So I have a 04 tsx 2.4L and the low pressure keeps freezing.
I changed the expansion valve, evaporator, condesor, and the a/c compressor,

I've been trying to find the problem on why the pipe keeps freezing. Anyone have any ideas?

 

Does the air still blow out cold? Have you tried hooking up some gauges? What are the low and high pressure readings? Where exactly on the low side is it freezing? Don't just throw new parts at it try to find the problem first. Might be your thermo switch thats not turning of your compressor.

 

Too little refrigerant will cause localized freezing of the lines, indicating an undercharge condition.

What are the pressures before and after the freezing occurs.

 

Have you checked the A/C thermostat, if stuck on, it would not cycle the compressor off when evaporator temp. gets close to freezing.

Does your car have a "Cabin Filter", if so, have you checked it, restricted airflow through evaporator will cause problems. 94

 

a lot of good potential diagnoses in here.

had any other services before this started occuring? or repair work?

that's an expensive list of parts there.. can't believe you didn't actually diagnose this before replacing things, that or raise hell with the shop that started blindly throwing parts at your car with your money.

 

first and foremost: you mean internal freezing of the low side pipe correct? freezing of moisture on the exterior of the pipe is normal on the low side. if the ac is working but there is some frosty stuff on the pipe thats no reason to replace any parts, it means its working good.

now moving on to an internal freeze:
was it a new compressor and new condenser you used to replace? early model tsx's had problems with the compressors freezing and blowing up. the dryer is integrated onto the side of the consensor, if it was a used unit, its trash from being exposed to atmosphere, dryer becomes useless.

next: THE MOST IMPORTANT THING WHEN REPLACING COMPRESSOR. the correct amount and correct type of PAG oil needs to be added to the compressor.

..AND whenever you have the ac system opened up for a repair it needs AT LEAST 30-45 min. of vacuum before charging to remove any moisture that has entered the system. moisture is what freezes!

 

External freezing is not normal, it indicates that there is a lot of gas refregerant on the low side, if it were full of liquid, it would not freeze because of the extra mass flowing in the tubes preventing a large temperature drop. (IE freezing) This is caused by undercharging.

Again, what are your pressures at idle and off idle (1500-2000)

 

I think he (lassek20) may have meant if there is frost on the line it is normal. It is.

 

Frost on the lines is not normal under any conditions, it indicates a lack of refrigerant charge or poor airflow over the evaporator.

 

this. cool condensation is normal. but frost? your evaporator shouldn't even frost over under normal operation.

 

Exactly, condensation is completely normal, frost of any kind will eventually ice up the evaporator, rendering it useless.

 

While A low charge can cause frosting on the liquid line on some expansion valve systems with the right temperature and humidity,frosting can also form from a malfunctioning low pressure switch.


Lack of airflow thru the condenser will not cause this, nor will lack of airflow thru the evaporator. Frosting on the lines also
does not necessarily indicate an evaporator that is icing over(just clarifying)

With that said ,much depends on system design, txv or o tube, heat load available, and relative humidity along with ambient temp. So I suppose I should clarify and say that frost is normal on some systems during some circumstances.


It does not necessarily indicate a problem. Also, when I say frosting, I mean some frost on the line. Not a line that is completely frosted over.

 

Frost will always build up if the blower motor is not blowing air over the evaporator given an undercharge condition, think about it...

Frost on the lines post the expansion valve will eventually freeze the evaporator, as there is no heat to prevent it, it will ice up.

If the low pressure switch is malfunctioning, it doesn't matter. The switch does not prevent the system from icing up. All the switch will do is cycle the compressor to keep the system from freezing, it doesn't deal with the root of the problem. Which is obviously mechanical.

Frost is never normal for any A/C system in a vehicle, period. And please don't chime about reefers, totally different system.

 

Ditto the above frost on lines is not normal, [but can happen on low side, suction/vapour] line, if it happens on the high side, liquid/discharge line(s) you have a big problem.

EG; I have a late model Dodge Ram 3500 in the shop right now, the low side, [suction line and accumulator will build up some condensation on the outside when A/C is first turned on, it will freeze for a min.,[+/-] when humidity and ambiant temp. is high and then "melt" as A/C system gets up and running, after that it is just condensation.

To be clear, the low side line, suction/vapour does not have liquid in it it has "vapour", if there is liqiud in the suction line you have a big problem, the A/C compressor does not "like" liquid going into it.

The discharge line, [line from compressor to condensor] should be very hot, [full of compressed liqiud] the liquid line, [line from condensor to evaporator, expansion valve] will be hot, [not as hot as the discharge line] also full of liquid, the suction line, [line from evaporator/expansion valve] should be cold, this is the line that can "frost up" on the outside, as mentioned, ambiant temp. humidity will have an effect.

Also as mentioned, frosting/iceing lines is almost always an indication of a problem, particularly if it persists.

With that said, OP needs to clearify where/what is freezing, where on the "low pressure pipe" is it freezing?

As mentioned a manifold gauge set is need to see what the low and high side pressures are.

What was the refrigerant charge?

It's a little confusing, sevice manual says 1.1-1.2 lbs , [17.6-19.2 ozs] owners guide says 1.56-1.69 LBS, [24.96-27.04 ozs] that's quit the diff., we use 26 ozs as per our charge guide, the oil charge is 5 ozs PAG-46 oil or Ester oil, the correct oil charge is very important. 94

 

Agreed. But that was not what you said. You said frost on the line was an indication of a low charge OR poor flow over the evaporator. If the system is fully charged,but there is poor airflow across the evaporator, this in its self will not cause frost to form.

Incorrect. If evaporator heat load is lower to very low, or heat transfer is skewed due to some problem, the temperature of the refrigerant can go below 32 degrees causing any external condensate to freeze if the low pressure switch or cycling switch is not disengaging the compressor for the corresponding lower pressure due to the lower temperature of the refrigerant. In the aforementioned where temperature is lower and humidity is very low, frosting can occur.
Again incorrect. You seem to be unaware of the effects humidity,ambient temp and heat load have on this system. While you seem to have a good understanding of AC fundamentals, some of this systems idiosyncrasies seem to escape you.. Please take this as no disrespect, I continue to learn daily myself, but I encourage you to seek out what I have told here and verify the answers for your self. I assure you they are correct....




*And to be clear, I am only speaking of frost on the suction side*

 

First: I said given and undercharge condition.

Second: It still doesn't matter, the switch is not designed to control cooling, it is a safety switch, nothing more. The expansion valve will open more to increase low side pressure and thus keep the system from freezing. Orifice tube systems are the only systems utilizing a CCOT or Clutch-Cycling Orifice Tube strategy, because frost is more likely to form due to the way the refrigerant is metered (or should I say the lack thereof).

Third: You do not understand that any car A/C system should never operate below 35F due to freezing of the coil. This is well known. The only time a system will ice in normal operation is when it is designed to cool below freezing. In such systems the flow is reversed with the fans off, to heat the evaporator and remove the icing.

 

Ok. I suppose there is nothing more you can learn then..... However your understanding of the importance of the low pressure switch is flawed, I have dealt with and witnessed the issue of frosting on the lines personally as a result. Any one with at ounce of MVAC experience can tell you how a bad low pressure switch will affect the system. In fact, here is a trick that you or any one else reading this thread can do to prove it. Simply jump the low pressure switch and watch as the line begins to frost over.


No apologies necessary....

 

did you locate your freeze up

 

Will only frost if it is undercharged... I guess you will never learn, since that is the angle you plan to take. The low switch has nothing to do with icing, icing is a mechanical refrigerant problem. If the low pressure switch disengages the compressor due to freezing, that is the problem. Obviously the switch isn't the problem, it is a refrigerant or metering problem, why is that so hard for you to understand.

A condition of compressor operation is to have the low pressure switch closed anyways, so it is, in fact, normally shorted all the time. Which would mean by your understanding that every car should be icing up...... What?, are you serious?

 

So you will not be trying out what I told you? Instead you will stick with what you believe to be the answer. Its cool, you'll learn on your own when youre good and ready.....


Remember my words: "A bad pressure switch CAN cause frosting on the suction side because it is not cycling the compressor off by the cut point (usually 25 psi or so), with or with out a low charge."



I know you disagree, I just want that quote to be my final say on this matter.

 

I will pull a car or two aside and intentionally short the already shorted low pressure switch on some car, just to prove that irregardless of how the switch is shorted, it will still work the exact same way. My gosh I can't believe I am still going on about this lol.

You should really be asking, why is it getting cold enough to freeze (and thus need to cycle) in the first place, that is the point of this guys whole thread. Cycling is not normal for any expansion system, because the valve will control the cooling level based on sensing bulb temperature, preventing clutch cycling altogether.

I'm always willing to learn, only learning I'm interested in though is the right way.

 

^^This