what is the correct pressure for R134a freon. My car is converted to R134a and i think it runs at a higher pressure than the oem manual states. It states on the low side (the side i can measure) is to be 21 to 28 psi which i think is for R12. Shouldn't the R134a pressure be higher?
Proper pressure for R134a freon
- Thread starter Halsupramk3
- Start date
At 90 degrees ambient, for R134a systems, look for about 200- 220 Pressures on the high side and about 25-30 Pressures on the low side at idle, and at 1,500 RPM look for about 220- 230 Pressures on the high side and about 20-27 Pressures on the low side.
When you refill, if you are unsure of the level, watch for when the bubles in the sight glass stop, and it goes clear. Stop because it is full.
http://www.cygnusx1.net/supra/library/TSRM/ac/AC_17.html
Supposed to use ~80% less pressure for a R134 conversion.
Supposed to use ~80% less pressure for a R134 conversion.
Bishop: I thought it was supposed to be less of a charge of the refrigerant itself, but would end up with higher pressures?
Right, well it's the same thing, just depends on how you charge your system. Some people charge by pressure, some charge by ounces.
And still others charge by the output temp. Charge till the vent temp no longer drops, while keeping an eye on high side pressure.
A/C and conversions is something we do everyday.
WE don't fill the system by the pressures, or the vent temps.
(we do use pressure for diagnosis, and to confirm a good operation)
WE fill the system by adding the correct amount per the manuf. specs.
(I have a book with every vehicle listed).
If there is a site glass, you can use that.
True it is 'recommended' to add approx. 80% when converting to R134a.
On my '89, My high side pressures (at 105* daytime here in the desert) are about 280*. I had to remove the high pressure cutoff sensor connector and place a jumper in it because the sensor shuts off the compressor at about 265*ish.
The High side runs higher pressures with R134a due to the condensor not quite being adequate.
A factory R134a system condensors disipate heat better.
Low side runs about 35psi. I keep a pocket thermometer in the center vent. Temp gets down to 40* before cycling compressor off, and back on at 50*. This is normal.
I also found that it runs this nice 'normal R12 type' cold temps when the system is 100% full of R134a.
If you don't have those 2 little A/C fans (or equal CFMs), you won't get enough air flow (around town) over the condensor to remove the heat.
The other problem with conversions not being as cold is...the R12 evaporators are a bit smaller than the factory installed R134a ones. One more row of fins will make a difference.
But hey, mine works great. I have those 2 little fans. They sure do flow some air !!
I did remove the fan and clutch, and installed an electric fan. I recommend one that flows at least 1600 CFMs. MR. Gaskets makes a good one with ball bearings, 1800 cfm, for about $65. Check this store for electric fans.
http://www.jegs.com/webapp/wcs/stores/servlet/TopCategoriesDisplay?storeId=10001&catalogId=10002
WE don't fill the system by the pressures, or the vent temps.
(we do use pressure for diagnosis, and to confirm a good operation)
WE fill the system by adding the correct amount per the manuf. specs.
(I have a book with every vehicle listed).
If there is a site glass, you can use that.
True it is 'recommended' to add approx. 80% when converting to R134a.
On my '89, My high side pressures (at 105* daytime here in the desert) are about 280*. I had to remove the high pressure cutoff sensor connector and place a jumper in it because the sensor shuts off the compressor at about 265*ish.
The High side runs higher pressures with R134a due to the condensor not quite being adequate.
A factory R134a system condensors disipate heat better.
Low side runs about 35psi. I keep a pocket thermometer in the center vent. Temp gets down to 40* before cycling compressor off, and back on at 50*. This is normal.
I also found that it runs this nice 'normal R12 type' cold temps when the system is 100% full of R134a.
If you don't have those 2 little A/C fans (or equal CFMs), you won't get enough air flow (around town) over the condensor to remove the heat.
The other problem with conversions not being as cold is...the R12 evaporators are a bit smaller than the factory installed R134a ones. One more row of fins will make a difference.
But hey, mine works great. I have those 2 little fans. They sure do flow some air !!
I did remove the fan and clutch, and installed an electric fan. I recommend one that flows at least 1600 CFMs. MR. Gaskets makes a good one with ball bearings, 1800 cfm, for about $65. Check this store for electric fans.
http://www.jegs.com/webapp/wcs/stores/servlet/TopCategoriesDisplay?storeId=10001&catalogId=10002
thanks for the info. My crappy gauge on the freon bottle says about 27 or 28 psi low side and is blowing cold. I went to gulf shores, AL with teh low freon and sweated my way back. Topped off the freon and now a/c is cold.
Yep, just a few ounces low will cause you to not be happy.:icon_evil
That is the nice thing about converting. You can add (top up)some R134a yourself at home.:biglaugh:
That is the nice thing about converting. You can add (top up)some R134a yourself at home.:biglaugh: