134 high/low AC pressures in stock system?

[Tim Hancock]

I misplaced my notes from when I initially converted my stock '79 SC with York from 12 to 134. DIY 134 conversion in SC complete!

After 2 years of service, it needs a boost of refrigerant (not bad for all original hoses and fittings other than a new drier). I hooked up the gages and had 70 psi system pressure, I fired it up and with the deck lid down and 80 degree ambient, I put in one can and ended up with about 15-20psi low side and 200psi high side. My vent temp is mid 40's and all seems well. I just can't find where I originally came up with the proper pressures for 134 in a SC. I think I may have had higher pressures originally.

Anyone know the "recommended pressures" for a stock SC converted to 134?

[Tim Hancock]

bump for the PM crowd.

[Jim Sims]

You may be a bit low; but check with a thermometer at the dash air louver closest to the evaporator - add more refrigerant until the cool air temperature stops falling, then stop.

Engine deck lid down and engine running at 2000 rpm to pull air through deck lid condenser:

For 134a, approximate values:

Low side:
16 to 29 psi for 33 to 50 deg F evap temp
19 to 39 psi for 33 to 60 deg F evap temp
25 to 43 psi for 40 to 65 deg F evap temp
37 to 51 psi for 48 to 65 deg F evap temp

High Side:
115 to 200 psi for 70 to 80 deg F ambient temp*
140 to 235 psi for 80 to 90 deg F ambient temp*
165 to 270 psi for 90 to 100 deg F ambient temp*
210 to 310 psi for 100 to 110 deg F ambient temp*

*temperature of air moving over condenser usually measured two inches in "front" (front is side receiving air first) of condenser.

If the pressures you measure are too high and you have air moving over the condenser(s) while you are measuring pressures then you will likely benefit from less refrigerant.

[Tim Hancock]

Thanks Jim, I will leave it at 200 high pressure for now as it seemed to be working well and by your numbers posted above, I am in the ball park. (I was indeed running at 2k with the deck lid down resting on my hoses and a fan blowing air at my left rear wheel well and the ambient temp was 80 and the AC evep blower fan was on high.)

I now know that I can always shoot a bit more in if it seems lacking on the highway once we have another real hot 90+ day.

[steviee7]

Do you have the quick release service ports on yours? I tried adding them but my compressor fittings have larger threads on them. I can't seem to find them at the local parts stores. Do you know where I can buy them?

[Tim Hancock]

Originally posted by steviee7
Do you have the quick release service ports on yours? I tried adding them but my compressor fittings have larger threads on them. I can't seem to find them at the local parts stores. Do you know where I can buy them?

I have an old set of r12 gages that have the 45deg flared connections on them. I hook these to my service ports on the York, then I simply thread a 134 adapter that I have left over from some other conversion I did years ago, on the center fill port of the gage set, then attach a cheapy 134 hose and can to it.

Works fine, but should I ever sell the car, I will want to put some proper adapter fittings on so the new owner can take it to an AC shop (I will probably die while owning this car however ).

[steviee7]

just spent some time on our hosts site and didn't find anything to help me. My compressor looks as if the ports are permanently attached. That doesn't seem right!? It's getting hot here in Florida...

[Tim Hancock]

Originally posted by steviee7
just spent some time on our hosts site and didn't find anything to help me. My compressor looks as if the ports are permanently attached. That doesn't seem right!? It's getting hot here in Florida...

I am not sure, but I think your '86 has a different compressor than my "boat anchor" York, so I do not have an exact answer, but I am sure there is a solution out there.

[Tim Hancock]

If your car is stock check this link out. http://www.griffiths.com/shop/index.php?main_page=product_info&cPath=15_16_17_70&products_id=93