70 Dodge. Empty system-how do I know if it was filled with R134A or R12?

[watchfatha]

Hello All
The 70 Dodge I have has no gas in the ac system. The shrader valve on the high side is covered with a blue cap, usually signifying R134 has been used. However, the fitting on it and the low side is still the same as was the case with R12. I have both gasses. How can I tell if the system was actually filled with 134 (and has the proper oil) or was just on R 12 but the caps were just handy? Any way to determine this?
Thanks

 

[commando1]

Pics of the valves please.

 

[Davea Lux]

If a licensed shop did an R-134a conversion, they should have installed snap type R-134a service ports as part of the conversion. They also should have installed the appropriate sticker designation for the R-134a charge.
(Some also painted the compressor heads blue) Check the expansion valve to see if is says R-12 or R-134a on the head. Since the system is empty, you can also check to see if the EPR valve has been removed. On a normal conversion to R-134a, the EPR is discarded because it is not needed.

Dave

 

[CBODY67]

Since the system is empty, you can also check to see if the EPR valve has been removed. On a normal conversion to R-134a, the EPR is discarded because it is not needed. Dave

If the EPR is removed, what modulates the gas pressure or is making it a cycling-compressor system (i.e., A-body OEM) part of the conversion?

Just curious,
CBODY67

 

[Toolmanmike]

A freon identifier will do the job. Now you need to find a shop that has one. It sounds like you may not know for sure because of the caps. I fill mine through the low side so I would have a conversion on the low side line. I have seen it done both ways. Just a bit different procedure.

 

[Davea Lux]

If the EPR is removed, what modulates the gas pressure or is making it a cycling-compressor system (i.e., A-body OEM) part of the conversion?

Just curious,
CBODY67

The main function of the EPR valve with the R-12 system is to prevent evaporator icing by maintaining constant refrigerant flow and pressure in the evaporator. If liquid refrigerant comes in contact with the EPR valve, the valve closes on a drop in temperature and slows down the refrigerant flow. This controls refrigerant flow from the exit of the evaporator. This in turn allows the refrigerant in the evaporator to boil off which reduces icing. Also helps to keep refrigerant in liquid form from hammering the compressor and potentially causing damage. R-12 systems have flow control on both the inlet (expansion valve) and the exit tubing to the compressor. (EPR Valve)

R-134a is considerably less dense than R-12 which means it boils off more readily from liquid form so liquid transmission to the compressor is unlikely and the EPR valve is gotten rid of as part of the conversion to improve unit performance. Primary gas modulation on a R-134a system is done by the expansion valve and flow is controlled by the temperature sensitive capillary on the expansion valve on the inlet side of the evaporator.

Dave

 

[watchfatha]

All noted with sincere appreciation. No way of knowing who did (or did not do) this "conversion." I am making the assumption (I know, I know) that it was done by Curly, Larry and Mo's El CHEAPO AC repair. It is also possible that the original schrader valve covers were lost and these were just the handiest around-and were used without regard to signification of any particular gas, meaning there was NO conversion. I guess the best way is to find a shop with the appropriate sniffer (or similar device) and know for sure. I am embarrassed to say that I have a Snap On ACT 2500 Recycler but don't know how to use it. Anybody live in Socal/San Diego/Orange County and want to give me a lesson?

 

[CBODY67]

IF it was done "on the cheap", it probably had R-134a in it. Look for congealed refrig oil, too!

Best thing to do would be to do as complete an oil flush as you can do (condenser, evaporator, and compressor). Replace the receiver/drier, too, as a matter of course. Then re-fill it with R-134a and compatible oil. Then you can worry about the hoses not leaking and needing to be replaced. Aim for about 10% less gas charge with R-134a than R-12 (usually on the metal tag on the RV-2 compressor cyl head), but start at 80% and work up to about 90% slowly.

Another dynamic is regarding the freon re-cycling machines. Most shops used to have one for R-12 and one for R-134a. Reason for the two machines is that R-12 would contaminate the R-134a machine, which would mean the complete jug of recycled R-134a could not be re-used, but discarded. As we haven't had R-12 OEM for a long time, I suspect that few, if any, shops still maintain an R-12 recycling machine. Which makes the R-134a machine the default one.

The size of the fittings for the two gasses were designed to be different to prevent contamination of the recycling machines, too. A method to their "madness".

Just some thoughts,
CBODY67

 

[Davea Lux]

All noted with sincere appreciation. No way of knowing who did (or did not do) this "conversion." I am making the assumption (I know, I know) that it was done by Curly, Larry and Mo's El CHEAPO AC repair. It is also possible that the original schrader valve covers were lost and these were just the handiest around-and were used without regard to signification of any particular gas, meaning there was NO conversion. I guess the best way is to find a shop with the appropriate sniffer (or similar device) and know for sure. I am embarrassed to say that I have a Snap On ACT 2500 Recycler but don't know how to use it. Anybody live in Socal/San Diego/Orange County and want to give me a lesson?

If you PM an E-Mail, I can send you a PDF of the operator's manual for the 2500 series.

Dave

 

[CBODY67]

If you PM an E-Mail, I can send you a PDF of the operator's manual for the 2500 series. Dave

I suspect one primary item would be a fresh 30lb can of gas.

 

[Davea Lux]

I suspect one primary item would be a fresh 30lb can of gas.

R-12 machines of that era typically had a "Virgin" 30lb to extract refrigerant into (evacuated clean cylinder) and a 30lb R-12 cylinder to top off or replace the charge. The 2500 series was designed for R-12. Up until CFC's were designated as an ozone depleting hazard, little attention was paid to saving the R-12 as it used to only be worth about $20 for a 30lb cylinder.

Dave

 

[CBODY67]

Seems like the first re-cycling machine we got (when gas re-cycling first started, maybe from GM special tools?) was for R-12. Which had a fresh 30lb can in them. As I recall, the existing gas was vacuumed out, cleaned, re-oiled, and re-inserted into the system. The replaceable 30lb can was to finish the fill process with. Then R-134a happened and a new machine was purchased for that, keeping them separate and uncontaminated.

 

[Davea Lux]

Seems like the first re-cycling machine we got (when gas re-cycling first started, maybe from GM special tools?) was for R-12. Which had a fresh 30lb can in them. As I recall, the existing gas was vacuumed out, cleaned, re-oiled, and re-inserted into the system. The replaceable 30lb can was to finish the fill process with. Then R-134a happened and a new machine was purchased for that, keeping them separate and uncontaminated.

It usually worked best to have separate machines for R-12 and R-134a to avoid the contamination issues. Mixed gasses were not good for anything and were supposed to be disposed of by a certified facility. They charged a lot for that service.

Dave

 

[watchfatha]

Thanks once again for the instructive comments.

I am tempted to see if I can drain the compressor (is there a plug?where?) and observe whether there's any congealed oil. Wish one of you knowledgeable folks lived near: I'd be happy to pay for a lesson in how to use the ACT 2500 as I have 3 other oldies with AC, 2 of which are cold and still on R12. The third, a 1959 DeSoto with a period correct and functioning Frigiking unit in it, has strange ports that have no schrader valves in them, just twist on/twist off feature to an open threaded valve. Would like to switch them to more modern schrader valves as I have a strong belief that the only thing that system needs is some fresh R12 in order to start blowing cold. That's what took place with my 66 Imperial that had sat for 30 years and the Freon leaked out. I filled it with fresh freon and it has been cold ever since.

 

[cbarge]

From my experience working in a shop for 20 years....
Get the system evacuated. Ask the shop if they have a "garbage" tank they use to suck out the system for unknown situations like this.
Once evacuated they can pressure test the system and if all good switch tanks on the machine to fill your system with new freon and pag oil. Oh and new schrader valves too.
Hope this helps.

 

[patinated_imperial]

I have this exact situation with my Imperial as well.
Is it converted to R134a and hopefully had the oil changed to POE?
Does it still have the mineral oil from it's R12 days?
I tried to extract some oil and mix with water, as I read that mineral oil would not mix and POE would.
As already mentioned: The safest would be to flush the system, change the filter-dryer and the O-rings to H-NBR, fill compressor with POE (aka Esther), pressure test with nitrogen, pull a vacuum, fill with R134a.
I think the best way to drain the compressor is to take it off the car..

A guy from San Francisco I follow on youtube did a series on a 1962 Chrysler this summer. It is not edited, but he is very knowledgeable:






https://www.youtube.com/watch?v=q3C2cavQ-2Q
https://www.youtube.com/watch?v=V1q3F1m7K4g
https://www.youtube.com/watch?v=rQj_MRlomNE&list=PLjKapSILOyR8_VQUo-CYjFwp-G8Rk7krG&index=6&t=2s

 

[CBODY67]

Congealed oil can be found throughout the system's low places (i.e., condenser and such). There is supposed to be a drain plug on the oil pan of the compressor. The FSM should note where it is in the illustrations and section on the compressor itself.