Automotive Air Conditioning Information Forum

Hi, looking for some advice and guidance on my 72 Ford factory AC system.

Background:
OEM ford system. At some point the system was upgrades as follows; I assume it remained on R12, not sure how to tell.
-Parallel flow condenser
-Sanden 9285
-Barrier hoses, o-ring

Was holding pressure when I bough it, I got the system working, added some R12, performance was poor. Disconnected heater, that helped a lot. Fan motor shot, all wiring burned out. Then rebuilt whole truck, now trying to improve and re-install system. I recovered the R12 that was in system, and I have 2, 12oz cans of real DuPont R12.

Current overhaul:
I have completely rebuild the in cab HVAC box. New seals, new fan motor, adjusted door linkage. OEM evap, flare fittings.
New drier
New hoses, o-rings
added fan shroud, changed to clutch style fan.

Questions;
Refrigerant type - Plan to keep system R12, unless there is good reason to change. Now is the time to decide. Since I have R12, it appears to be easiest/cheapest option. Concerned if it leaks out, obtaining more. Assume I should replace condenser and oil if going 134, flush evap.

Oil - I assume existing oil is mineral. Considering switch to a Ester/POE type. If I do, then future 134a conversion would be easier. Not sure there is a downside. System evac was done after engine was removed. So assume vapor recovery. Not sure how much oil is in recovery tank with refrigerant or left in system. Should I drain compressor and replace oil? How much? equal to what came out, or put in a specific amount?
I bought some of this on recommendation of local AC shop (manufacturer in this case)
https://www.aircomponents.com/product/f ... -8-oz-can/

Refrigerant quantity - The system is a mis-mash of things, and I don't have a good scale to determine amount in recovery tank. Beyond pressures and split temp, how to determine when system is adequately charged. All liquid in sight glass on drier?

Fittings- R12 screw on fitting suck to work with and make a mess when adapter/hose removed, can blow out o-ring. Considering updating to 134 quick connects. Thoughts?

If you're going to use R12. When the sight glass clears.

If you have a PF condenser? I would go with R134a. Works great when pressure correct!

Hi Tim,
Thanks for your help.
Yes have an existing PF condenser. Not sure it can be effectively flushed, or if it needs to be for 134 conversion.

Any advice on oil situation appreciated.

Justin

They cannot be flush with the average equipment seen on the market. A closed-loop flushing machine can flush PF condensers.

Any additional advice appreciated. 12 vs 134, oil, thanks.

Looks to be set up for R134a. Oil, DEC PAG 46.

I can only assume it is set up for R12, and was running on R12. Has R12 connectors and an R12 specific pump (9285). That said I assume it has mineral oil in comp/cond/evap now. Guessing these parts were installed in the late 80 or 90s, but have no idea.

Question is, should I
a) do nothing, put captured refrigerant back in, run as-is
or
b) use Ester/POE oil and run R12, so 134 conversion is easier at a later time.
or
c) Convert it to 134 now

If I convert now, should condenser be replace so it is not contaminated with mineral.

Perhaps I'm just not understanding your advice, I do appreciate your time. I think you are suggesting option c, convert now. flush, replace cond. use PAG oil. I'm in phx area also, Chandler. Getting hot, trying to decide and finish this up. Thanks again.

rattle_snake wrote: ↑Wed May 26, 2021 12:20 pm I can only assume it is set up for R12, and was running on R12. Has R12 connectors and an R12 specific pump (9285). That said I assume it has mineral oil in comp/cond/evap now. Guessing these parts were installed in the late 80 or 90s, but have no idea.

Question is, should I
a) do nothing, put captured refrigerant back in, run as-is
or
b) use Ester/POE oil and run R12, so 134 conversion is easier at a later time.
or
c) Convert it to 134 now

If I convert now, should condenser be replace so it is not contaminated with mineral.

Perhaps I'm just not understanding your advice, I do appreciate your time. I think you are suggesting option c, convert now. flush, replace cond. use PAG oil. I'm in phx area also, Chandler. Getting hot, trying to decide and finish this up. Thanks again.

Depends.

R134a

Drier needs to be replaced. Oil needs to be replaced. Old oil should be removed. Do not flush the condenser as you will never get the flushing agent back out. PF replacement condenser is not that much. And you already have a universal, so hoses will match. Conversion fittings and a label. In my book, when used with the right components. R134a works well. So that would be the route I would take.

After re-reading this thread and viewing the photos, I get "mixed signals" about what was done to this system. Some of the components seem to suggest it was converted to R-134a at an earlier time, yet it still has the R-12 1/4" flare fittings and a R/D with a sight glass, suggesting R-12.

What you could do is take the tank into which you recovered the refrigerant to a local professional A/C shop and have them analyze the contents. If analysis shows a mixture of refrigerants, then you'll know that you charged some R-12 into a system that was previously converted to R-134a, which would also explain the poor system performance you noticed.

If that's the case, I agree with previous comments that you should just convert it to R-134a now by draining the compressor of its oil, flushing it several times with PAG oil (not flushing solvent), flushing the evaporator and lines/hoses, replacing the condenser and R/D, evacuating well, adding the correct amount of PAG oil, and recharging to about 80 percent of the original R-12 specification.

The two cans of R-12 that you have on hand probably won't be enough anyway. Older R-12 systems like this one usually take three to four pounds of R-12 to fully charge them.

Hi John,
Thanks for your help.
Yes, unknow exactly what I have here. I'm guessing the old york comp and everything but the evap was replaced pre-r12 ban. The job was a hack.

As stated the system was holding pressure when I bought the truck, which I found odd. The pump was so mis-aligned it was not possible to install belt. I moved fan, pump, got it running and tested pressure. low so I added one can R12 and they came up to reasonable values, cooling performance improved. Split temp not great. No fan shroud so poor airflow over condenser. high side too high unless another fan blowing on cond.
But after short drive heat from heater core overwhelmed AC. coolant control valve shot, so disconnected heater hoses. noticeable improvement but performance still poor.
Fan motor bearing shot so fan overcurrent had already burned out wiring. The clutch coil inductance/voltage kickback had damaged all A/C control switches. I bypassed completely and ran fan on new circuit and limped it for a few months.

System needed complete overhaul. One of the major problems I found was heat bend door did not close all the way and allowed air flow across heater core instead of condenser in 'A/C' mode. I modified linkage system to resolve.

I could have captured refrigerant analyzed, but thinking just moving forward with 134a conversion mainly for availability of refrigerant for future maintenance.

Since the only part left from original system is evap and thermal expansion valve, not sure what capacity it needs. Guess I will start with 80% of 3 lbs = 38 oz 134a and go from there. comp states 175 cc, so 6 oz, PAG46. Have new hoses and new drier. Plan to get new cond. Only have to flush evap/TXV. Assume I should inject solvent in high side.