A/C Blows Hot Air - Toyota Nation Forum : Toyota Car and Truck Forums
Avalon 1st Generation (1995-1999) Specific discussion of the first generation Toyota Avalon

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post #1 of 9 Old 04-16-2019, 07:33 PM Thread Starter
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A/C Blows Hot Air

Hello everyone, I have a problem. The a/c in my car is blowing hot air all the time no matter the speed of the blower. The system is fully charged, the compressor is coming on briefly and some lines are cold to the touch while others are warm. I first noticed the problem in the dead of winter because the heat in my car is unbearable whenever I use the defroster. The car has climate control and I still get a little heat if I turn to knob to sixty five degrees. I read online that it is the expansion valve that is bad. I dont want to go and change the valve and it is not the valve, that is why I am putting it to you guys. I do not even know where the expansion valve is located. Does anyone know where it is located incase I have to change it? I am standing by to order my manifold set online to do the repairs myself. I know I have to recover the refridgerant gas from the system, a shop will do that for me. Thanks in advance guy. The colling fans do come on when the a/c button is pressed. 1998 Avalon 245,000 miles.
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Last edited by GoldenGrove; 04-16-2019 at 07:59 PM. Reason: Forget To Mention Car Model
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post #2 of 9 Old 04-16-2019, 08:35 PM
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The expansion valve is attached to the evaporator, which is up under the dash. I think a bit on the passenger side of middle.

It would be best to have high and low pressure measurements before concluding itís the expansion valve. It could be overfilled. Or it could be the compressor is bad.

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post #3 of 9 Old 05-14-2019, 06:53 PM Thread Starter
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BMR, thanks for your input. I did some checking and testing on the system today, I have good news and bad news. I hooked up a manifold guage set to the system and this is what happened. I turned on the a/c on high and it got cold throughout the diferent settings. The low guage was reading not more than 30 PSI and the high side was giving me around 110/120 PSI. Outside temperature was around 52 degrees with the compressor cycling on and off and the fans all working. The sight glass was clouding up everytime the compressor comes on. I Turned it off and it took about 20 minutes for the two guages to give the same reading. I tried it again in the presents of my brother and he said that the a/c is very cold with the two front windows down and doors opened. I left the yard a few minutes after that with the a/c on and it stopped working about a minute later. I started getting hot air although the temperature control knob was on 65 degrees and the a/c light was still on. I forget to rev the engine up to 1500 rpm to see what happens, I will have to do the test again. I have automatic climate control in my car. I personally don't think it is the expansion valve. Why would I get hot air coming up when the temperature switch is set to 65 degrees? The a/c system was never opened since I got the car in 2005 and it was working fine all the time. I don't think it was ever opened by the first owner, I am the second owner. Thanks for any help guys.
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post #4 of 9 Old 05-14-2019, 07:20 PM
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Tis won't exactly be helpful, but... I had an '05 Avalon, and using the A/C, during summer, at various times it would decide, on its own, to put out HOT air to the rear vents. If you shut the A/C off for a few minutes, the problem would go away, and not come back for several hours.



It was diagnosed as some sort of air-mixture ?blend-valve? -part of the automatic A/C temp system- hidden way under the dash. Large price tag to fix, so I just lived with it.
sounds as if your problem may have a similar source.
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post #5 of 9 Old 05-14-2019, 07:40 PM
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Based on what you just said, I think itís simply low on Freon. But get the pressures checked with it idling at 1500 RPM. Thatíll drop the low pressure side a fair bit. Can you override the automatic system? You need to have the fans on high, the temperature control on max cooling, and the idle at 1500 RPM. And it would be best if the outdoor temp was warmer, like above 70įF.

Hereís a good troubleshooting guide from Denso.

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post #6 of 9 Old 05-15-2019, 05:10 PM Thread Starter
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Guys, I just came home from work and doing some trouble shooting at my work place parking lot. Some weird things happened while I was trouble shooting the problem.I am getting slightly cold air when I turned the temperature selector to high and I am getting hot air when I turned it to sixty five. The key to solving the problem is, why am I getting hot air when the temperature selector is on sixty five degrees and the compressor is cycling on an and off? I think a valve behind the dashboard is not doing what it is supposed to do. What goes on behind the dashboard when heat or a/c is selected? what prevents the two of them from coming at the same time? Riick, I think I have the same problem you had on your 05 Avalon, I am not going to live with mine. BMR, I did idle the engine at 1500-2000 RPM earlier today and the reading was, 27 low and 205 high. I started to get cold air at one point and as soon as I gave it gas to go up to 1500 RPM, it started to give hot air and the compressor was on. By the way, I opened the automatic climate control module to see if anything was wrong with it, everything seems ok. I put it on automatic on my way home and was playing with the temperature selector to see if I will get cold air.The blower motor was going from low to high everytime I turned the temperature selector from extreme left to extreme right. That tells me that the temperature selector is working. I have to get this fixed before the summer and I am not going to shell out no big bucks to do it. One more thing, the pressure between the low and the high equalize in about 15 miutes.
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post #7 of 9 Old 05-15-2019, 09:30 PM
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Sounds like the AC systemís charge is good, and the compressor is putting out a decent high pressure. I think everything is good there.

Some vehicles have a blending system in the duct work. Warm air is mixed with cold to provide air to the cabin that is the right temperature. Iím thinking that control system is on the fritz. I have no experience working on those, so I canít offer any further advice, except to say if you canít figure it out, you might take it to an independent shop that specializes in automotive HVAC systems. If they have to tear into the dash to replace a faulty servo motor on a damper door, it might get expensive. But Iím speculating quite a bit there.

2015 RAV4 Limited, AWD, tech pkg, Barcelona red metallic, 62k miles
1996 Avalon XLS, ABS brakes, super white II, acquired w/ 139k, now at 397k
1992 Camry LE, V6 (3VZ-FE), ABS brakes, dark emerald pearl, owned since new. Replaced HGs @332k, totaled at 384k miles
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post #8 of 9 Old 05-16-2019, 12:09 PM
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It was easy for me to live with problem, it was only intermittent. Yours is constant.
You'll figure it out, .... maybe bypass the automation, if possible
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post #9 of 9 Old 05-25-2019, 02:57 PM Thread Starter
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Hello everybody, I found an old post with someone who had the same problem that I am having at the moment. The blend door actuator was acting up in his case. It is the door that opens to give you heat or a/c when either one is desired. The actuator is a real pain to get to, according to the post. I am going to look at mine when I go leave from 31 st of May and will update you guys.
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