Automotive Air Conditioning Information Forum (Archives)

Provided by

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

Unintentional discharge - how much oil to replace? & other questions

aribert on Mon October 07, 2013 1:34 PM User is offline

Year: 61
Make: Ford
Model: Falcon
Engine Size: 200
Refrigerant Type: R12
Country of Origin: United States

FIrst off I would like to mention that I first came to this forum site and the forum host web pages when I resurrected the A/C in my 91 F150 that had suffered black death (high press hose was plugged solid!). Four years later and the 134A retrofit A/C is still working good.

After putting it off for the past 3 decades, I have finally installed AC in my '61 Falcon. Under-dash evap unit from a 64/65 Mustang, , Sanden 508 comp, parallel flow condenser, all o-ring connections except at the evap. The compressor has the charge ports on the back plate. The suction service fitting has a 7/16-20 thread (same as the suction hose on my manifold set). The discharge fitting is smaller (3/8-24 thread). My high press service hose fitting is too large for this port. I found an adapter (I never checked that a schrader valve had been installed in the discharge port fitting!) mounted the adapter and proceeded with drawing the vacuum and charging. Pic of the adapter:

After charging, I went to remove the adapter - it looks rather cheesy and I figured the adapter was a future leak point. When I unscrewed the adapter I found out about the missing schrader valve. I have no idea as to how much oil blew out with the precious R12. There is an oil film on the firewall and an oil puddle on the floor still visible the next day.

I have Ester oil on hand (used it to lube the o-rings when making the hose connections).
1. How much oil should I add to the compressor to make up for lost oil?

2. Instead of an adapter, am I able to buy a discharge service port fitting that has the 7/16 threads? I can't seem to find such a part on the net.

3. I have some concern about the expansion valve:
at 1500 rpm: Low 12 psi, High 275, Vent temp 44F, evap core temp 36F; at idle: Low: 23, High 280 Vent: 50F
car was nosed into the garage. Ambient temp at the cond was 82F and at the passenger compartment 70F (Low side at 1500 seems too low and the High side at idle seems too high)

4. Roughly what does a 20 lb jug weigh empty? Just wondering how much R12 I have left. (I did not think to weigh it before I first used it - after charging 2 or 3 systems, jug currently weighs 25.4 lbs)

Thanks for reading this long post.

TRB on Tue October 08, 2013 10:50 AM User is offlineView users profile

1. It will always be a best guess in a situation like this. Maybe 2 ounces but I would try and judge by what you see on the firewall and such.

2. ?

3.It's an expansion valve system, so pressures will have a lower low side. How much refrigerant was added to the system?

4. Never weighted or seen a 20lbs cylinder.


When considering your next auto A/C purchase, please consider the site that supports you:

mk378 on Tue October 08, 2013 11:03 AM User is offline

Is it an isolation valve setup? With those there is no shrader valve in the service port because you're supposed to close the isolation valve before disconnecting the hose. If not, you should have a shrader valve in the 3/16 fitting (3/16 flare size, 3/8 threads) and use an adapter.

Charge close to the factory spec of R-12. The receiver should have a sight glass on it. With a PF condenser with a good fan and ester oil you have the option of running R-134a. The high high side you experienced even on R-12 suggests either poor condenser airflow or overcharging.

The standard disposable R-12 tanks were filled to 30 lbs net weight of R-12 and weigh about 8.25 lbs empty. Another way to estimate how much is left is to put the tank in a cold place to get the liquid inside cold. When you take it out and let it warm up, for a time there will be a noticeable difference in the temperature of the outside surface where the cold liquid ends and the gas space begins.

Edited: Tue October 08, 2013 at 11:13 AM by mk378

TRB on Tue October 08, 2013 11:13 AM User is offlineView users profile

I would like to see the fitting they are using, Have not seen all that many isolation valves on Sanden compressors.


When considering your next auto A/C purchase, please consider the site that supports you:

aribert on Tue October 08, 2013 11:34 AM User is offline

Thanks (very much!) for the replys:

Definitely not an isolation valve - just the "3/16" fitting (that has the 38-24 threads). I am guessing that someone forgot to install the schrader valve and STUPID me did not bother to remove the plastic dust caps on the service ports and look for the presence of the valve until I was ready to pull a vacuum - even though I must have handled the compressor a 100+ times while test fitting and fabricating the combo bracket for the comp and alt.

I put in 1.4 lbs in the system and there were no bubbles present in the sight glass at that time. I was expecting to add approx. 1.8 so I did not even look at the sight glass while filling. Next time I will slow down when I cross over 1 lb of fill. I am a bit limited in my scale - I am using a digital bath scale that reads in 0.2 lb increments. The '61 factory shop manual (for the Polar Aire system - I am using a 64 Mustang under-dash unit instead of the Polar Aire) says to charge until the bubbles disappear and then add 0.25 lb additional charge.

Thanks for the 30 lb tank weight and the suggestion to chill the tank an then let it warm up - I'm in the Detroit area and in a few months I can set the jug outside for a few hours and be able to read the condensation line when I bring it back inside.

TRB on Tue October 08, 2013 11:41 AM User is offlineView users profile

If you have converted to R134a and the good conversion fittings have the valve core in the adapter not the port. You can't have two valve cores, so the port core is removed.

I would say that system takes close to 24 ounces of refrigerant.


When considering your next auto A/C purchase, please consider the site that supports you:

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.