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A/C not cooling per se

3K views 24 replies 6 participants last post by  Steve83 
#1 ·
Hi all, new to this forum.

05 6.0 Excursion.

Since I bought the Ex in November 15 from Arizona, my AC has never functioned correct.
The rear would get cooler not cold and the front just blows Air (not cool and not hot)

Once it was really hot, front and back so I added a can of Freon and then 2 weeks later happened again. Found a leak on the compressor. Used dye to find leak.

Ordered all new parts.

Changed Compressor w clutch (first compressor was rebuilt so switched out for new one [removing parts twice wasnt fun. My suggestion, always get the new part]), condenser, accumulator, evaporator core (front), orifice tube, all the seals, vacuumed for over an hour and added 4.10 lbs of freon with NO leak stop BS.

The rear would get down to 66 out the vents but the front wouldn't get lower than 78 (basically just fan air). Only when driving and with circulation on.
Even at night, driving at 70 mph, the back would be cold (62) and the front still 78 or fan air.

I ran a system test from AC controls (digital system) to see if I get a code for the Blend door and nothing. Saw the blend door turning during the test.

Checked the lines for leaks and saw nothing.

The condenser was getting extremely hot and the high side pressure, though stable, was well above 250 and low side 45. We put a standing fan in front the condenser and the high side dropped to 190 ish and held it there. So I added an aux 12v fan in front the condenser hoping it would help but the condenser is still extremely hot.
The cold line from the Evaporator (i may be getting this wrong) but the line that supposed to get cold and sweat was warmish and almost hot.

Since the back AC was always cold, I didn't touch any part in the back, only the front.

Where am I going wrong?

I live in Florida so my frustration is high especially with 100 F temperature and my 1 year old daughter in the back seat.

Can anyone help?
:frown2:
 
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#2 · (Edited)
When you did your parts swap, what color was the orifice tube? Was the old one plugged? The rear in the ex has an expansion valve, the front an orifice tube. At 45 psi, the low pressure side should be about 50 degrees F. If it is warmer than that in a dual evap system, you likely have a restriction in that branch. The only other explanations are a massive heat gain in the evaporator overwhelming the carrying capacity of the refrigerant or an expansion valve stuck wide open which could be shunting too much refrigerant through that pathway. I'd expect your low side pressures to be higher and high side lower if that was the case.


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#4 ·
Pressure temperature charts for R134a indicate that at 45 psi, the temperature should be 50 degrees. The temperature of the large tube exiting your front evaporator should be 50 degrees plus any heat absorbed during its pass- that difference between expected and actual is called "superheat ". In a motor vehicle, that's going to be less than 5 degrees. So- if that tube was warm, your problem has to be explained by those findings. Do you have a thermocouple?


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#5 ·
I do not have one, will have to check if the guy working on it does. Well if the tube is warm from the evap, it would be safe to say, there's a problem with the orifice tube. I'll try changing that and see what happens.
I'll also change the expansion valve in the rear and the condenser. I have the thin fin condenser and I'd prefer to go to the tube one.
 
#6 ·
A tube and fin condenser is about 65% as efficient as a parallel flow condenser. If you swap to that style of condenser, you can kiss your a/c system goodbye. R134a requires an efficient heat exchanger to convert the compressed gas into a liquid.

If you change both the orifice tube and the expansion valve, you've covered both logical possibilities for your issue.

It never hurts to clean the evaporators, but this can't be your main issue because if the evaporator was plugged with hair and debris, there would be no heat gain as the refrigerant passed through and the outflow tube would be colder than expected.
 
#8 ·
Where did you get the condenser? Can you take a picture of it? The last tube and fin came out in 1994 on these trucks. That was a serious boo-boo on the parts guy's side.
 
#9 ·
This is a serial-flow condenser:



This is parallel:



This shows the parallel in front of the serial, to compare the tube arrangement:



The right (passenger) end is even-more obvious because there are 2 parallel tubes running along that side, with all the condenser tubes coming out of one & returning to the other.
 
#10 · (Edited)
So it does not get overlooked, check to see if the water shut off valve in the heater supply hose is working. It is located near the engine oil fill tube on the right valve cover and should have a grey vacuum line attached to it. It turns off coolant flow to the heater core with the A/C turned on. Despite the airflow within the HVAC plenum a hot heater core will affect the air conditioning effectiveness.

Don't forget that there is a temperature blend door and actuator...
 
#11 ·
Condenser was ordered from Amazon.
Ordered the Spectre one and should be here today.

Thank you for those images of the condenser. I believe i hsve the correct one now. We'll see when it arrives.

Went outside and checked. 86 out vents (front and back).
Was sweating aftet the evap but hot pass the orifice tube and the pressure which was 45 is now closer to 30.

Would a clogged orifice tube cause a drop in pressure or should I start looking for a new leak?

Im considering changing the rear ac lines.
 

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#12 · (Edited)
A clogged orifice tube would cause an increase in high side pressure and a drop in low side pressure.

It should be hot before the orifice tube - specifically, it should be the temperature equivalent of the pressure (see chart below) minus the heat that was removed going through the condenser. The difference between expected and observed is, by definition, the subcooling. Again, on motor vehicles, not going to be that great. On HVAC units, usually in the 10-13 degree range.

http://www.pacificseabreeze.com/tech-library/heat-and-insulation/R134a-PT-Chart.htm

It would be interesting to see the temperature difference between the section of pipe just past the orifice tube (where you say it is sweating) and the large tube coming out of the evaporator. That heat drop might tell us if there is an excessive heat load on the evaporator core or if your carrying capacity of the refrigerant getting through is so low that it can't keep up.

I still say you are on the right track with your plans to pull the orifice tube and expansion valve.
 
#13 ·
Just to throw a wrench at everyone... while rare and often not really even possible, I have seen orifice tube installed backwards before...
 
#15 ·
...I have seen orifice tube installed backwards before...
The first time I came across that, it blew my mind that some moron could SEE the ears which are molded on to prevent that (and theoretically, to keep it from sliding down the pipe), NOT comprehend what they were, AND be so determined to do things the hard way that he CUT them off just to make it go in wrong.




But other than making it a nightmare to remove, it has no effect on the way a fixed orifice tube works & performs.
 
#14 ·
It continues. Running my truck and noticed hot air coming from front and back. Normally the back would be cooler than the front however it was literally hot air. Check the low pressure side as I only had one of those low side gauges and the pressure was bouncing from 0 to 30 and back to zero. I had lost most if not all freon and it wouldnt engage the compressor. Went to the store, added in one 12oz can of 134a with dye and the system charged up and maintained pressure at 35. It was much cooler inside. Got on the floor and checked with my dye light and glasses for leaks. Traced the entire rear ac line, the system in the back, on the compressor and no leaks. It has to be with this condensee which is the fin type. It must have built up too much pressure causing the compressor to dump the freon. Out of frustration, Im taking it to Ford in the am and they will diagnose the entire system for $110. Hope they can tell me what's going on.
Hot truck + baby(14 months) = no go.
 
#16 ·
No, it doesn't affect the orifice size, but it clogs a whole lot faster!
 
#17 ·
Assuming that's the only error in the installation, it would never clog. Both sides are screened, and it takes a LOT of damage or trash to block up half of the correct one:

 
#18 ·
If they installed that backwards, then it is an awfully large assumption that that would be the only error... honest mistakes happen, but...
 
#19 ·
It's the only way to make this discussion realistic. If we're going to assume that there are MANY errors, then it doesn't matter which way the orifice is installed - any of the other errors would stop the A/C from working long before the orifice stops up.
 
#20 ·
Good point. We should probably get back to the topic anyway.
Any updates on the situation?
 
#21 ·
Ok fellas, update.

Took the vehicle to Ford and they had it for 3 days trying to figure it out. Turns out it was faulty Orificw tube that somehow was forced too far into the line, almost into the dryer line. This caused the system to overheat and compressor dump all the freon. They vacuumed the system, cleaned up previous leak areas and charged it up. Now the system is blowing cold and it has been 2 days since. Hopefully it doesn't have a further leak as this is getting expensive.
Pictures of the broken tube. It was also filty and I'm not sure why because was only in there for 2 to 3 weeks.
Getting 58F out the vents.
 

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#25 ·
Turns out it was faulty Orificw tube that somehow was forced too far into the line, almost into the dryer line. ... It was also filty and I'm not sure why...
That's backward...

The filter collected all that dirt. That caused the refrigerant pressure to go too high (because not enough/ANY was flowing through the orifice). The pressure pushed the orifice past the stop ring crimped into the evaporator inlet, until it bent trying to go around the curve.

The dirt was the root cause of the failure - talk to the person who had the system open previously.
 
#22 ·
Hopefully they flushed it

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#23 ·
Agreed!
We were on the right track with the orifice at least! But something had to of let loose to do that!
 
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