95 Camry Air Cond doesn't work occasionally

[ianm]

I have a 95 Camry. Recently recharged (1st ever after these years). No leak. Most times, air cond works beautifully.

Occasionally, after sitting in the sun for a couple of hours. air cond would not work. Compressor simply does not cut in. Then cool the car for a few hours, everything back to normal.

One repairman, after thorough exam and recharge, claimed that I had a blocked evaporator and needed replacement. I can't be sure he's right since air cond works most of the time. If I shade the windscreen on hot days, things are better - less likely the air cond will not work.

My uneducated guess: there may be a sensor in the Camry, which controls the cut in of the compressor, stops working under the heat of the sun. But that is just a shot in the dark. Can some knowledgeble poster tell me if I'm on the right track. If yes, what sensor is it?

[Camrymatic]

Does the AC light blink? Also does it stop working after a little while, like you drive on street for abtou 15 min and it cuts off, then you turn it on again later and it works again for about 5 min until the light starts blinking again and it turns off.

[davemac2]

I assume the sun shade screen helps keep the car cooler which helps the a/c 'seem' to be better. Are you sure the A/C clutch is not engaging when the A/C is on? If it isn't, then either your freon charge is gone or it is overcharged and during hot days, the high pressure switch is cutting out the compressor. Who charged your A/C?

davemc

[ianm]

Answer to questions of two preceding posts:

1. The A/C light did not blink. BEFORE A/C recharge, on a hot day (35C+), it could work for half an hours and then no. Normal function resumed after the car is completely cooled.

2. Sunshade did not create the illusion that it was cooler. The cool air (very cold) from the vent definitely was from A/C and I could hear compressor cutting in and out. I don't think it was an overcharge problem either as the same problem occurred before recharge, The guy who did it operates a qualified shop - one that's is recommended by the local Nissan dealer. So he knows his stuff. He's the one who diagnosed the evaporator blockage, but I just want a second opinion to allay my uncertainty.

[marc780]

This might sound lame, but try blowing out the fins on evaporator /and condensor with low pressure air? Question, If it were blocked would it not malfunction all the time...?

Also you may have gotten an overcharge on the refrigerant, if you hook a refrigerant gauge up to it (walmart has em actually) you can read the pressure (instructions on the package of the gauge) and this will tell you if your charge is correct.

[d0rkiishchris]

Originally Posted by Camrymatic

Does the AC light blink? Also does it stop working after a little while, like you drive on street for abtou 15 min and it cuts off, then you turn it on again later and it works again for about 5 min until the light starts blinking again and it turns off.

what does it mean when it does? Mine does when it gets wet. My theory is that the belt is in need of replacement.

[toyomoho]

Installing a pressure gage manifold and seeing what the readings are will check evaporator valve function. If a temp sensor, it should react pretty fast to temperature changes. As such once the cars interior is cooled down, so should the sensor. The compressor has both high and low pressure cut out switches.

[ianm]

[quote=marc780] If it were blocked would it not malfunction all the time...?

That's exactly my doubt when I was asked to have the evaporator replaced.

I still hope someone could answer this question: is there some kind of sensor(like a thermostat) which controls the cutting in and out of the compressor? If yes, what is the best way to test it?

[Camrymatic]

Your problem seems to be different from mine. My AC was blinking and the washers around the spinning part on the compressor locked up one day causing the serpentine belt to tear. Anyway, I got stranded between Orlando and Tallahassee, it sucked. Your problem could be different in nature, but I would check out the washers around the spinning wheel on the pump and make sure they are ok before it locks up.

[davemac2]

I can understand you second guessing the diagnosis since it is very expensive and labor-instensive to replace the evaporator usually.

I would think a blockage in the evaporator would reduce the efficiency of the A/C overall, so you would notice poor cooling as soon as you turn it on. If you have ever used a sealant in this system, then sometimes you can get a blockage that floats around a bit and eventually causes the high side of the system to exceed the high pressure cut-off switch and shut down the compressor. If this is the case, then after a few minutes, it should come back on again.

If you are saying the compressor is actually cutting out when your cold air stops and never comes back on until the engine itself has cooled, then it may have to do with the ECM cutting it off if it detects an engine overheating condition. It does this on some cars to provide more cooling capacity to the radiator to prevent an overheat. It can be due to a weak water pump, blocked radiator, dead or poorly running radiatot fan, head gasket leak issue, etc. Before the A/C cuts out, what is happening with the engine temp gauge? Check the rad fan and shroud as well, and look for anything sucked up between the condenser and the rad or in front of both.

davemc

[ianm]

[quote=davemac2].. blockage in the evaporator would reduce the efficiency of the A/C overall, so you would notice poor cooling as soon as you turn it on.

But it works beautifully when things are normal, and that is most of the time.

Originally Posted by davemac2

.. what is happening with the engine temp gauge?
It's normal.
davemc

Thanks for your detail reply. I do suspect something under the dashboard was mishaving, since shading the windscreen was a big, big help. Not being technially saavy (but just wanting to know more about the situation before bringing the car in for repair), I want to know what "sensors/controls" are located behind the dash.

[davemac2]

If you have a digital temperature A/C control head, then yes it is possible that is malfunctioning and not allowing the A/C to come back on since it would have one or more cabin temp sensors. You may want to pull the connectors from it and re-seat them to see if it helps (ie. oxidation on connectors). If you have a simple head which is basically fan control and vent slider, then the only other sensor in the interior may be a temp sensor at the evaporator to prevent evap freeze-over in cases where air flow is low for an extended period of time. For a simple head, the A/C compressor normally cycles on/off based on the low pressure cutoff switch on the low line side depending upon heat load in the cabin. The A/C expansion valve attempts to maintain an optimal evaporator temperature of near 32 deg F as best as possible by regulating freon flow into the evaporator. With a digital A/C head, it adds an extra on/off A/C clutch control via a cabin temp sensor to more cloesly regulate temps.

IF you want to troubleshoot this, you should get the schematics out of the service manual and familiarize yourself with the wiring to determine what exactly is disengaging the A/C clutch. When it happens again, you can eliminate the A/C head if you install a temporary switch in the circuit such that you bypass the A/C head and force its output to turn on the A/C and see what happens.

cheers,

davemc

[marc780]

A last ditch low-buck fix, ou could run wiring straight from the a/c switch (or the fuse connector at fuse box for same), to the compressor connector. And cut the smog switches etc, out of the loop. Probably not a trouble-free fix but in my happy ignorance, i dont see why you could not do this. Feedback anyone?

[indomla]

Originally Posted by Camrymatic

Does the AC light blink? Also does it stop working after a little while, like you drive on street for abtou 15 min and it cuts off, then you turn it on again later and it works again for about 5 min until the light starts blinking again and it turns off.

Sorry to resurrect an old thread, but my car has been doing this lately. The car is garage kept and as long as it is in the garage and not in the sun there appears to be no problems. If the car sits out in the sun (Houston sun is hot and humid), then the AC light (button) blinks and blows warm air. But after about 10 minutes of driving the AC blows cold air again.... Any help on what this issue is would be of assistance. Thanks.

[indomla]

nobody?