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A/C problem- no cold air

B

BigRob

New CEG'er
Joined
Feb 18, 2007
Messages
17
Yes I have read the many post of take it to the shop If you dont know what you are doing, I agree, But I would like to learn something even If I have to take it to the shop anyways. So here goes.... Compressor was short cycling so I checked pressure with my manifold gauges, high side and low side were about even at 20 lbs.not good so I hooked up my vacuum pump and brought it down to about -28 to -29 lbs. Let pump run for an hour to remove any moisture. Closed gauges and checked to see if it held vacuum, it did for over an hour.So no leaks I hope.I hooked up can of R134a to middle yellow line, bled off air in line before opening low side of port to prevent air entrance into line. it took the whole can. Then I turned on car and added a second can and jumpered the low pressure switch to activate the compressor to pull in the second can. rechecked the high and low side pressures and now the are up to 60lbs. no change while running. So for giggle ,I hooked up one of those walmart guages and it went up and down like I suspected it would do while the compressor short cycled. So this is were I stopped And decided to look for advice here.:help: Any Advice would be appreciated.Thanks
 
You are a bit unclear.

You say: "rechecked the high and low side pressures and now the are up to 60lbs. no change while running. "

Then you indicate it still short cycles.

If it short cycles, then the compressor must be changing the pressures.

Are you using the gages correctly?

The low pressure cutout prevents operationwhen the low side goes under 25-27 PSI. This can be caused by low refrigerant level, poor evaporator response (no air over the evaporator), or blockage (frost in abnormal places).

Normal gage response is for the low side to pull down to ~ 35 PSI and the high side to rise to ~ 300 PSI depending upon ambient temperatures.
 
well thank you for reading the old post and using the correct tools and methods to work on the A/C system.

I am also alittle confused with your discription. If the compresor is short cycling then the pressures should still be changing. 2 12 oz cans is what you need to completely fill the system.

I have noted that the static pressure with the system off is low on the high pressure side and very high on the low pressure side. when properly filled the pressures will raise and fall when the compressor cycles. again the pressures depend on the ambient.


ok ... you said the cheap wal-mart guage was moving like it should with the compressor cycling and the guage set didn't .... are there any valves on the guage set that you didn't open?
 
The gauges were open at the service port connections and off at the manifold.(is this correct?)when I hooked up the gauges to my other car ,they operated normally, so that is why I hooked up the walmart gauge and it fluctuated with the compressor short cyling.I did add one of those pag oil charges between cans of 134a. I think I should have checked the orifice tube for blockages ,but I didnt have a springlock tool for it(my bad) when I had the system empty. Do you think that this would cause the described problem?Do you think I have added too much oil? I also did notice a slight leak at high side service port at that little black ball insert,what is the trick to taking these off without damage to the lines? I am sorry if it is a confusing post as I have been at this for awhile. I greatley apperciate your time for response.Thanks
 
Did it draw the 2nd can, if not, put R134 can in pot of hot tap water and fill it up until it "just" doesn't get colder at dash vent.
 
yes it will take what I put in it, but all that does is just push the pressure up. It still short cycles and doent get cold at all.Static charge is around 60 on both sides, When I turn the car on and read gauges it fluctuates 20-80 on low side and 150-200 on high side during short cycles. Everything that I read about short cycling would indicate a low charge. I even replaced the clutch cycling switch(low pressure switch) but no change at all to temp. Any Ideas?
 
If it drops below 30 PSI on the low side, compressor will cycle off. 20 is too low. Try adding a little more R134, should start to function.
 
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the manifold gauges are closed, the problem was they way the instruction manual said to close the port valves.It was the opposite way in order to get the gauges to read correctly.
I have not had anytime lately to continue working on car untill the weekend.will try again.
 
If it drops below 30 PSI on the low side, compressor will cycle off. 20 is too low. Try adding a little more R134, should start to function.


I did add more r134 but it just pushed the pressure up higher and did not stop short cycling. I 'm begining to suspect clogged orifice tube.will check this weekend.
 
...are you having a conversation with yourself????

I doubt you have a bad or restricted o-tube. From the coherent parts of your posts, I see only an undercharged system and a possible malfunctioning (or improperly used) manifold gauge.
 
no, I hope I'm not talking to myself. I wiil try this weekend and recheck my gauges to see if some thing is wrong with the gauges but I had 3 cans in and it still did not stop short cycleing. Thanks for the input. I appreciate your patience with my postings. Where you refering to my cut and paste From My Favorite Mystaque in the above post?:crazy:
 
Well the weekend is here so I pulled out the radiator and used a hose to blow out anything that accumulated on the condensor coil. There was alot of dirt and debris there. I also replaced the missing rubber strip at the top of the radiator and condensor coil that keeps the air from going out the top between the two. I replaced the fan resistor at the bottom of the fan shroud since I had the radiator and fan off(see my prevoius post on cooling fans awhile ago) I also replaced the wire harness that went across the fan shroud and hooked up to the a/c condenssor, low pressure cycling switch, resistor and ground in hopes this would restore my cooling fan.whew:eek: Ok ,after that I hooked up the manifold gauges and checked my static pressure and it was equal at 20 lbs, way low ( I must have a leak somewhere) compressor wasnt even cycling this time so I grabbed another can of r134 and and hooked it up to the yellow service port, opened can and bleed out air first through shrader valve on the service port tee. Then opened low side on manifold and fed the r134 into the system and watched the gauges climb. Compressor then started to shorrt cycle when pressure was increasing. I kept feeding can until compressor stayed on around 210 lbs of pressure on high side and low side stayed at about 30lbs everything looked good but still no cold air, then the high side started climbing up and up until the high pressure switch cut it off around 400-410.yikes:shrug: So what does this sound like? Just trying to figure out what direction to go and what next to check. Thanks again for your help.
 
the fan only came on when the coolant temp got to the "L" in "NORMAL" almost too the red. this also has me puzzled as the replacement of the fan resistor in the fan shroud was suposed to have fixed this issue but I guess not , now I have to figure out what sppeds the fan has...Hey favoritemystaqiue ,would you chat on yahoo messenger or any other messenger for guick response?
 
Fan does not come on with A/C then (even with the pressures in the system). If you jumped the pressure switch on the accumulator and turn on A/C, the radiator fan should run/compressor engages. If it doesn't I could refer you to the Fan test/schematics that are bookmarked on my Home PC, but not at work..
 
I did jump the switch and the fan comes on, and sometimes when the pressure was causing it to cycle it would operate intermitinley.I dont know if it was cycling too quickly for the fan to stay on constantly. When should the fan normally come on without the a/c on? I let the car get to the red to make the fan come on then I pulled the green relay to see if that affected operation and the fan turned off. I repeated the same proceedure and this time pulled the black relay out and nothing happened. I did not stop the fan. This black relay is suposed to be the high spped relay, does that mean I have a bad relay? Is there any way to test a relay?
 
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