# AC High pressure 450psi



## VETRAN (May 21, 2009)

1st time to post, Thanks in advance for any help,1987 HB ,Z24 105 k miles. Low 100, High 100 before starting. As soon as its started low goes down as low as 20 psi and climbs to about 45 psi and high keeps climbing to 450 psi then I guess it locks up and squeals. Outside temp about 90 deg. I bought 2 months ago with no AC working. I have a 87 Pathfinder for parts with working AC. I replaced the compressor which the old owner said was bad and also bought a new dryer. Then found the high side hose was leaking and swapped it. Found a o-ring leak and for the time vacuumed down and filled again. Still squeals and yes new, tight belt, bearings good and free spinning with belt off and pump free spinning. One mechanic said it was the expansion valve so I swapped the whole valve and cabin radiator / whatever its called. One mechanic says the New Dryer may be bad? The high side hose and pump seem to get awful hot. My guesses are getting expensive and time consuming. Poor and broke needs help...Curtis


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## VETRAN (May 21, 2009)

*Did I put this in the right section?*

Did I put this in the right section?


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## TheRepairMan (Jun 30, 2009)

Yeah, it's in the right section.

Sounds to me like you might not be getting near enough air flow through the condenser and radiator ...as in, possibly a bad fan clutch. That would also explain starting pressures at 100 each side to start. Those sound a little high to me also, but check the fan clutch ...uh, if it has one.

-Roger


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## smj999smj (Jan 1, 2006)

Sounds to me like you have too much freon in the system. Static pressures should be about 70psi on each side. You are putting the system under a vaccum before charging it, correct? How much freon are you putting into the system? Has the system been converted to R-134a?...if so, have you reduced the system capacity, accordingly (R-134a charge should be approx. 80% of the charge listed for the vehicle's original R-12 capacity)?


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## VETRAN (May 21, 2009)

Thanks for the ideas. I will check each Idea Tue. evening in detail...
The Radiator(s) seemed clean. I look closer. The clutch feels right, resistance but turns when cool. I may have too much freon, I put the same amount as R12 or about 40oz/ 2.4 lb. so I will release some. Yes I did vaccuume for over 30 min and it had about -30 psi. Back online Tue. Nite.


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## smj999smj (Jan 1, 2006)

That should be 30 inches of vacuum... It sounds like you definately have too much freon. I would have started with 26 oz. and see how it worked. Monitoring the pressure gauges and temperature output at the vents, one can add freon if necessary until the performance is satisfactory.


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## VETRAN (May 21, 2009)

I started with 2 cans / 24 oz. and it did not seem cool enough. It still squealed or locked up so added most of another can and cooling good but, locked up again. I then released some freon but, maybe not enough. I will drop to 70 psi and try again. Thanks


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## VETRAN (May 21, 2009)

Update: outside temp about 88 and before pressure about low=110 high=130. Without starting I released freon or pressure on low side of gauges that released out oh the freon line down to 75 psi. Start engine and low pressure went down to -5 before starting to rise to 22 psi. High side to 150 psi. My thermometer said insde temp was 86 but I think at this temp it is not accurate, feels like 76. Letting it run ten min. low climbs 18 to 24 psi and high cycles from 170 - 195. Turn off & rises to 80 psi. Dryer & cabin line cool to touch. High side next to Valve & radiator reads 160 degrees, seems hot. Maybe I let out too much freon but wait for replys first. PS radiators cleen. also put next to wall thermometer in house it reads 86 ,house 76.


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## VETRAN (May 21, 2009)

Murfreesboro Tn


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## smj999smj (Jan 1, 2006)

You need to put the thermometer in the center outlet vent. When the compressor locks up, it's usually an indication of too much freon rather than not enough. Sounds like you may have let a little too much out. Observe readings at approx. 2000-2500 RPM and you should see around 32 psi on the low and 175-300 psi on the high, depending on ambient temperature and humidity. Figuring the capacity on an R12 to R134a conversion can be a little tricky. Conversion kits recommend capacities anywhere from 70% to 90% and it's not an exact science as every vehicle is differant. That's why you need high and low gauges and a thermometer to figure out just how much R134a freon is enough. For that reason, it's best to start on the low side and see how the system performs and gradually add as needed until the performance is satisfactory.


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## VETRAN (May 21, 2009)

*I will add back freon*

I will add back at 2500 RPM slowly tonight and give update. Thanks


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## VETRAN (May 21, 2009)

6:00 Pm temp. 92 100 psi low & high before starting. Start and low drops to 5 psi low & 150 high. Start and adding can of r134a & see it rise to about 50 low side while adding freon. After adding about 1/2 can feel of cabin and not any cooler? did it leak some? Added the rest of can because when I closed the low side it droped to about 15 psi. After running about 10 min. low= 25 and high = 200. I drove it around about 5 min and no better. I forgot my thermometer but, feels about like 75-80 output. I am confused. I have the oil with yellow florecant dye so I looked for leaks around the pump and several places nothing visable? Tonight I will use the ultravilot light & look for any leaks anywhere and ck temp. again. Thanks for continued onging unending help. Again I have more time than money...


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## VETRAN (May 21, 2009)

10:00 PM I bought a new thermometer and found 10-14 degree from my old therm. Driving & fan on high center vent cycles down/ clutch engages in and out every few minutes as low as 58 degrees to 64, not bad. I will try again tomorrow in 95 degree heat and ck pressures. I found no new leaks with ultra vilot lights. I need to find a good oil/dye cleaner to remove stains from all the old leaks I repaired.


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## smj999smj (Jan 1, 2006)

A good running system will usually put out in the high 30's/low 40 degrees, of course ambient temperature and humidity play a part in that. You want to see that low side closer to 32 psi. Also, test with the system in recirc mode.


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## VETRAN (May 21, 2009)

Yes always Recirc mode,Vehical was gone last nite, I will retest tonight.


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## VETRAN (May 21, 2009)

*Fri. Even. 9:00 PM*

Outside temp 83 PSI = 95/95. Start with AC on psi goes to 0 / 125 and vent temp output is 80 degrees. After 4 min psi = 10 / 150 and 7 min =70 degrees. 12 min = 18 / 160 psi & 64 degrees. Test drive 5 min with output is 68 degrees and stop psi = 25 / 150 & 68 degrees.Fan always on high & recirc. next clutch kicks out psi climbs to 45 / 180 then drops to 20 /190 & 60 degrees in 30 seconds. Start driving again and vent temp climbs to 68 degrees again. Stop and ck = 24 / 160 then slowly climbs to28 / 175 and 56 degrees another min = 20 / 170 next =17 / 160. Clutch kicks out climbs to 35 / 160. Clutch in = 15 / 160 and 56 degrees then climbs to 45 / 120....56 degrees. I lost a ounce disconnectig the high pressure ga, hose. What next a little more freon? or wait and try in 90 degree sun?


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## VETRAN (May 21, 2009)

Only 85 today, Maybe Monday will be warmer to ck. again


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## smj999smj (Jan 1, 2006)

sounds like you let too much freon out.


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## VETRAN (May 21, 2009)

Update: 7:13 PM 82 degrees before starting = 95 PSI. Start = 96 degrees at vent psi goes to -2 / 130 psi. after 90 seconds = 5/150 After 2 min. = 12/158. 3 min. = vent 75 and 12 / 158. 5 min. 73 degrees at vent and 13 / 155. Time to add freon 1/2 to 3/4 of 12 oz. can 8 min = 60 degrees at vent and 30 / 200. add rest of can and 10 min. = 38 / 285. 15 min = 56 vent and 42 / 295. All looks good and will try next couple days in more heat and see if I loose freon / leaks oil etc.


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## VETRAN (May 21, 2009)

TEMP OUTPUT OK , I WILL HAVE THE VEHICLE TONIGHT TO CK PRESSURES.


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## VETRAN (May 21, 2009)

6:45 PM Fri. 85 degrees outside 97 degree cabin temp. 103 psi low & high before starting. 1 min. 15/155 & 75 degree at vent. 3 min = 20/ 250 70 degree vent. 4 min. 25/285 & 65 vent. 5 min 35/310 56 vent. 8 min. 40/325 10 min. 45 low peak and high fall back to 295 psi. I guess it is starting to cycle. No squeels. If I have leaks they are small so I maybe can let it go till cool weather. Thanks for everyone's help.


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