cut out pressure
- Thread starter bearman
- Start date
could you please explain your question for me,year of car,tranny,what you are aiming for. Guess Im getting old.
your not old, old is when you get my age. its just a general type question. i live in phoenix have worked on a few a/c units and finding that the low pressure side is cutting out around 10 to 15 lb mark on the gauges. but if i jump the cut out switch or install a adjustable one and set cut out at 5 lbs it really starts cooling well. once i have reached that set point i have the fan also set on high to help cool the condenser down. i do know that the factory or aftermarket have there settings that they like but was just wondering if anybody does there own thing with the switches and superheat etc. or do most people just drop it in and go.
ok now I understand, you should of mentioned ac
I would guess it shouldn't be much below 30-35psi. The evaporator will start to freeze up below that pressure.
Doug
Doug
Lefty71
Well-Known Member
Interesting question for sure, and I don't have a proper answer..... A couple things to keep in mind though, the law of averages is working against you here. I don't think theres ever been different AC units for different regions, and used cars would make it a mixed bag anyway. So cars are one size fits all from Maine to Arizona, and you are finding yourself with too small of an air conditioner to satisfy in your home region. Personally I would leave the cut-out a little higher as others have mentioned, because i'd be afraid to damage the top end of the compressor without adequate oil supply coming back in the vapor line at super low pressures. But I would investigate the possibility of an adjustable metering device, or replace with a larger one and then go with a smidgen more refrigerant (just don't slug it). I have heard of people running slightly more refrigerant than the factory calls for and getting really good results and super capacity at highway speed, but its a dangerous game without the knowledge needed to know when to stop. And I don't have the level of experience with cars to say for sure what you can get away with. Maybe some old parts books or a service manual for your year and model will tell you if the dealer offered any options for adjusting the output to match your region?? I'll have a look at the Chrysler/Imperial one I have and see if it offers any insight. HTH, Lefty71
5.7 the after market offer a few switches that you remove your old one and install the new one. hook up your gauges if your old cut out was (example) 20PSI the new one has a adjustable screw between the electrical prongs. i have ran the idle up to what would be highway speeds and adjusted the switch so the clutch kicks out later. while the the cut out is now down to 10psi the temp inside drops to 32 degrees which is freeze point. well i then adjust back up at highway speeds to 12psi and temp inside levels out around 36 degrees. evap doesn't freeze up and vent temps are great. at this point you can run in normal traffic and not have the clutch cycle all the time as a result less wear and tear on compressor and clutch not to mention cooler air.
Lefty71
Well-Known Member
Minor follow up. The service manual that I read from '72 didn't add a lot of valuable info in this regard, other than the fact that Chrysler did use a ETS sensor on the higher end cars (Auto-Temp), maybe only on Imperials, but anyway it did sense the evaporator temp and allow the compressor to run longer cycles, and therefore drag a little more capacity out of the system, as long as it wasn't freezing the evaporator up. If it was freezing, the sensor would shut it down for a few and cycle that way instead of the EPS? sensor which shut down the compressor on low suction pressure, like you described. No mention of the region or maximum capacity these were designed for, but I got a feel that they think they should work at passenger car size anywhere it is below 120F as long as the humidity was not too high. And wagons I guess may need two systems likely due to additional occupants, not space size. So, I don't know where you would find the right part for your install, but maybe adding an evaporator freeze sensor could help you out in this situation?? HTH, Lefty71
lefty71, thanks for your input will dig deeper. as for right now what i have done has had great results but to add a evap sensor for freeze point would be a nice option. also thinking of adding a sub cooler to the condenser.
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