OT: a/c problem on 1999 ford taurus

[ryan roopnarine]

about 6 months ago, I put a cheapo lo pressure gauge to a semi-lukewarm a/c system and found the compressor cycling between 32 and 37 every 10 seconds or so. this is with the a/c on full blast and the gauge hooked up. even without the gauge on it, it would cycle really often. right now, i'm not getting any cold air out of it at all. is this a pressure switch issue, or something else? thanks for your guesses.

[Tiger]

Without the compressor running, the system must have around 60 PSI to run. However, I suspect your system is filled with mostly air. You must vacuum it out and reinject it with R134a.

Sure, you can have system runing at 35 PSI but very little refrigerant in the system.

Autozone loans out vacuum pump for free. See what the sticker in the hood area say how many oz. your system takes.

[bsell]

Without the compressor running, the system must have around 60 PSI to run. However, I suspect your system is filled with mostly air. You must vacuum it out and reinject it with R134a.

Sure, you can have system runing at 35 PSI but very little refrigerant in the system.

Autozone loans out vacuum pump for free. See what the sticker in the hood area say how many oz. your system takes.

True enough that the original freon is missing now, causing low pressure in the system. I don't know that 'air' got back into a system that is above atmospheric pressure...

Your low pressure switch is working, turning off the compressor to save itself from lack of oil flow (rides with the freon...which by the looks of things, is in short supply).

I figure your freon leak is in the high pressure side, typically the hose from compressor to the condensor. Hopefully your compressor seal isn't leaking. Of course any of the o-rings at the pipe junctures could be old and cracked...

Get hold of a freon leak detector, find the leak while you still have freon in the system, then do the fix/vacuum/refill. If you break into the systems integrity, spend the cash for a new receiver/dryer in addition to fixing the leaking part. The receiver/dryer is also the 'filter' for the system and can get clogged with compressor stuff over the years, restricting freon flow which reduces the A/C's power.

Best of luck,

Brian

[Tiger]

The compressor is a pump so it will suck in any air wherever the leak is. Anyway, it is not all air... just majority air. I have seen quite a bit of cars that came into my uncle's garage with some pressure but when we evacuated the system with the AC machine, it revealed nothing recovered or like 1 oz. which is nothing compared to 20+ oz most cars need.

[ryan roopnarine]

i attached a manifold gauge set and took some readings on it:

static (after the car was shut off):
high 92
low 93

temperature outside was 89 degrees farenheight.

running (the compressor was engaging for 3 seconds on, 3 seconds off)
high 140-155
low 22-42.

anyone wanna guess.

[Tiger]

The low and high pressure is right... I am guessing you got too much refrigerant which triggers the high side cutoff when it hits 42 PSI. If you don't mind, let some pressure out when the system is off... let it go down to 85 PSI static.

Low should be rock steady at 28-30 PSI.

Your compressor is working properly.

[bsell]

i attached a manifold gauge set and took some readings on it:

static (after the car was shut off):
high 92
low 93

temperature outside was 89 degrees farenheight.

running (the compressor was engaging for 3 seconds on, 3 seconds off)
high 140-155
low 22-42.

anyone wanna guess.

Those numbers are low, especially the high side for such a warm day. This most likely means low freon level. I figure a low side of 35-45 w/ high side of 250-325 is about right...

What did the sight glass look like while the compressor was running? I figure very frothy...on a 'solid' system, it should be solid liquid only.

I take the rad fans were running? Or do they cycle with the compressor? Either way, once you get the system to hold freon, ensure the fan(s) run with the compressor.

Brian

[Tiger]

Good point about the aux fan... it must be running when AC is switched on.

For R134a, you want the low pressure to be 28 to 30 PSI.

[ryan roopnarine]

1 evacuation and one vacuum later...
system holds between 29-30 inches HG over 17 hours. the drop might be because i disconnected and reconnected everything.

in went one 12oz can of leak detector r134a
1 2/3 can of regular freon (capacity is 32oz/.96kg)

about 90-94 deg f today, it feels cold, but as though something is missing. i only noted that the engine fan came on with the ac, i don't know if there have to be special circumstances for the other fan to come on.

reads 42lb low
and 230 high. don't want to overcharge the thing, because i don't have a refrigerant scale. should i try to fit the other can in?

thanks for your help.