Tired of AC Problems
- Thread starter bcossa2001
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Well, it died on me on the way home today. Ambient temp 83 degrees.
1500 RPM, full recirc, fan on high, blowing ambient air
compressor running full time
low side -20 (i.e. in vacuum)
High side 150
no change for several minutes....
1500 RPM, full recirc, fan on high, blowing ambient air
compressor running full time
low side -20 (i.e. in vacuum)
High side 150
no change for several minutes....
Originally Posted By: bcossa2001
Well, it died on me on the way home today. Ambient temp 83 degrees.
1500 RPM, full recirc, fan on high, blowing ambient air
compressor running full time
low side -20 (i.e. in vacuum)
High side 150
no change for several minutes....
No surprise there, what with leaky service port valves.
If you want to try replacing the valve cores:
You will probably need an AC valve core tool. Google it. Buy new valve cores from an AC/Radiator specialty shop if you can. Do not buy them from an auto parts store or a dealership unless you want to risk installing a brand-new-bad part. Before removing the core, clean the inside of the port thoroughly with compressed air or CO2. While the core is out you have a good opportunity to easily pour in a bottle of AC dye. Don't get the oil that has a little dye mixed in, get the tiny little bottle of concentrated dye. Lots of dye makes finding leaks easier. Lube the new core with refrigerant oil before installing it. After you install the new core(s), give the system a partial charge or helium charge and check for leaks by pouring refrigerant oil into the service port and looking for bubbles. No bubbles for 10 minutes is about good enough to do a vacuum and full charge.
Sometimes replacing a core won't stop the port from leaking. If a shiny new core that closes properly is screwed into a pitted or eroded fitting it may not seal. The bubbles will show you this. At that point you're going to need to replace the part that has the fitting welded to it.
Well, it died on me on the way home today. Ambient temp 83 degrees.
1500 RPM, full recirc, fan on high, blowing ambient air
compressor running full time
low side -20 (i.e. in vacuum)
High side 150
no change for several minutes....
No surprise there, what with leaky service port valves.
If you want to try replacing the valve cores:
You will probably need an AC valve core tool. Google it. Buy new valve cores from an AC/Radiator specialty shop if you can. Do not buy them from an auto parts store or a dealership unless you want to risk installing a brand-new-bad part. Before removing the core, clean the inside of the port thoroughly with compressed air or CO2. While the core is out you have a good opportunity to easily pour in a bottle of AC dye. Don't get the oil that has a little dye mixed in, get the tiny little bottle of concentrated dye. Lots of dye makes finding leaks easier. Lube the new core with refrigerant oil before installing it. After you install the new core(s), give the system a partial charge or helium charge and check for leaks by pouring refrigerant oil into the service port and looking for bubbles. No bubbles for 10 minutes is about good enough to do a vacuum and full charge.
Sometimes replacing a core won't stop the port from leaking. If a shiny new core that closes properly is screwed into a pitted or eroded fitting it may not seal. The bubbles will show you this. At that point you're going to need to replace the part that has the fitting welded to it.
Originally Posted By: 1 FMF
this is for your 97 toyota avalon correct?
you're either low on refrigerant or have a bad thermostatic expansion valve, known as TEV or TX valve. I believe these are more tolerant to overcharging than an orifice tube system, so you can add an 8 oz can of r134a and see what that does, worst case you get higher compressor head pressure (and lower efficiency) and you'll see that on your high side gauge but the TEV should regulate and give you cold consistent evaporator temps. If one 8 ounce can doesn't help then it's the TEV which is common. If you haven't touched it since the repair there's probably a leak, I would loosen then retighten in the valves in the ports. if they have plastic caps, listen for a little pssst when you undo them if so they are seeping and after a month it will be low and not blow cold.
The evaporator might also be a problem, because the expansion valve might be corroded and stuck the the evaporator. This happened to my father when he had his 1997 Lexus ES300.
this is for your 97 toyota avalon correct?
you're either low on refrigerant or have a bad thermostatic expansion valve, known as TEV or TX valve. I believe these are more tolerant to overcharging than an orifice tube system, so you can add an 8 oz can of r134a and see what that does, worst case you get higher compressor head pressure (and lower efficiency) and you'll see that on your high side gauge but the TEV should regulate and give you cold consistent evaporator temps. If one 8 ounce can doesn't help then it's the TEV which is common. If you haven't touched it since the repair there's probably a leak, I would loosen then retighten in the valves in the ports. if they have plastic caps, listen for a little pssst when you undo them if so they are seeping and after a month it will be low and not blow cold.
The evaporator might also be a problem, because the expansion valve might be corroded and stuck the the evaporator. This happened to my father when he had his 1997 Lexus ES300.
Ran static test this morning.
Low side 80 PSI
High side 80 PSI
Ambient temp 79 degrees...
I think I'm going to try a can of refrigerant and see what happens...
Low side 80 PSI
High side 80 PSI
Ambient temp 79 degrees...
I think I'm going to try a can of refrigerant and see what happens...
Yeesh, this is getting old...
Did not add any refrigerant yet...
Yesterday when it went out I had been sitting in traffic for 20 minutes..
Today I waited until I got on the interstate to turn it on..
Ran 20 minutes on the road--60 mph--never got above 50 degrees with 85 ambient.
Stopped, went into store for 10 minutes, came back out, stop-n-go traffic for 10 minutes...never above 51 degrees with 85 ambient....
I'll see how it goes next week. It is annoying I cannot seem to find a pattern. Makes me think something is working intermittently.....
Did not add any refrigerant yet...
Yesterday when it went out I had been sitting in traffic for 20 minutes..
Today I waited until I got on the interstate to turn it on..
Ran 20 minutes on the road--60 mph--never got above 50 degrees with 85 ambient.
Stopped, went into store for 10 minutes, came back out, stop-n-go traffic for 10 minutes...never above 51 degrees with 85 ambient....
I'll see how it goes next week. It is annoying I cannot seem to find a pattern. Makes me think something is working intermittently.....
It went out on me again today...
If I add refrigernat, does it matter if it is added when the system is cooling vs. when it is not cooling???
If I add refrigernat, does it matter if it is added when the system is cooling vs. when it is not cooling???
Originally Posted By: bcossa2001
It went out on me again today...
If I add refrigernat, does it matter if it is added when the system is cooling vs. when it is not cooling???
Yes. The low side pressure is what helps draw out the most refrigerant from the can.
It went out on me again today...
If I add refrigernat, does it matter if it is added when the system is cooling vs. when it is not cooling???
Yes. The low side pressure is what helps draw out the most refrigerant from the can.
Well it went out again today so I bought some refrigerant. Hooked up the gauges--Low side about -20 (vacuum) high side 125.
Verified that the compressor was running. Started letting in refrigerant, slowly, low side fluctuated from +50 to +40. No change on the high side. No cooling at all from the vents. When I closed the valve to the refrigerant the low side pressure went back to -20 (vacuum). High side up to 130. 12 oz. can of refrigerant empty.
????
Verified that the compressor was running. Started letting in refrigerant, slowly, low side fluctuated from +50 to +40. No change on the high side. No cooling at all from the vents. When I closed the valve to the refrigerant the low side pressure went back to -20 (vacuum). High side up to 130. 12 oz. can of refrigerant empty.
????
Really, you could have a leak anywhere. If your readings are right, your compressor is working as there is a vac. on the suction line.
Does your system use a TXV (expansion valve) or a cap tube? Have you located these components? Have you checked your evap core for dye indicating a leak? I think earlier you mentioned hearing a psssst upon removing the cover to one or both of your gauge attachment points. If so, they need to be replaced.
Gauges are useful, but they won't help you find a leak.
Does your system use a TXV (expansion valve) or a cap tube? Have you located these components? Have you checked your evap core for dye indicating a leak? I think earlier you mentioned hearing a psssst upon removing the cover to one or both of your gauge attachment points. If so, they need to be replaced.
Gauges are useful, but they won't help you find a leak.
It uses a thermal expansion valve, which is located on the evaporator core which is inaccessible without removing the dashboard...ugh....
The valve could be sticking. Perhaps removing a lower kick panel and a knee bolster will allow you better access?
My evap core has a leak but it's a very small one. I use about 2 cans a year. As long as it leaks no more than this, I'll just keep feeding it refrig.
My evap core has a leak but it's a very small one. I use about 2 cans a year. As long as it leaks no more than this, I'll just keep feeding it refrig.
It suits me to add refrigerant, but it is suspicious that after I added the refrig the temps did not change and the low side started reading vacuum again. Seems to me that if it kept the refrigant in the system that the low side pressure would go up and stay up.
If the TX is stuck how do I "unstick" it? Is that possible without uncharging (discharging??) the system??
If the TX is stuck how do I "unstick" it? Is that possible without uncharging (discharging??) the system??
Well you can tap it (lightly) with a wrench or screwdriver. But you have to be able to access it. That's why I asked earlier. No you don't have to discharge it first.
Haven't read back through the thread so I don't know if your system has dye in it or not. If so, time to look for leaks with a black light.
When I put 134a in my system, it cools off. If yours doesn't, then something else is going on. To better understand how A/C works, I suggest a used textbook from a community college that teaches the subject.
You need to understand how it works before you can diagnose, much less repair.
Haven't read back through the thread so I don't know if your system has dye in it or not. If so, time to look for leaks with a black light.
When I put 134a in my system, it cools off. If yours doesn't, then something else is going on. To better understand how A/C works, I suggest a used textbook from a community college that teaches the subject.
You need to understand how it works before you can diagnose, much less repair.
Originally Posted By: 1 FMF
http://www.aircondition.com/tech/questions/82/
for any r134a system in a car, with engine running and AC on you should see at least 1.5 times the ambient air temp in Fahrenheit over 60F, generally it's around 2x. So for an 80F day you should see over 120psi, generally up around 160-200 psi and the high side will go up and down as the radiator fans kick on and off and heat builds up in the high side of the AC system.
low pressure side is around 30-40 psi. when the ac system engages if the low pressure side goes down below 30 psi then you are most likely low in refrigerant. The low pressure switch generally turns the ac compressor off at 20-25 psi. If the compressor runs for a very short time, shuts off, then turns back on again in 30 seconds then you are most likely low on refig. and the low presure switch is working as it should.
on your honda or toyota they will have a TX valve as opposed to a fixed orifice tube which is common on GM. if you know you have the correct amount of refrigerant in the system and are getting very low side pressures and the system shuts off that can be due to a sticking TX valve. they are around $50.
A common cause for loss of refrigerant is the valves in the high and low side ports where you connect your gauges, try loosing then re-tightening them with a valve tool.
there is no good way checking for correct amount of refrig. in the system since pressure varies with temperature. You can refer to pressure-temperature charts to get you close and that's fine most of the time, but the best way is by evacuating the system and charging by weight. the system is tolerant to usually +/- 2 ounces of r134a. So if it requires 1.5 lbs of r134a, then anything outside of 22-26 ounces becomes a problem. and that +/- 2 oz is a % based on system capacity, for a system requiring less say 1.0 lb then the tolerance is closer to +/- 1 ounce, and vice versa.
here is some more info, see faqs or tech http://www.autoacsystems.com/
+1
Quote:
this is for your 97 toyota avalon correct?
you're either low on refrigerant or have a bad thermostatic expansion valve, known as TEV or TX valve. I believe these are more tolerant to overcharging than an orifice tube system, so you can add an 8 oz can of r134a and see what that does, worst case you get higher compressor head pressure (and lower efficiency) and you'll see that on your high side gauge but the TEV should regulate and give you cold consistent evaporator temps. If one 8 ounce can doesn't help then it's the TEV which is common. If you haven't touched it since the repair there's probably a leak, I would loosen then retighten in the valves in the ports. if they have plastic caps, listen for a little pssst when you undo them if so they are seeping and after a month it will be low and not blow cold.
+2
This is excellent advice.
http://www.aircondition.com/tech/questions/82/
for any r134a system in a car, with engine running and AC on you should see at least 1.5 times the ambient air temp in Fahrenheit over 60F, generally it's around 2x. So for an 80F day you should see over 120psi, generally up around 160-200 psi and the high side will go up and down as the radiator fans kick on and off and heat builds up in the high side of the AC system.
low pressure side is around 30-40 psi. when the ac system engages if the low pressure side goes down below 30 psi then you are most likely low in refrigerant. The low pressure switch generally turns the ac compressor off at 20-25 psi. If the compressor runs for a very short time, shuts off, then turns back on again in 30 seconds then you are most likely low on refig. and the low presure switch is working as it should.
on your honda or toyota they will have a TX valve as opposed to a fixed orifice tube which is common on GM. if you know you have the correct amount of refrigerant in the system and are getting very low side pressures and the system shuts off that can be due to a sticking TX valve. they are around $50.
A common cause for loss of refrigerant is the valves in the high and low side ports where you connect your gauges, try loosing then re-tightening them with a valve tool.
there is no good way checking for correct amount of refrig. in the system since pressure varies with temperature. You can refer to pressure-temperature charts to get you close and that's fine most of the time, but the best way is by evacuating the system and charging by weight. the system is tolerant to usually +/- 2 ounces of r134a. So if it requires 1.5 lbs of r134a, then anything outside of 22-26 ounces becomes a problem. and that +/- 2 oz is a % based on system capacity, for a system requiring less say 1.0 lb then the tolerance is closer to +/- 1 ounce, and vice versa.
here is some more info, see faqs or tech http://www.autoacsystems.com/
+1
Quote:
this is for your 97 toyota avalon correct?
you're either low on refrigerant or have a bad thermostatic expansion valve, known as TEV or TX valve. I believe these are more tolerant to overcharging than an orifice tube system, so you can add an 8 oz can of r134a and see what that does, worst case you get higher compressor head pressure (and lower efficiency) and you'll see that on your high side gauge but the TEV should regulate and give you cold consistent evaporator temps. If one 8 ounce can doesn't help then it's the TEV which is common. If you haven't touched it since the repair there's probably a leak, I would loosen then retighten in the valves in the ports. if they have plastic caps, listen for a little pssst when you undo them if so they are seeping and after a month it will be low and not blow cold.
+2
This is excellent advice.
After several weeks I have found that the AC works more consistently if I put the temp knob to about 75% cold.
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