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2001 Pontiac Sunfire low air flow from vents

Tiny
WVPHYSICS
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  • 2001 PONTIAC SUNFIRE
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 107,000 MILES
Sometimes it seems like the air flow from my vents is restricted, more so after the a/c has been on for some time. I suspect the evaporator is freezing up, but the dash needs to be removed to look. The low pressure line does develop some frost. I took pressure readings, upon starting the car it was about 35/175 psi and after about 15 minutes was at 30/155 psi (high side seems a little low to me) at 80F ambient and about 60% humidity. This was with max A/C and blower at max. The temperature at the vent, using a digital meat thermometer, can get down to 28F (seems like that temperature should be closer to 32) if the fan is on low, or the low 30's if at higher settings. I had a major leak a year ago and replaced compressor, accumulator, and orific tube. I evacuated, purged the transfer lines, and filled with the 1.5 lbs recommended weight. I figure the possible causes are low refrigerent, dirty evaporator, or I have heard maybe air in the lines. I have wondered about some sort of switch that is supposed to turn off the compressor automatically, but I am not sure if 2001's had that. Any thoughts? I'm experienced enough to know some of the details of normal funtion. I usually throroughly research it, but some of this is hard to find for sunfires.
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Wednesday, June 29th, 2011 AT 1:49 PM

16 Replies

Tiny
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Should cycle off at below 35 so suspect A/C pressuer switch located in high side line from COMP to COND next to high side service port
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Wednesday, June 29th, 2011 AT 2:23 PM
Tiny
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I couldn't find anything about an AC pressure switch online or in the haynes manual, so I wasn't sure if there was one. I think I know where it is, I recall often wondering about something near the high side connetion. Do the the numbers from the pressure guage and temperature seem to be within normal operating range?
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Wednesday, June 29th, 2011 AT 2:32 PM
Tiny
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Yes
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Wednesday, June 29th, 2011 AT 2:40 PM
Tiny
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Except for 30/155 the 35/175 is dead on
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Wednesday, June 29th, 2011 AT 2:42 PM
Tiny
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Thanks, for now I'll keep an eye on the pressures and try to find a new switch.
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Wednesday, June 29th, 2011 AT 2:44 PM
Tiny
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Am I correct in assuming that replacing the switch will open the system, so the refrigerant will need recovered then recharged?
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Wednesday, June 29th, 2011 AT 2:50 PM
Tiny
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Nope switch is screwed onto a schrader valve no need to discharge
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Wednesday, June 29th, 2011 AT 2:53 PM
Tiny
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Thanks, I think I found the switch on NAPA's website too. I'll try that and repost if I still have issues.
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Wednesday, June 29th, 2011 AT 2:54 PM
Tiny
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O.K.
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Wednesday, June 29th, 2011 AT 2:59 PM
Tiny
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I was going to get a switch until I stumbled onto a few posts that say the V5 compressors that the sunfires use do not cycle, they remain on unless the high pressure side gets too much pressure or way too low to operate. This would make sense since the switch is monitoring the high side instead of the low side where the evaporator is. The evaporator freezes before the high side pressure gets low enough for the switch to shut off. Can anyone confirm this for 2001 sunfires in particular? If it is not th switch is the next likely cause low refrigerant?
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Thursday, June 30th, 2011 AT 5:04 PM
Tiny
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Correct but switch is a dual low/high
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Thursday, August 11th, 2011 AT 3:46 PM
Tiny
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Wvphysics (and Docfixit) -- this thread is the closest that I've found to the problem I'm having with the used '00 Sunfire that I just purchased two weeks ago.

The A/C is ice cold, but after running continuously in the mid-Florida heat/humidity for a period of time (perhaps 20-30 minutes) the strong flow of air from the vents dwindles down to next to nothing (albeit still cold). Turning the fan to the highest speed at this point results in an abnormally loud grumbling from the blower motor (or whatnot) on the passenger side of the vehicle, without much of any impact on the outflow.

I popped open the engine during such an occurrence and noted thick amounts of ice had developed on the lines, but little else (as the bulk seems quite concealed).

If the A/C is shut off (even with fan still running) within a handful of minutes the airflow is again restored, and the A/C can be restarted until it dwindles again. It's almost as if the blower is getting locked up with ice, then melts, then gets locked up again.

I suspect we're having the same problem. Perhaps we can troubleshoot this together? I'm afraid I certainly don't have the diagnostic equipment or knowledge that you seem to be able to tap into, but I'd like to ride on your solution if you don't mind.

Cheers,

Craig
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Friday, August 12th, 2011 AT 11:28 PM
Tiny
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BTW - for what it's worth, I've got the records from the previous owner, and there has been work done to the A/C:

March 11, 2011:
REMAIN. A/C COMPRESSOR, R-134A REFRIGERANT
R&R ALL ASSOCIATED PARTS, FLUSH SYSTEM, EVACUATE & RECHARGE A/C
$380.01
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Saturday, August 13th, 2011 AT 12:14 AM
Tiny
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Suspect orifice tube located in outlet line of condensor. Try this back off on temp setting to heat see if it stays blowing and no icing of lines. Don't suppose you have a set of AC guages?
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Saturday, August 13th, 2011 AT 4:45 PM
Tiny
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Just recently relocated to FL from years abroad -- I've scarcely got a socket set put together so far! Can supply a photo of the frozen lines, if that would be helpful.
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Saturday, August 13th, 2011 AT 11:45 PM
Tiny
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Could not hurt
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Monday, August 15th, 2011 AT 3:08 PM

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