Why is my A/C only blowing 60-65 degree air?

[Danford1]

Please help me understand this problem. 

I have a 67 Falcon Futura that came with factory air. About 10 years ago I replaced all under hood items I purchased from Classic Auto Air. It worked great blowing 38°-40° air. 

I sold the car in 2015. I just bought it back this year. The A/C only blew 60°-65° air. I figured it needed a recharge. It was evacuated, vacuumed for an hour and checked for leaks. No leaks ?

After a recharge with 24 ounces R134A measured on a postal scale, It produced the same 60°-65° air. 

I read where a bad expansion valve could cause this or the heater core supplying hot air to system. I unhooked and by-passed the heater core, no change. 

I then spent way too much money on a new expansion valve, re-evacuated system, vacuumed, added 1-2 ounces oil, recharged with 24 ounces R134A … and got the same results 60°-65° air ?

I uploaded a video on YouTube showing the gages. Low and high side show proper pressures 26&185 at 1500 rpm and about 37&190 at idle. 

I tried spraying water on the condenser and it only lowered temp 2-3° from sitting there idling under a closed hood. About the same as when driving down the road. 

No leaks in system, 80-90 degrees outside temp with a good portion of humidity (Michigan summer) and only 60°-65° air from ducts with No Heater Core connection.

When changing system the metal hose end coming from evaporator is frosted and cold. When system is operating the hose end is cold and dripping wet but not frosted. Everything seems normal. 

What is wrong?

Thanks in advance. 

Danford1 

 

 Here is a link to the video showing the gauges https://www.youtube.com/watch?v=0bnlcMTdLp4

[akirby]

Are you sure the blend door is working?  

[Danford1]

I’m 80% sure it is but without the heater core being connected, would it matter?

 It is a total pita to get to but I do have a bore scope I can use to look up there. It is on top of the heater box are very hard to get at. 

Edited July 27, 2023 by Danford1

[Flying68]

You may have a leak in the ducts, drawing in warm air that isn't passing through the evaporator, or your vent door is stuck open drawing in warm outside air.  Not sure if your system has a recirculation or not.

[akirby]

47 minutes ago, Danford1 said:

I’m 80° sure it is but without the heater core being connected, would it matter?

 It is a total pita to get to but I do have a bore scope I can use to look up there. It is on top of the heater box are very hard to get at. 

As flying68 mentioned it could still be pulling in ambient air.  Some kind of leak allowing warmer air to mix in seems most likely given that you replaced everything else and you are getting some cooling.  You could confirm by testing the temp of the evaporator coils if you can get to them.

[Danford1]

I took things apart today and checked the blend door and the vacuum operated doors. Everything works at it should. No vacuum leaks. Yes in max air mode it recirculates the inside air. 
I can’t get to the evaporator to take its temperature. 
I have a thermal imaging camera and it verified all temperature readings. The metal portion of the evaporator exit hose coming from the firewall under the hood is 60°- 65° same as air temp coming from vents. 
 Today I added about 7 more ounces of R134A as someone said my pressures were low. Pressures are now about 50&250. Seems high to me. Anyway it didn’t do anything for the air temp. Still a good 20° to warm. 
  I just drove down the freeway for 1/2 hour, same 65° going 70 mph ?

Edited July 28, 2023 by Danford1

[akirby]

Well that leaves the compressor and evaporator.

[Flying68]

The condenser could also be obstructed.  Basically the next step is to check that you have adequate airflow over both the evaporator and condenser.  Both should be free of debris in the fins.  The compressor seems to be functioning based on the difference in the pressure readings.  Although if the compressor is going bad, the extra friction could cause the discharge temperature to be higher than it should be.  I assume that when it was evacuated it was checked for debris in the lines, if not, that could be another culprit.

[akirby]

I’m leaning towards a partially blocked condenser (internally or externally).  But I see it also has a thermostat.  Did you check/replace the thermostat?

[Danford1]

Thermostat? I recently installed a 160° engine thermostat along with a new radiator. The engine doesn’t overheat. 
if you mean a thermostat in the A\C system the only thing I see is an electrical box with a temp sensing probe stuck into the evaporator. That is suppose to turn off the compressor if it gets too cold. My compressor runs constantly. I hooked a led to it so I can see if it turns off. It doesn’t. 
  If there is another thermostat in the system I don’t know where it would be. I don’t see it in the shop manual either. 
  No one mentioned the receiver dryer. Could that be an issue?

could the compressor be to small? It is different from the one I originally installed it is model B509-CL1220.

[akirby]

Yes that thermostat but if the compressor is on that rules it out.

[Danford1]

Yes, the compressor is always running. 
The thermal camera showed the condenser was working. 
  In the past I’ve had a Sanden compressor apart before. Easy to do and not a lot in them. 
 I plan to take the system apart, spray cleaners throw the evaporator in both direction and blow it out. I replace the dryer, clean blow out condenser annd and lines and take the compressor apart. 
 I don’t know why the original compressor was replaced or when. I suppose it could have sent debris through the system. I’ll clean out the system and start over ?