A/C question

[crobson]

Hello

Does anyone have or know were to obtain specs. on the a/c systems in our cars? such as what high side and low side pressures should be at a given outside temp. How much of a refirigerant charge should go into the system ect... I have a haynes manual and it dosnt seem to be in there, and I have looked around this site and the internet for a bit with no luck.

Basically my a/c dosnt seem to be running as effeciently as it should be so I preformed a checkout on it, I just need some numbers from ford to compare these numbers to.

os temp. 84 degrees f
humidity 40%
suc. line pressure 45 psig coresp. temp. 50 degrees f
acct. line temp. 57 degrees f

liquid line pressure 275 psig corresp. temp. 153 degrees f
acct. line temp. 165 degrees f

superheat of system 7 degrees f

subcool of system 12 degrees f

air at vents while parked 48.9 degrees f

thanks for any help

Chris

 

[matt0248]

There is usually a sticker under the hood that will tell you what the system holds for freon. However, it will not list pressures. The low side pressure when the system is off and allowed to rest to ambient temperature, the pressure will be roughly equal to ambient temp. Meaning if it is 85 F outside the pressure should be around 85 PSI. If it is not, the system may be low. As far as running pressures. Does the the compressor cycle at 45 PSi on the low side? This seems a bit too high, I thought they cycled lower than that. If your compressor is not cycling at all then it is probably low on freon. Running high side pressure really coresponds to how hard the system is working, so the hotter it is outside the higher the high side pressure will be, as long as is it below the high pressure cut off point it should be ok. Your vent temperature will lower as you start driving as air moves across the condenser.

 

[Exproblems]

>>>>>>>>>>>>>

Hello

Does anyone have or know were to obtain specs. on the a/c systems in our cars? such as what high side and low side pressures should be at a given outside temp. How much of a refirigerant charge should go into the system ect... I have a haynes manual and it dosnt seem to be in there, and I have looked around this site and the internet for a bit with no luck.>>>>>>>>>>>>

The Haynes manual I have says to check the "HVAC Specification Tag" for refrigerant capacity. I would imagine this tag is located in the engine compartment possibly on the radiator support, refrigerant resevoir tank or the compressor itself. If I'm not mistaken, new refrigerant bottles that you can buy in parts stores have a comparison chart on the back of them showing what the low side pressure should read according to outside air temp. You add referigerant till the pressure gauge reads in the good zone for what the outside air temp is. It is the low end reading of the pressure gauge "cycle" that you set the low side pressure to for proper fill of refrigerant in the system. I hope I explained this part right for you to know what I'm referrring to. Check how cold the air is coming out of the vents as you go. I remember seeing this chart on a bottle of refrigerant I bought last year for another vehicle of mine. FYI, if you go to top off your AC system, purge the air out of the hose line prior to adding the regfrigerant. You don't want air to get into the system.

 

[ExplorerLTD823]

Pressures...

According to the Ford service manual at 84 degrees, High side should be 190-290 psi and Low side should be 32-62 psi.
Generally I like to see the low side down in the 30s. Your low side is slightly high to me but not too bad - it's right within the curve in the manual. Your high side looks perfect. When you have good numbers and it's still not blowing cold enough, there may be air or moisture in the system. You may have a slightly high charge but I wouldn't mess with it. When I'm not sure, usually the best thing to do is get it on a machine and do a full evacuation and re-charge so that I know for sure how much is in there. The evac will get rid of any moisture and will also let you know if there are any leaks.

Hope this helps.

PB