variable orifice tube ?

jericho

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I'm the opposite, I fill to the spec, maybe a little more. We actually do have a spring here in ohio that will be 70 degree temps and extremely humid. We use ac for water removal as much as we do for air cooling. I would for sure have an evaporator freeze up if I undercharged.

Typically, on retrofits, I look for low side pressure to be around 40 idling in the shade, max ac selected. But I also install either a high pressure compressor cut off, and/or a pusher fan, so extreme high side temps don't concern me.

The pusher fan is mainly for idle cooling. On some vehicles I've had issues with it even after messing with orifice tube sizes. I think on some vehicles a viscous fan clutch simply doesn't sense condenser heat. Electric Pusher fans can be had for dirt cheap, and they solve the problem.



This is the biggest thing. You gotta do what works for you, and each truck/climate is different.

I didn't realize low charge could cause freeze up. I also use my ac a lot of the time for high humidity and moderate temps. Also almost any time its raining my windows fog up in my reg. cab and the ac defrost saves the day. I will keep this in mind.
 

franklin2

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Never seen low charge cause a freeze up on a automotive system. I have seen it on residential systems.

Ford uses the low pressure switch to control cooling on the systems in these trucks. Low charge just causes more clutch cycling and poor performance. I have found there is a wide window of charge amount where it will work though.
 

Black dawg

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I have had the evaporator freeze up on my truck a couple times, both times system was charged to spec.

Both times was during 32-33 degree HEAVY snow, running the defrost with a fully heatsoaked truck. Pretty weird when the airflow coming out of the vents slows down to nothing and you can still hear the fan blowing. THe one time it took almost 10 minutes for it to melt enough to get air flow back. I have had it start to happen since then, Now I just stop and pull the low pressure switch connector.
 

jericho

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Well I finally got around to the AC repair after all this time because of busy stuff stopping any work on it during most of August, but thanks to all the very helpful advice it's up and running pretty good! A few interesting notes though.
The old orifice tube ( all parts were original) was clogged with the grit of death.
When removing the receiver/dryer and compressor, not one drop of oil came out! Blowing air through every other part brought no
noticeable oil out either. The compressor was greasy oily on the bottom so it probably very slowly leaked it all out. I found no leaks
after reassembly with just these three new parts: orifice tube , rec/dryer, and compressor. (o-rings)
The orifice tube was a bear to to get out. I heated it up like I read one comment, but too much. It melted and just got the top to pull out. finally while heating it I blew air through the other end of the evaporator and POP! the bottom came out. But melted blue plastic was a pain to try and clean out.
Flushed all the parts out, but I admit I didn't clean the outside of the condenser or evaporator knowing the evap must be filthy.
I used ester oil just to be safe if my flushing wasn't thorough enough to get rid of all the old r12 mineral oil.
I initially put in 8 oz of oil but I screwed up with one connection before vacuuming some into my vacuum pump!cookoo
soooo I added more oil to the system to be safe. Not sure if I'm over 1 or 2oz on the oil.
38 oz of r134a. orange orifice tube.
The result is 50F at the vent driving, ambient temp about 80F. I know it could be better. It could be too much oil, or a very dirty
evaporator,( or something else) but this being a standard cab it cools pretty easily, and feels good! The last time I checked the gauge numbers they looked pretty normal I think: 45 low 225 hi ? I've got to check them again though. Anyone have any opinions they will be appreciated.
 

chris142

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Well I finally got around to the AC repair after all this time because of busy stuff stopping any work on it during most of August, but thanks to all the very helpful advice it's up and running pretty good! A few interesting notes though.
The old orifice tube ( all parts were original) was clogged with the grit of death.
When removing the receiver/dryer and compressor, not one drop of oil came out! Blowing air through every other part brought no
noticeable oil out either. The compressor was greasy oily on the bottom so it probably very slowly leaked it all out. I found no leaks
after reassembly with just these three new parts: orifice tube , rec/dryer, and compressor. (o-rings)
The orifice tube was a bear to to get out. I heated it up like I read one comment, but too much. It melted and just got the top to pull out. finally while heating it I blew air through the other end of the evaporator and POP! the bottom came out. But melted blue plastic was a pain to try and clean out.
Flushed all the parts out, but I admit I didn't clean the outside of the condenser or evaporator knowing the evap must be filthy.
I used ester oil just to be safe if my flushing wasn't thorough enough to get rid of all the old r12 mineral oil.
I initially put in 8 oz of oil but I screwed up with one connection before vacuuming some into my vacuum pump!cookoo
soooo I added more oil to the system to be safe. Not sure if I'm over 1 or 2oz on the oil.
38 oz of r134a. orange orifice tube.
The result is 50F at the vent driving, ambient temp about 80F. I know it could be better. It could be too much oil, or a very dirty
evaporator,( or something else) but this being a standard cab it cools pretty easily, and feels good! The last time I checked the gauge numbers they looked pretty normal I think: 45 low 225 hi ? I've got to check them again though. Anyone have any opinions they will be appreciated.
pressures are too high for 80F. Overcharge? Fan clutch?
 

jericho

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This was my first chance to check my gauge numbers after your post chris142. My last numbers I think was while I was still filling up.
right now is:

cycling low side 25-45 psi
cycling hi side 95-155 psi
ambient temp 72F
temp at vent 55F

I hope this is more normal, obviously I wasn't reading the gauges correctly before. And my fan clutch seems to work ok.
 
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chris142

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Also. You need to adjust the low pressure cycling switch to shut the compressor off @20 instead of 25
 

riphip

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Cold and sweating Sounds Good!! At least you are at a point where you have cooling & can watch it. Ideal rpm to check pressures is 1500-2k. Warm weather will be back soon to check your charge. :Thumbs Up
 

jericho

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I adjusted the low pressure cycling switch to cut off at 20F. now temp at the vent is 50F. Ambient temp is 75F. And the suction line is cold all the way to the compressor. This is within 5 minutes of starting the engine, regular cool and low fan, doors shut.
 

jericho

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I'm hoping this is closer to normal pressures and temp. Gonna try what I read on another thread. They said remove the blower and spray evaporator cleaner inside then check the condensate drain is clear. I guess then rinse it real good.
 

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