1995 R134a air-condition malfunction

Hi, have my camry air-condition compressor shutting off itself occasionally. Then turning itself back on...

Probably due to some shut-off switch - the lamp on the a/c button blinks. Is there a way to tell which switch caused the compressor shut down ?

I have tested pressures with gauges and got about 20psi on the low side - sometimes dropping to 10psi on cold system and above 150psi on the high side... I feel it is little bit too low on both sides, but not sure. What is the proper pressure for that camry?

I see some bubbles in the sight glass, but I remember seeing them even when the system was fully charged and was working very efficiently blowing 40F air.

Now it is still cooling when compressor is on, but not so good - the vents are blowing about 60F air...

Also noticed that on previous service belts were exchanged and the alternator/compressor belt was streached to hard, causing the compressor wheel to turn slightly even when the compressor clutch was not engaged. I made this belt little bit more loose but the compressor still shuts off itself...

Any diagnostic advice appreciated!

Reply to
Pszemol
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Reply to
johngdole

Yes, I was... Yesterday evening I got one 12oz can of freon. Tried to recharge gas, but it went very slow... Could not fit the whole can. The pressure rise to 26/205 - temperature is back to

Reply to
Pszemol

You don't want to put too much freon into the system. I had my at

35/230, at the upper range, during 90F outside air temp.

Sometimes extremely low low-side pressure is because the expansion valve is stuck and the compressor will cycle on and off all the time. But from the looks of 205 that's not the case.

Most of the time I charge a few ozs, never charged more than 6oz or 1/2 a can for a long time. There will always be some left because the low side never gets below say 25-30PSI. It would start fast and then slow down quickly. It helps to wrap a warm towel around it. It will also help if someone revs the engine at 1500 rpm. That should be where you check the pressures anyway (do check the rev specs for 95!).

Pszemol wrote:

Reply to
johngdole

So I have still room to put more. BTW-I still see the bubbles in the sight glass.

I have the feeling the compressor is actually cycling on and off. Like it would prevent from freezing. The temp at the vents drops below 40F and then goes up over 40F and the cycle repeats. Do you think something is wrong with the system ?

If I look at the working system compressor wheel and see the clutch engaginh and disengaging cyclicly - that would be bad? I need to do such experiment.

How long (in minutes) does it take to suck a half bottle of freon 6oz for you? Anyway - I can rev the engine up from under the hood just by pulling the trottle cable. It is located on top, above the valve cover/air intake.

Reply to
Pszemol

Have a look here:

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See also around page 25/26 or so - "Insufficient Refrigerant", "Poor Circulation of Refrigerant".

Have fun, take safety precautions...

Michael

Reply to
mrdarrett

Your system sounds normal, actually. The modern system's compressor should cycle on and off and let the liquid freon work through the expansion valve. According to Haynes manual, you are getting it down to

40F (or generally 30-40F below ambient in hot weather) you should be OK.

But it's a good idea to check the evaporator drain valve to make sure it's not plugged by spiders, etc. So the moisture can drain out.

When the system in not operation, the equalized pressure (measured at Low side) should be around 60-90 psi. Measure this overnight. Overcharging is not good, probably worse than undercharge. Other than this, the home mechanic can do very little. When it doubt, it's better to take it to an AC specialist.

I never clocked it, but I don't think it took more than 10-15 minutes. A few repeats of warming it up, reconnecting, and charging until it reached 35 PSI.

Check out the AC system FAQ and How-to Videos at Interdynamics:

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Reply to
johngdole

But still it does shut itself off from time to time and the lamp on the A/C button blinks then. When I turn the button off and then on after a minute or two, a/c works as normal, untill it shuts off itself again...

Moisture drains very well... I have wet puddle under the car after parking.

I could place the can on the exhaust sheild :-) The hose from the can is long enough :-)))) That would keep it warm ;-)

Thanks everybody. I downloaded the A/C repair manual too... Need to study it a little and maybe I will find out how to diagnose it shutting off on its own.

Reply to
Pszemol

Well, you've already charged pretty much a can. If it still is giving you problem, it's time to take it in to an AC specialist or the dealer to read off the diagnostics code in the AC controller. Don't charge any more freon. I don't think the previous mechanic who over tightened the belt should be whom you visit.

Reply to
johngdole

The previous mechanic was a toyota dealership :-)

I went to the same place and ask them how would they deal with an intermittent problem like this. If there are some error codes stored in the computer they can read... I got the response that the A/C system is not recorded in the ECU so there are not codes stored there to read. I would have to bring the car in when it happens in order for them to look at it.

The problem is that it does not happen often, so the chances are that I bring the car for the diagnosis just to find out that at this particular moment everythis was perfectly fine with it :-) He said it could be the compressor clutch, pressure switch or the A/C control unit itself - and they will not be able to tell what is wrong until the problem would present itself.

Not sure what to do after hearing this story at the Toyota.

I am tempted to hook up some indicator lamp to several sensors and observer their operation during driving :-))) Any ideas what to look at and how to hook up some indicator light?

Reply to
Pszemol

%$#@ ! That's really too bad. We all share experiences about how the misfits and drop-outs don't follow Toyota's own procedures. Like I said, finding a good mechanic is tough. And as you learned, even at the dealer's service department.

I am glad I do all the routine maintenance and some repairs myself. The car will sure last longer than if the dealer had maintained it.

The AC control unit doesn't store OBD style codes (ex. P0420). Some models with climate control units would give you two-digit codes on what the problems are: for example, compressor, compressor clutch, clutch speed sensor, temperaure sensor, pressure sensor, etc. Many non-climate-controlled AC systems would give simple codes like mixer control motor, mode control motor, and evaporator temperature sensor by flashing the light once to three times. But Haynes only tells of what can be extracted with climate control units; maybe there is nothing the Toyota units will tell then.

Just some thoughts. With the proper Haynes or factory manual in hand, you can test the compressor lock sensor resistance by measuring (~60-120ohms, check your manual for actual spec values) and compressor clutch operation by supplying 12V/ground to the leads. These two are the two pairs of wires on the connector near the compressor. Energized clutch pressure plate and rotor should have the right clearance, about .5mm. The clutch hub and other pulleys should be properly aligned. Is there signs of corrosion at the connectors?

Is the AC/Alt belt glazed? If your compressor is seizing the belt would likely glaze as it slips in the clutch pulley. I recommend a Gates Krikit belt tension gauge, available at your loca NAPA store ~$20 these days. The deflection method is really not very accurate.

When the compressor cuts off, you should have no continuity at the pressure switch. And normally you should see continuity. But I suspect the pressure switch is working as advertised. When the compressor cuts off, are you seeing 10/150? Do you ever see vacuum on the low side?

It may also help to learn the relative temperatures of the high/low pressure pipes. Do you see frost on the high pressure pipe? Do they get warm? The low pressure thicker pipe should be slightly cooler (3-10F) than the thinner high pressure pipe (should be cold).

Also, it's a good time to ask around for a good reference to an AC specialist.

Reply to
johngdole

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