Aircon fully gassed won't work !!! (1 Viewer)
- Thread starter Hillview
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Look for high and low static pressures to be 90-120 (depending on ambiant air Temps) can be higher. Then with compressor on the needle should be steady (no jumping around) high side should climb to 150 - 200 low side should drop to 20 - 30psi clutch should stop pressures equalize and then cycle again.
Cooling happens when the liquid refrigerant from the condenser goes through the expansion valve (3>4) and into the evaporator (4-1). Not sure where the XV is on an LC but there should be a noticeable difference there. As it travels throught the evaporator the liquid turns to gas. This is where it absorbs energy and cools the air. The XV senses the leaving evap temp so that the refrigerant is 100% gas before going back to the compressor. It will leave the compressor as high preussre hot gas (1>2) then gets condensed into subcooled liquid (2-3). A P-h chart for that particular refrigerant tells you the pressure and enthalpy (energy per kg). If all is working as it seems... its not the AC system. Here's a P-h chart for R-134a showing the refrigerant cycle...
1>2 is the compressor
2>3 is the condenser
3>4 is the expansion valve
4>1 is the evaporator (absorbs heat from the air)
Anyone feel free to correct me. It's been a while since I've designed refrigeration systems.
This will give you temps on the horizontal lines (inside the green line zones where its transitioning between liquid and gas). The horizontal lines mean saturated liquid/gas mixes which are alway at a constant temperature as long as gas and liquid co-exist.
The BTUs being pulled oout of the air depends on the refrigerant flow only. Temps and Pressures will all be the same regardless of system size.
Note that the enrgy required to compress the hot gas in the compressor is about one sixth of the energy removed from the air. The ratio of heat removed over the energy input is the refrigeration coeficient and is typically around 6-7.
1>2 is the compressor
2>3 is the condenser
3>4 is the expansion valve
4>1 is the evaporator (absorbs heat from the air)
Anyone feel free to correct me. It's been a while since I've designed refrigeration systems.
This will give you temps on the horizontal lines (inside the green line zones where its transitioning between liquid and gas). The horizontal lines mean saturated liquid/gas mixes which are alway at a constant temperature as long as gas and liquid co-exist.
The BTUs being pulled oout of the air depends on the refrigerant flow only. Temps and Pressures will all be the same regardless of system size.
Note that the enrgy required to compress the hot gas in the compressor is about one sixth of the energy removed from the air. The ratio of heat removed over the energy input is the refrigeration coeficient and is typically around 6-7.
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- Thread starter
- #24
Hi.... Thanks for your help and information with this as am somewhat baffled now!
Have check pressures again, the photos show the high side being 75psi ish static.
With compressor engaged per Manual, the high side rises to the higher number at about 1200-1400 rpm. The high side line to the condenser is hot from the comp fitting to the pipe joint.
Low side now differentiates by approx 5-6psi ?!?!?!? between static and Comp engaged per manual - lots of scratching head has ensued...... Temp is very marginally colder. The line on low side is warm.
Please let me know what you think as the manual I have is for. 2004 model and mine is a 2000.
The manual does say 650g +/- 50 with single a/c.
Have check pressures again, the photos show the high side being 75psi ish static.
With compressor engaged per Manual, the high side rises to the higher number at about 1200-1400 rpm. The high side line to the condenser is hot from the comp fitting to the pipe joint.
Low side now differentiates by approx 5-6psi ?!?!?!? between static and Comp engaged per manual - lots of scratching head has ensued...... Temp is very marginally colder. The line on low side is warm.
Please let me know what you think as the manual I have is for. 2004 model and mine is a 2000.
The manual does say 650g +/- 50 with single a/c.
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What are your pressure readings with the compressor running? (both low and high side).
With the compressor running....are you saying that your low side line is warm/hot to the touch?
With the compressor running....are you saying that your low side line is warm/hot to the touch?
- Thread starter
- #26
Hi
What are your pressure readings with the compressor running? (both low and high side).
- High when comp running is 90psi - Low side 84psi
With the compressor running....are you saying that your low side line is warm/hot to the touch?
- The High side Is Hot to touch
- Low is warm
What are your pressure readings with the compressor running? (both low and high side).
- High when comp running is 90psi - Low side 84psi
With the compressor running....are you saying that your low side line is warm/hot to the touch?
- The High side Is Hot to touch
- Low is warm
You have a restriction then. Most commonly at the TXV (expansion valve at the evaporator)
- Thread starter
- #28
Ive not looked at a TXV (expansion valve at the evaporator) Im guessing this has some kind of valve inside ? could that be stick closed ?
Is it difficult to rectify ?
Are there any other areas that could cause this effect ?
Is it difficult to rectify ?
Are there any other areas that could cause this effect ?
Yes, the TXV (thermal expansion valve) is just that. A valve that regulates the amount of liquid refrigerant entering the evaporator. It is the most common (though not only) source of restriction. It can stick open, closed or anywhere in between. It can also become clogged with debris in the system (desiccant, stop leak products, etc).
Your condenser could also have a blockage or restriction but the easy way to tell is to feel the high side line that goes along the firewall (small diameter line) while the compressor is running and see if that line is hot/warm to the touch all the way to where it joins the evaporator. IF it is...then chances are your condenser and those lines are fine.
Then feel the large line (low side line) coming out of the evaporator and if it isn't cool/cold then you've found your restriction (TXV or evaporator...or both).
The system has to been evacuated to perform any such repair (replace TXV or evaporator)
- Thread starter
- #30
thankyou for your help and guidance I shall check these areas on sunday and comeback.... thanks again
You'll typically see a vacuum on low side with expansion valve blockage, as the compressor pulls on the stuck valve or condenser it creates A vacuum..
Looks like your compressor is not working, you can try to add some refridgerant but I don't think your compressor can pump up enough pressure to see a reduction across your expansion valve.
Looks like your compressor is not working, you can try to add some refridgerant but I don't think your compressor can pump up enough pressure to see a reduction across your expansion valve.
If we see no changes in the high and low side readings when he adds refrigerant...we can pretty much assume the compressor is knackered (which generally results in both high and low side pressures being nearly equal).
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Agreed, if the txv is stuck open? I suppose it could result in similar symptoms. I've never seen it personally but plausible.
TXV is number one trouble spot in these systems. They stick, open, closed, partially open.....you name it.
- Thread starter
- #35
Hi all, its looking like it might be better to replace or rebuild most of this.
If I'm going to evacuate the system to change the expansion valve, would it not also be prudent to rebuild and recondition the compressor given some of the symptoms and your guidance ?
Valves seem to be relatively cheap.
Has anyone experienced a compressor rebuild? Can anyone tell me where I can get the needed parts from?
I haven't enquired as yet, but does Toyota do any form of rebuild kit?
I rebuilt porsche 928 compressors albeit 10 or so years ago... How hard can it be?!?!
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Agree with 'replace' I wouldn't try to 'rebuild' the compressor....unless the only thing needed was seals. Yes, I've done it before....and its high up on my list of things to 'never do again'.
The true condition of your present compressor will dictate whether or not replacement of other items (Evaporator and Condenser) would be wise (you can't adequately flush these to remove metal particles). A re-manufactured Denso compressor would be the way to go for a replacement.
Your high and low side pressures rather suggest a compressor that is worn and not able to 'compress' the refrigerant in its gaseous state (similar to blow-by) in a engine cylinder. As such...the readings are very often like 'static pressure' (nearly the same both high and low). Certain restrictions (depending upon where they are and how severe) can mimic this.
It would be helpful to know the history of the system also. What prompted you to service the system to begin with? When was the last time it worked properly. Did the condition that caused you to service it come on suddenly or has the system been in need for some time?
I realize that in your climate....the A/C is not needed as often....so perhaps these questions are hard to answer.
- Thread starter
- #37
HI,
I think I have tracked down some compressor parts in Holland so I can rebuild my A/C pump... no one in the UK that I found seemed to have anything on the shelf.
I shall let you know the status of parts supply !
Eyedaho
SILVER Star
I believe that my AC compressor is on the way out, and I'm getting ready to replace it. When the clutch engages it gets very noisy as though something is failing internally, although my AC blows very cold. I have a new Denso compressor, a new dryer on the way, and a vacuum pump with manifolds. Reading through a bunch of posts, it sounds like I may want to replace the TXV at the same time. I have two questions that I'm hoping @flintknapper might be kind enough to answer for me. The first is how accessible the front TXV is on a 100 series. Looking at the parts drawing, it appears to be buried in the dash behind the evaporator. So, I'm not sure if it's worth it to try to replace it? My rig is a '99 with >300k, so if it's a failure part then it might be worth it? That was my first question. 
My second question is if there's a difference between 8851560110 and 8851548010? Partsouq shows them both for my VIN, and not in their typical supersession kind of way.
Thank you in advance for any insight!
My second question is if there's a difference between 8851560110 and 8851548010? Partsouq shows them both for my VIN, and not in their typical supersession kind of way.
Thank you in advance for any insight!
Eyedaho
SILVER Star
I was able to find the location of the expansion valve in this post:I believe that my AC compressor is on the way out, and I'm getting ready to replace it. When the clutch engages it gets very noisy as though something is failing internally, although my AC blows very cold. I have a new Denso compressor, a new dryer on the way, and a vacuum pump with manifolds. Reading through a bunch of posts, it sounds like I may want to replace the TXV at the same time. I have two questions that I'm hoping @flintknapper might be kind enough to answer for me. The first is how accessible the front TXV is on a 100 series. Looking at the parts drawing, it appears to be buried in the dash behind the evaporator. So, I'm not sure if it's worth it to try to replace it? My rig is a '99 with >300k, so if it's a failure part then it might be worth it? That was my first question.
My second question is if there's a difference between 8851560110 and 8851548010? Partsouq shows them both for my VIN, and not in their typical supersession kind of way.
Thank you in advance for any insight!
AC issues, can't figure out.
so that's what that is....:doh: I was looking at condenser replacements and thought "what a weird shape!"
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