1973 coupe getting ready to sale.

[Mark873]

Been a long haul with this car, sat for over 10 years. too many other projects came first. Took it all the way down to bare metal, old paint was cracked, clear coat on metallic(&*#@!*). New OME Grabber Blue paint. Rebuilt FMX trans. 2V 351C runs strong. 136,000 miles. Don't know the history on the motor, high compression, doesn't smoke or burn oil. think it was rebuilt. Replaced most of the interior. Got all the lights working even the dash Seat Belt warning light. fun car to drive, gets lots of looks. don't see many of these on the road. Last of the big Mustang coupe.
AZ car, going to put it up for sale soon.

 

[Mark873]

Question for anyone that knows AC on 50 year old cars, have a new York AC compressor, changed to R134, charged system to @80% 30 low 200 high. the compressor sounds like it getting ready to toss a rod, belt slap, pulls down the engine. Gets cool not cold air.
Seem like it is working too hard, Question are these York's not made for R134? too thick/heavy?
Took car to an AC mechanic he said the new compressor was bad, got another one doing the same thing.
Found that reducing the amount of 134 it gets better.
System flushed, new condenser TEV and dryer, system evens out when engine stopped no blockage.

 

[Steve McMahan]

Do you know Igor your heater control valve is working? If the heater core is getting hot coolant, what you’re experiencing, from a temperature basis, is common. Regarding the 134a issue, you should be able to google the low/high pressure standards, bases on the outside temperature.

 

[Mark873]

Do you know Igor your heater control valve is working? If the heater core is getting hot coolant, what you’re experiencing, from a temperature basis, is common. Regarding the 134a issue, you should be able to google the low/high pressure standards, bases on the outside temperature.

Thanks for reply, have checked the AC/heater operations watching all the valves/gates seems to be operating correctly.
Did down load AC chart. Car in southwest and it been hot. No tint on windows and limited insolation.

 

[Nam Vet]

Not knowing how you flushed the system out, these cars can run AC just fine with R134. Check the door movement inside the climate control plenum for proper operation. Some doors are actuated by vacuum and some by control cable. Your pressures on the high and low side seem inconsistent with the ambient high temps.. Just because the compressor could be new, doesn't mean it's good. That knocking noise in the compressor indicates a blockage somewhere in the system.. Double check the amount of compressor oil. Too much can cause back pressure to the high side. On a system flush, ALL lines and AC components must be blown out thru incoming and outgoing to clear the blockage.

 

[72MustangSprint]

Just got my a/c fixed and they had to replace my expansion valve. Works good now after many years not working.

 

[Steve McMahan]

Great to hear. What I was speaking about is a valve that under your hood that you’ll see on your heater hoses going into the firewall. It’s a vacuum operated valve that turns off the hot water flow to the heater core when the AC is turned on. Just verify that the valve is working and closing when you set the controls to AC. If it’s not then the heater core heat generally overwhelms the AC cooling system and you get lukewarm cooling air.

 

[Mark873]

Not knowing how you flushed the system out, these cars can run AC just fine with R134. Check the door movement inside the climate control plenum for proper operation. Some doors are actuated by vacuum and some by control cable. Your pressures on the high and low side seem inconsistent with the ambient high temps.. Just because the compressor could be new, doesn't mean it's good. That knocking noise in the compressor indicates a blockage somewhere in the system.. Double check the amount of compressor oil. Too much can cause back pressure to the high side. On a system flush, ALL lines and AC components must be blown out thru incoming and outgoing to clear the blockage.

thanks for the reply, flushed only the A coil and the lines everything else is new, pushed a lot of air through the parts I flushed. used pressure canister AC flush kit. @ 1.5 inch oil in compressor.
the compressor will cycle in and out, the plenum under the dash and line at the compressor will get cold to the touch.
will look again at the door operations need to research which way the doors move. moving the controls seems like all the function are working correct, high low, heater, defroster, vent.
will check the high low pressure again.
thanks

 

[Steve McMahan]

This is the valve I’m referring to, under the hood:

 

[Hemikiller]

The valve Steve is referring to is critical to obtain cold output temps. If it's not closed, the output air will always be lukewarm. The temp selector cable pushes the blend door arm into the control switch for the water valve. If it's not adjusted correctly, the water valve will not close.

The shop manual has full explanations of which doors operate in which control positions, vacuum diagrams etc.

 

[mrgmhale]

In the event you determine mechanical repairs are needed for the York compressor (or replacement with a rebuilt unit), I suggest you contact the Original Air Group (a division of Classic Air Conditioning). Original Air specializes in helping folks with parts for older A/C systems. I have found their support techs understand what they are talking about. You may only need to pull a vacuum down in the system, and recharge it taking care to not overcharge the system. I can still get R-12 via ebay for my oem A/C system in our 69 Shelby GT500.

If you decide to replace the York compressor with a newer unit (Sanden), and to use R234 instead of R-12, please be aware the compressor oil for R134 is not compatible with the compressor oil from the R-12 system. You will need to remove the old compressor oil and use the new compressor oil that is designed for use with R134. The folks at Original Air can hook you up there also.

QAlthough we are running R-12 in the original A/C system on out 69 Shelby, on both 73 Mustangs we added Classic Air systems to those non-A/C cars. The add-on A/C kits both had Sanden compressors, and of course R134 refrigerant. Those two aftermarket systems work very nicely. Not one issue or complaint is coming from us. But, I am glad we are able to continue using our original A/C systemin the 69 Shelby.

 

[Mark873]

mrgmhale, thanks for the info, gives me ideas on what to look for.