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Intermediate A/C trouble in 95 Toyota Avalon


UncleD's Avatar
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08-15-04, 04:50 PM   #1  
UncleD
Intermediate A/C trouble in 95 Toyota Avalon

My 95 Toyota Avalon has developed a part time A/C problem. The A/C works as normal most of the time, but every once in a while, when driving for an extended period time (>30 minutes) the cooling seems gradually fall off. The blower continues to move air as normal, just warmer & warmer. This happened about 40 minutes into a daytrip (2.5 hr. drive) and I stopped to see if the suction line is frosted up anywhere, but all appeared normal (sweating of suction line and a very warm discharge with compressor clutch engaged and no abnormal noises). After the car was off for a 4 hr. period the unit was back to cooling normally for the entire return trip home. There's no sight glass in this system to indicate state of charge. Could this be in my air ducting/dampeners or is there something I'm not looking at?
Thanks, Doug

 
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08-16-04, 05:07 AM   #2  
It could be a freezing problem in the evaporator. You have a thermostat designed to prevent that but it may have a problem. I would get a digital thermometer and drive around with it in the center vent for a while and monitor the temps there. If that temp starts to drop below 40deg, the t-stat should be cycling the compressor off until it warms up. If not it will eventually freeze. You say the fan keeps on working. Does it seem to reduce the actual volume of air coming out of the vents when this happens? Don't judge by sound, feel the air flow.

 
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08-16-04, 03:03 PM   #3  
Does it happen when you have the blower on the lowest setting while you have the temp to the coolest setting?

 
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08-16-04, 06:52 PM   #4  
UncleD
Desi501 - Excellent point, I have not monitored the output temp but I will be for the next few days just to see how far the air temp will drop. The volume of air movement doesn't seem to change, and at the times I've noticed the air warming, I've switched the fan to a higher speed and I can feel the airflow is not restricted. Thisis part of the reason why I question the air ducting & dampeners and if a fresh air damper could become open allowing warm air in to system or if it may be possible for the cold air (after the evaporator) to find a path out of the car.

toyotaman11769 - You guessed it, habit here has always been to control the interior cooling by air speed and not by air temp. Seem's to be the pattern I've developed that has followed me and my vehicles. Now this pattern doesn't apply during heating season, but for cooling, the only reason I 'd move my t-stat from 55 would be because I've found a 45 . And true enough, once the A/C achieves a better than comfortably cool, that's the mark to reduce the blower speed.

Thank you both for your interest and I will be posting my air temp findings in the coming days.
Doug

 
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08-17-04, 03:06 AM   #5  
Your freezing the evaporator, control the temp by mixing heat in.

 
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