Got the AC recharged (again) and good news – it worked! All of the heater controls are working – the actuators open and close the air doors and properly route the airflow for AC, heater, and defrost. The fan works on all three speeds. You can see the heater controls both during the day and at night. The environment of the Imperial is finally controlled!
Well, sort of… The AC was more cool than cold. Actually, it wasn’t cold enough to really make a difference. After discussing the symptoms with the mechanic, it looked like high and low pressures were OK, but the differential pressure between high and low was too low. This is often a symptom of a problem with the expansion valve.
OK, let’s try a different expansion valve! This time let’s track down a better expansion valve than the inexpensive one from Rock Auto.
After a couple of weeks of tracking I couldn’t find a better expansion valve. With no other real choice, order another one of these expansion valves and see if it was a problem with the current valve – perhaps a defect or some dirt.
New valve arrived, old refrigerant sucked out, new valve installed, and new refrigerant stuffed in.
Significant improvement! The AC is now cold. Not ice cold, but cold enough that it will probably be OK. I need to stick a thermometer in the vent to see what the actual temperature is.
If this isn’t enough, the next step will be to replace the condenser. Modern cross-flow condensers work much better with modern R-134a refrigerant than the old style restrictive condensers and are a recommended upgrade when updating an old AC system. Even better, they are surprisingly affordable – I should be able to get one for around $200.
The downside is that they require new mounting brackets and new hoses. The mounting brackets are easy, but there is limited space to run new hoses. Maybe there is some way to use the existing hard lines with a new condenser? Need to study this a bit more.
On a side note, the mechanic told me that the thermal fan clutch on the engine cooling fan isn’t working. Of course I had replaced the fan clutch with a new one to ensure that it worked back when I put the engine together… Now to see if I can find the old one and see if it works. This could be another part of my ongoing cooling problems. Oh well, more tasks for this winter.