Verify for any traces of oil around fittings lines, compressor clutch seals.
Dirty expansion valve is a problem. You need to remove it from he evaporator and replace with a new one.

You can replace the drier and expansion valve with universal ones. More cheap than genuine and works great.

 

Thank you very much for your support Nitrometano!

Problem is that compressor engages.
AC System worked perfectly last summer. I did a full recharge of genuine R12 Freon.

Is it possibile that compressor engages even with low refrigerant?

Another thing is that when system was working correctly (makes cold air) compressor engaged and disengaged after 20/30 seconds if the fan speed was not setted to maxium (at maximum fan speed compressor always stays on).
Now that the system is not working well compressor is always engaged in every fan speed cursor position.

Can it be just a low refrigerant problem?

In the sight glass i see refrigerant flushing. Like flushing water.
I don't understand if that flushing appearance is because there are too many bubbles.

 

Sounds like low refrigerant. The system has a low pressure switch but no high pressure switch. If the compressor clicks off and a few seconds later kicks on, it mean the suction line pressure is getting too low and it switches off until the low and high side equalize and it will kick on again.

You should see no bubbles in the sight glass, that is indicative of low pressure.

 

If you're looking for an organized series of tests to try, the FSM has a full procedure for checking everything related to A/C. Chances are if you have a gremlin in one place, he probably has a friend somewhere else in the system. Best to get the whole thing worked over, because you'll wish you had in a couple weeks