Automotive Air Conditioning Information Forum (Archives)
96 Camry A/C loses effectiveness after 20 min...
mytoy on 
Sat July 10, 2010 1:28 PM 
Year: 96
Make: Camry
Model: LE
Engine Size: 2.2
Refrigerant Type: R134
My 96 Camry A/C cools normally for about 20 minutes, then begins to
lose its cooling effectiveness. When cooling ability diminishes I can also
sense a change in humidity, like when it rains.
Here's whats been replaced chasing this:
- New Denso Compressor(not a rebulit one)
-Evaporator
-Condensor
-Expansion Valve
-Filter/Dryer
-Pulled a vacuum on system and recharged
After all these repairs, issue remains. I then took to Toyota dealer and
had them try. They felt the Expansion Valve I already replaced was defective.
They replaced the valve and still not solved. Afterwards they said they found a
clog in the high pressure line and the Dryer which I had already replaced. They
replaced the Dryer and cleared the clogs(so they say). They gave me the car back
yesterday, used the car today and nothings changed. Cooling ability still diminishes
after 20 minutes or so. This car always had amazing A/C before this nightmare began.
I've dumped over $1300 on this....! If this wasn't such a great runniing car I would have
dumped it. I feel trapped, does anyone have a clue as to what could be wrong?
....Desperate.
-------------------------
...Bob
TRB on 
Sat July 10, 2010 2:02 PM 
Pressure readings while it is cooling and when it is not could help diagnose your issues.
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Contact: ACKits.com
94RX-7 on Sat July 10, 2010 7:42 PM
Is the compressor still running when the air gets warm? You may have an electrical issue causing it to cut out rather than an issue with the refrigeration system.
GM Tech on Sat July 10, 2010 8:59 PM
Sounds more to me like evap freeze-up---how is your airflow out the vents when cooling diminishes? open hood when this happens-- is the low sie line frosty white? does it piss like a race horse when you shut system down? all signs of evap freeze-up..
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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
mytoy on Fri July 16, 2010 5:17 PM
-------------------------
...Bob
mytoy on Fri July 16, 2010 5:41 PM
QuoteOriginally posted by: 94RX-7
Is the compressor still running when the air gets warm? You may have an electrical issue causing it to cut out rather than an issue with the refrigeration system.
Thanks for responding...
Yes, the compressor remains running when the effectiveness drops off. I know for certain, I opened
the hood and observed when the system was not cooling. I had my wife press the A/C button to
off and watched the Compressor disengage.
Theres no frosting on any of the lines anywhere. Toyota dealer is totaly stumped. So far they
had me throwing money at part after part. Now they say it might be a clogged high pressure line
and want $1000 to replace the lines. I feel I'm trapped. I've already spent nearly $1500 on this
nightmare. Evetyhing's been replace!
Question....is it possible the heatercore box could be diminshing the effectiveness of the cooling
as the car get hot? The A/C feels perfect for first 20 minutes or so then begins to quickly drop off.
My friend is going to bypass the heater core for me on Tuesday to test the possibilty. I'm doubtful
but who knows.
Also, I see a part labeled "Thermistor" in a parts blowup for the heater/ac assembly. What is its
function?
I really appreciate the expertise of you forum guys, all advice is truly apreciated.
-------------------------
...Bob
Edited: Fri July 16, 2010 at 7:55 PM by mytoy
mytoy on Tue July 20, 2010 12:32 PM
Toyota dealer called me yesterday, they are still baffled with this thing. Can't understand
why it should blow cold for 15 or 20 minutes then lose effectiveness. They assured it was not
freezing up, not low on freon, no leaks and all parts have been replaced except the lines. Now they
say replaceing all lines "may help" but no guarantee. Another $1000....I can't deal with this.
They said the pressures get screwy when the cooling issus occurs. A/C works fine for first 10 minutes.
Really frustrated.....already dumped nearly $1700 in this thing!
HELP!!!!
-------------------------
...Bob
bohica2xo on Tue July 20, 2010 1:29 PM
Parts changers. No talent hacks. And some more colorful terms I will not post here. A kilobuck to replace a perfectly good part? Uh huh.
You replaced the evaporator yourself yes?
That thermistor you are asking about is most likely the source of this issue. It senses the evaporator temperature, and reports this data to the A/C amplifier. The amplifier cycles the clutch off to prevent evaporator icing. There are several ways for this to become a problem, and the monkeys at the dealership should have caught each & every one of them when they replaced the TXV.
1) The thermistor may be failed part. It should be between 4600 and 5100 ohms @ 32f. This is tested with 4 inches of the thermistor in a water & ice mix.
2) The thermistor may have been placed wrong. It should be in contact with the evaporator core itself, down in the fins.
3) The thermistor may have be disconnected. It HAD to be disconnected to remove the evaporator box.
4) The thermistor may have been discarded with the old evaporator, and not replaced.
The monkeys should have checked the thermistor. A quick look with a DMM can save a second evaporator R&R
The monkeys should have SEEN a misplaced thermistor, and corrected it with the evaporator case on the bench.
The monkeys should have re-connected anything you missed connecting when they put the case back in.
The monkeys should have noticed this missing, essential part.
If the system cools normally, then drops off - with the compressor still turning... it is most likely icing the evaporator core.
B.
-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
mytoy on Tue July 20, 2010 3:09 PM
QuoteOriginally posted by: bohica2xo
Parts changers. No talent hacks. And some more colorful terms I will not post here. A kilobuck to replace a perfectly good part? Uh huh.
You replaced the evaporator yourself yes?
That thermistor you are asking about is most likely the source of this issue. It senses the evaporator temperature, and reports this data to the A/C amplifier. The amplifier cycles the clutch off to prevent evaporator icing. There are several ways for this to become a problem, and the monkeys at the dealership should have caught each & every one of them when they replaced the TXV.
1) The thermistor may be failed part. It should be between 4600 and 5100 ohms @ 32f. This is tested with 4 inches of the thermistor in a water & ice mix.
2) The thermistor may have been placed wrong. It should be in contact with the evaporator core itself, down in the fins.
3) The thermistor may have be disconnected. It HAD to be disconnected to remove the evaporator box.
4) The thermistor may have been discarded with the old evaporator, and not replaced.
The monkeys should have checked the thermistor. A quick look with a DMM can save a second evaporator R&R
The monkeys should have SEEN a misplaced thermistor, and corrected it with the evaporator case on the bench.
The monkeys should have re-connected anything you missed connecting when they put the case back in.
The monkeys should have noticed this missing, essential part.
If the system cools normally, then drops off - with the compressor still turning... it is most likely icing the evaporator core.
B.
Thank you so much for the guidance!!!!
Answer to your question re evaporator being replaced. Yes, it was replaced, not by me personally, was
replaced at same time the shop that replaced all the other stuff. Comp, Evaporator, Condensor, Dryer,
Exp/Valve. That shop gave up, said they had no more ideas on what was wrong. Cost about $1300.
Then brought to Toyota, they changed the Exp/Valve AGAIN and the Dryer AGAIN. Paid Toyota another
$500. Said they found two blockages that they felt were the problem. Still no change...thats when they
said maybe change the lines.
I asked ServMgr the question, whts a Thermistor? He said was only relevant to car with Auto Climate Control.
Is this true????
-------------------------
...Bob
Edited: Tue July 20, 2010 at 3:11 PM by mytoy
bohica2xo on Tue July 20, 2010 8:59 PM
Then the service "manager" is king of the monkeys.
Your Toyo is more than 10 years old. They have no interest in fixing it, but I bet they could offer you a nice trade in on it...
Perhaps you can find an independent shop that is an A/C or toyota specialist? Tell them your tale, and ask if they can check / replace the thermistor? Or another dealer in a nearby town?
B.
-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
mytoy on Wed July 21, 2010 4:19 PM
QuoteOriginally posted by: bohica2xo
Then the service "manager" is king of the monkeys.
Your Toyo is more than 10 years old. They have no interest in fixing it, but I bet they could offer you a nice trade in on it...
Perhaps you can find an independent shop that is an A/C or toyota specialist? Tell them your tale, and ask if they can check / replace the thermistor? Or another dealer in a nearby town?
B.
-------------------------
...Bob
mytoy on Wed July 21, 2010 4:41 PM
QuoteOriginally posted by: mytoy
Quote
Originally posted by: bohica2xo
Then the service "manager" is king of the monkeys.
Your Toyo is more than 10 years old. They have no interest in fixing it, but I bet they could offer you a nice trade in on it...
Perhaps you can find an independent shop that is an A/C or toyota specialist? Tell them your tale, and ask if they can check / replace the thermistor? Or another dealer in a nearby town?
I agree, I'm sure the Toyota dealer would be delighted if I just gave up and purchased a new car.
Truth is if this car wasn't so well maintained by me, runs so great and looks pristine I would consider
selling or trade-in. But...Its too good a car. Maybe I'm being stupid about this.
Talked with service manager this am, he's still at a loss. I again asked about the Thermistor. He still
claims they feel a blockage in the lines. He said when they were replacing the Exp/Valve and Dryer while
system was open they tried blowing the lines. Said one of the lines(rubber hose) at first would'nt allow
air to blow through. Said they heard a "pop" and then air blew theough freely. Felt that was the problem.
However, we know it wasn't the problem cause isuue remains. Basd on this account, he feels possible more
clogs??? But no guarantee!
I again asked about the thermistor, he said he would meet with his guys. I also asked about replacing the
hose he said he heard the "pop" when blowing out. I'm waithng to hear back from him.
Don't know if I mentioned, Compressor doesn't seem to cycle, stays engaged all the time as far as I can
observe.
Do you still feel the Thermistor is a prime culprit here? I will insist on getting it changed if your experience
leads us there.
BTW, your User ID says it all...BOHICA! Thats exactly whats happening to me with this disaster! haha
Thanks very much for hanging in with me on this....
...Bob
-------------------------
...Bob
Edited: Wed July 21, 2010 at 5:18 PM by mytoy
Bench on Wed July 21, 2010 5:44 PM
Bob, Where are located? If your close I would be willing to help. I just like working on vehicles, and wouldn't charge you a dime. I am in Shreveport ,LA.
Edited: Wed July 21, 2010 at 5:46 PM by Bench
mytoy on Wed July 21, 2010 6:00 PM
QuoteOriginally posted by: Bench
Bob, Where are located? If your close I would be willing to help. I just like working on vehicles, and wouldn't charge you a dime. I am in Shreveport ,LA.
Thank you for the generous offer, you're a true gentleman. Unfortunately(for me) I'm
not near you. I live in Paramus NJ, is Northern NJ. I'd almost travel to Shreveport but
without fully funcional A/C woud make it a Loooooog trip. haha
Thanks very much!
-------------------------
...Bob
bigkev on Thu July 22, 2010 4:32 AM
overflow tube ok?
mytoy on Thu July 22, 2010 9:06 AM
QuoteOriginally posted by: bigkev
overflow tube ok?
-------------------------
...Bob
mytoy on Thu July 22, 2010 9:09 AM
QuoteOriginally posted by: mytoy
Quote
Originally posted by: bigkev
overflow tube ok?
Yes, not blocked.
-------------------------
...Bob
bohica2xo on Thu July 22, 2010 11:40 AM
I wish I could use stronger terms... screaming, intellectually challenged, aids infected, feces eating monkey parts changers.
A RUBBER HOSE you could not blow through? and they put it back on a customer's car?
IF they are telling you the truth, that hose should never have been put back on the vehicle. On rare occasions, rubber hoses fail internally. The inner liner becomes detached, and blocks flow. Or otherwise creates odd flow behaviour.
If you remove a hose that should flow freely and it does not, most mechanics would blow compressed air into it to see what was in it. The system is sealed. There is no way for odd things to get in there from outside. Once the line cleared, and nothing came out - every mechanic I know would have replaced the line. (and cut it open to see what the *%#@ that was)
I asked before - does the airflow from the vents slow down when the cooling deteriorates? The discharge air will be cold, but there will be less of it. Is this what is happening?
The insistence that the thermistor is not part of your car makes me doubt their honesty - or knowledge. The "clog" story smells too. A clogged high side will cause a high pressure event. Either a cycling on the high pressure cutout, or a popped relief valve.
You would be ahead of the game to buy / rent / borrow a set of gauges. It would really help to know the pressures when this system is running.
B.
-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
mytoy on Thu July 22, 2010 4:31 PM
QuoteOriginally posted by: bohica2xo
I wish I could use stronger terms... screaming, intellectually challenged, aids infected, feces eating monkey parts changers.
A RUBBER HOSE you could not blow through? and they put it back on a customer's car?
IF they are telling you the truth, that hose should never have been put back on the vehicle. On rare occasions, rubber hoses fail internally. The inner liner becomes detached, and blocks flow. Or otherwise creates odd flow behaviour.
If you remove a hose that should flow freely and it does not, most mechanics would blow compressed air into it to see what was in it. The system is sealed. There is no way for odd things to get in there from outside. Once the line cleared, and nothing came out - every mechanic I know would have replaced the line. (and cut it open to see what the *%#@ that was)
I asked before - does the airflow from the vents slow down when the cooling deteriorates? The discharge air will be cold, but there will be less of it. Is this what is happening?
The insistence that the thermistor is not part of your car makes me doubt their honesty - or knowledge. The "clog" story smells too. A clogged high side will cause a high pressure event. Either a cycling on the high pressure cutout, or a popped relief valve.
You would be ahead of the game to buy / rent / borrow a set of gauges. It would really help to know the pressures when this system is running.
B.
Answer to the airflow question...Airflow doesn't feel any different other than the coolness when the
a/c looses its cooling effectiveness. I wish I could say there was noticable difference in air flow so
we'd have a deffinate system to chase down. Its always about the same other than fact I crank up
the fan speed to max just so as to get as much cooling as I can. When system is working normally,
after car gets to comfortable I generally have fan speed on second speed. Even on highest speed
level, the cooling is less than marginal but airflow is intense.
I'm picking up the Thermistor part from the dealer in a few minutes but will not have them do the work
for reasons you infer. Will let you know if the Thermistor resolves anything.
Also trying to find out from Toyota which line they claim "poped" when blowing air through. they have
yet to call me back. Nice hah?
Many thanks for continued interest and advice....greatly appreciated!
-------------------------
...Bob
Edited: Thu July 22, 2010 at 5:46 PM by mytoy
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