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  #1  
Old July 27th, 2016, 09:40 AM
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Evaporator freezing on long trips

Does anyone else have this issue? The system is fully charged and this seems to only happen on trips longer than 1 hour. I am missing the cover for the evaporator pipes, so I can see when it is freezing. I recently did a 20 min vacuum on the system before recharging it. This was really bad over the weekend driving from Va to NYC when it was 95+F outside. I had a very unhappy fiancée and Husky.
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  #2  
Old July 27th, 2016, 09:56 AM
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I had the same issue with my kool air under dash ac several years ago, along with an F'd up harness. I had to learn all about AC myself and resolve the issue myself as well. We're dealing with AC's designed in the breezy UK, not subject clearly to the humidity and heat combo we see here.

here's what i figured out. The AC has a temp prob that is fitted around the point where the evaporator side (passenger portion) meets the skinny middle union. If you unscrew your side and middle mounting screws and let your ac drop down a bit to view the top, you'll probably see the probe. THAT PROBE POSITION SUCKS! in hot, hot weather, the air warms up too much between the evaporator and the probe. That probe's sole function is to prevent the evaporator from freezing by telling the ECU to shut off the compressor when the air coming off the evaporator is cold enough.

my fix was to relocate the probe closer to the evaporator (maybe 6") so that the probe gets a truer reading on the actual evaporator temp, allowing the ECU to prevent evaporator freezup by shutting off the compressor in time.
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  #3  
Old July 27th, 2016, 10:08 AM
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IME the 97's system does not perform well in high temp, plus high humidity. I can't imagine one put to the task of cooling the volume of air in a 110 on a humid day.
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  #4  
Old July 27th, 2016, 10:30 AM
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mark kellgren
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Quote:
Originally Posted by 1of40 View Post
IME the 97's system does not perform well in high temp, plus high humidity. I can't imagine one put to the task of cooling the volume of air in a 110 on a humid day.
actually, with window tinting plus proper cabin insulation and the probe change on my AC, mine stays nice and cool in 100F heat. mechanic at safari even commented on how nice and cool my cabin stayed in FL.
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  #5  
Old July 27th, 2016, 11:20 AM
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Quote:
Originally Posted by Overlander View Post
I had the same issue with my kool air under dash ac several years ago, along with an F'd up harness. I had to learn all about AC myself and resolve the issue myself as well. We're dealing with AC's designed in the breezy UK, not subject clearly to the humidity and heat combo we see here.

here's what i figured out. The AC has a temp prob that is fitted around the point where the evaporator side (passenger portion) meets the skinny middle union. If you unscrew your side and middle mounting screws and let your ac drop down a bit to view the top, you'll probably see the probe. THAT PROBE POSITION SUCKS! in hot, hot weather, the air warms up too much between the evaporator and the probe. That probe's sole function is to prevent the evaporator from freezing by telling the ECU to shut off the compressor when the air coming off the evaporator is cold enough.

my fix was to relocate the probe closer to the evaporator (maybe 6") so that the probe gets a truer reading on the actual evaporator temp, allowing the ECU to prevent evaporator freezup by shutting off the compressor in time.

That's good info, although I would guess that mine utilizes an orifice tube and is not electronically controlled. Maybe someone can chime in a little more on the operation of the factory system since I don't know much about it.

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Originally Posted by 1of40 View Post
IME the 97's system does not perform well in high temp, plus high humidity. I can't imagine one put to the task of cooling the volume of air in a 110 on a humid day.
Don't you run without a condenser fan?
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  #6  
Old July 27th, 2016, 11:39 AM
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Originally Posted by Jymmiejamz View Post
That's good info, although I would guess that mine utilizes an orifice tube and is not electronically controlled. Maybe someone can chime in a little more on the operation of the factory system since I don't know much about it. Don't you run without a condenser fan?
True, no condenser fan.
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Old July 27th, 2016, 12:22 PM
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Doesn't a freezing line indicate low Freon? Could be you may have a faulty pressure switch or the compressor isn't up to the task? Did you happen to have a temperature gauge with you? In a house the temperature difference between the return air and a vent should be around 14-20 degrees with the outside temp above 80. In the Defender the return air is the temp in the cabin.
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Old July 27th, 2016, 12:50 PM
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Jimmy:
R143A runs at a lower pressure that R12.
So if you charged using old R12 gauges and standards, your system is overcharged and this will cause evaporator freezing.
When I setup the Diavia controls in the 110, actually put the probe in the less cooler side of the evaporator fins.
The unit produces really cold air and does not freeze.
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  #9  
Old July 27th, 2016, 02:05 PM
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Quote:
Originally Posted by Capt Milks View Post
Doesn't a freezing line indicate low Freon? Could be you may have a faulty pressure switch or the compressor isn't up to the task? Did you happen to have a temperature gauge with you? In a house the temperature difference between the return air and a vent should be around 14-20 degrees with the outside temp above 80. In the Defender the return air is the temp in the cabin.

In cars, newer Land Rovers at least, the temp coming out of the vents is usually 35-40F. My a/c blows very cold, so I would expect it to be around that temp.

Quote:
Originally Posted by rdavisinva View Post
Jimmy:
R143A runs at a lower pressure that R12.
So if you charged using old R12 gauges and standards, your system is overcharged and this will cause evaporator freezing.
When I setup the Diavia controls in the 110, actually put the probe in the less cooler side of the evaporator fins.
The unit produces really cold air and does not freeze.

My truck has R134A fittings on the lines from the factory, so it isn't converted from R12 as far as I know. I thought only undercharging causes freezing?


I should probably pull this apart and look at the location of the probe.
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  #10  
Old July 27th, 2016, 02:24 PM
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Quote:
Originally Posted by Jymmiejamz View Post
My truck has R134A fittings on the lines from the factory, so it isn't converted from R12 as far as I know. I thought only undercharging causes freezing?
To my knowledge all the D90s used R134A.
Wasn't talking about converting from R12.
Was talking about if you charged your system with R12 gauges adapted for R134A. and charged them to R12 standards (like I did back when R134A had just come out), then your system could be running with a higher pressure than it needs.
R134A operates about 50 pounds lower than R12.

Being overcharged can cause freezing with R134A as well, but you're right having low pressure in itself can cause freezing.
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  #11  
Old July 27th, 2016, 02:49 PM
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Quote:
Originally Posted by rdavisinva View Post
To my knowledge all the D90s used R134A.
Wasn't talking about converting from R12.
Was talking about if you charged your system with R12 gauges adapted for R134A. and charged them to R12 standards (like I did back when R134A had just come out), then your system could be running with a higher pressure than it needs.
R134A operates about 50 pounds lower than R12.

Being overcharged can cause freezing with R134A as well, but you're right having low pressure in itself can cause freezing.


Okay, I misunderstood you. I used an R134a machine to charge the system. It doesn't even have the capability to do R12.


Can anyone tell me what the correct amount of refrigerant is for what I believe is a Wynnes system? As a side note, I am doing this on the 5th floor of our building and we have had a/c charging issues due to the building swaying. sometimes we have to go to the first floor of the building when dealing with R1234-YF because the machine is so sensitive.
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