Going to be vacuuming down my ac system soon ... And then recharge ... Any hints ?? Have the gear but not done before ,... ;)

Compressor cycling tells me you might be short on freon yet. You should be able to rev the engine to 1,500 RPM and hold for a period of time and the compressor should stay going. If the compressor is dropping out I would recheck the pressures again and might add some more freon. Because I hate to say it but I drive my truck not leave it sit and idle with A/C so the flow and pressure will change at road speed. Now also remember you sitting and idling there is no cold air flowing through the condenser so the high side pressure will rise because of this fact. I typically aim for 30-35 PSI on the low side at 1,500-1,800 RPM's this is the bottom of the low side switch and should stay on as long as the pressure doesn't fall more...

How about high side ? This was my pressure at idle ... Not 1500 ..... And I started getting nervous .....Still blowing 49 which is ok .... Never found a leak with backlight

Don't get too concerned about the high side pressure. There is a high pressure switch that will stop the compressor if it gets too high. At an idle you should be somewhere around 40 psi on the low side at about 75* or 80* ambient.

Cool thxDidn't think of the high perssure swich.I stopped at ~ 30 on low side ...... just cause the high side was concernng me ....... and that was at 850rpm (idle).

Ok. After adding turbo I lost cold air. Was wondering if I bumped a line or just coincidence. I hooked my gauges up and was showing around 20 psi on low side. So I added 1 can. Now when engine off I am at 70 psi on low side ... And 75 psi high side. If I turn engine on it cycles between 20-40 low side and compressor always on/ off quite frequently .I want to add another can so I can try and detect my leak - but is it safe given the 70 psi when engine shutoff ??? Thx

PicsShows 70 with engine offAnd high of 20-40 when cycling ac in idle

dabumpskie

Those pressures are normal when shut off. what is the high side pressure when it cycles rapidly?I usually don't even bother worrying about the low side when charging if its in the 20psi range is ok as long as it doesn't go into a vacuum or no pressure. The high side is the one to watch when charging. is the high side spiking when it cycles as usually when there is too much liquid in the system it will spike rapidly and the high pressure switch kicks it out. How many cans are in the system?

Those pressures are normal when shut off. what is the high side pressure when it cycles rapidly?

about 40PSI low side .... and 120 high side ?? I think I have a leak - but have blacklighted EVERYTHING .......... so I just want to fill it up again to do more blacklight detection tomight (run AC for longer). So thats ok ? I'll just keep the engine and AC running ..... and keep filling it until its 40 PSI on low side minimum ..... (its around 90 here today) If I can't find with blacklight - then guessing find someone with a "sniffer" ?? Can't think of anythign else

40 psi is too high for low side and 120 is too low for high side especially at 90*f. What is the humidity level?

40 psi is too high for low side and 120 is too low for high side especially at 90*f. What is the humidity level?

Low humidity (AZ). Like 30% Originally I vacummed and then filled to 30 (low) and (250) high and stopped. Had cold air for about 5 days - and couldn't see any leaks via blacklight. Then didn't use A/C for a few days and changed my turbo - cold air stopped. Figured I bumped a line or something. So chucked the gauges on (no engine start) ... and it was like 10 lowside and can't remember high - but under 100. So I added 1 can ...... and now it cycles between 20-40 with compressor always cycling ...... and high around 120. So I want to add one more can ....... in order to then run the AC hard to see if I can find my leak ????

Yeah you might have leaked down then, I would just dribble more in a little at a time and keep an eye on the gauges. 250 is pretty high. You should idealy be in the 170-200 range on high side in 90* weather depending on humidity. I wouldn't worry too much about the low side as long as its in the 15-30ish range. Best way to find a hard to find leak is to evac the system and just pump it up to around 150-250+ psi with air or nitrogen and listen and or use a spray bottle with water soap mixture and spary down everything and look for the bubbles when you hit the leak. its Faster and cheaper and a lot less effort than continuosly adding freon and blacklighting/sniffing ect and all the hassle.

If it leaked down - thats a fair amount in 7 odd days. Wonder why I can't find with blacklight ?? I have a new evaporator/heater core installed. And can't see any UV from that drainage port either ?? I'll add another can ....... what else would help detect the leak ?? http://www.harborfreight.com/electronic-freon-and-halogen-leak-detector-92514.html

That would constitute a fairly slow leak in the real world of finding it.If you can't find it with a balck light you definately will not find it with a sniffer. Like my last post stated if the black light fails just pressure it up and use soap and water and look for bubbles. This method never fails.

That would constitute a fairly slow leak in the real world of finding it. If you can't find it with a balck light you definately will not find it with a sniffer. Like my last post stated if the black light fails just pressure it up and use soap and water and look for bubbles. This method never fails.

Video showing.

Haven't added another can yet - wondering if I should vacuum it all back down .......... :banghead:

Definately low on freon by what the video showed. Looked like the low pres switch was kicking it out. must be a 15ish psi switch.

So even though it was hitting 40psi ??? So ok to add a can - worried if I add a can going to start hitting like 60+psi etc .......

John, you are letting the numbers scare you. The reason you will have high pressures with the truck standing still is because you don't have enough air flowing across the condenser. If you set a fan in front of the radiator then try charging it you will get better results. Here is what I would do: Put a fan in front of the radiator then hook up the low and high pressure lines. Turn the air on. I would not get too concerned about what the high side says. Get the low pressure up to about 40 psi (with it running)and see how the air feels. If you are happy then disconnect the gauges and shut the truck off. After a couple of minutes I would spray ALL connections and rubber hoses with a solution of dish soap and water. Give it another 5 minutes to allow the bubbles to form and look everything over real good. Tom

coolGoing to try and load a bit more - and run the AC as long as I can ....... and use SOAP as well as blacklight and see what I can find. Going to clean all connectors down and compressor to make sure any UV light is new.I question tho - you say to bring the LOW side up to 40 ......... but its already hitting 40 (15-40) ..... as its cycles ??? Yeah - definately a little overcautious - don't wanna see a BOOM

Not 40 as it cycles, but a CONSTANT 40psi when running. At an idle it should not be cycling much if at all. Far as things going boom, look down by the compressor and you will see a pressure switch. That pressure switch is there just in case the pressure goes over about 250psi and shuts the compressor down. The high side can very easily handle 300+psi.