As most of my business revolves around older system before the advent of variable volume compressors I am only guessing here.

Looking at the info It would be my opinion that it is the control valve. The low side is high other than in a small RPM area. The high is low other than in the same area. This would lead me to believe the compressor is not "recovering" the total refrigerant vapor that the expansion valve is allowing into the evap.

Anybody else??

What is your static pressure with the system off and with the 100* ambient temperature.

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The static press. at 100* amb. is 115 psi. both sides. This is with the engine at ambient also.

With the engine running and AC off the low side will go to 350 psi. after a few minutes. Thats as high as my low side gauge will go. BUT... any measurement over 120 on my low side gauge is guess work. The low side connection is low on the left side, near the firewall in a very warm spot, and difficult to access.

The car is 5 years old, was bought new and the AC is currently as delivered from the factory. No work done prior to now, never had a problem before now. Mileage is 100K.

Thanks for the tip about Mitchell. I have a lift so thats not an issue. I have been rebuilding old cars for about 20 years as a hobby, just never messed with AC before now.

Yes, it has rear AC, do you know if the TXV for the rear is on the firewall with the front TXV? Its not that easy to see with the cross brace in place.

"That low side should be a flat line about 33 psi. " Is the flat line of 33 psi at a 100* ambient?

I had the refrigerant recovered, there was 18 oz in the system.
Could find no indication of a leak. Tech also took a quick look around and saw no sign of a leak.
I then added another 20 oz to reach 38 oz. as noted on the tag under the hood.

Air at vent is still warm except at elevated RPM (2000-3000)

ambient temp was 98*
relative humidity 36%

RPM-----------low side------------high side

750-------------88-------------------190
1500-----------84-------------------240
2000-----------75-------------------285
3000-----------63-------------------370

Looks like I need some parts?

Edited: Wed August 04, 2010 at 9:11 PM by philso

ambient temp was 94*
relative humidity 42%

Ran vehicle for about 10 minutes and took the following readings. NO water on condenser.

RPM-----------low side------------high side

750------------81-------------------165
1500-----------71-------------------205
2000-----------66-------------------280
3000-----------55-------------------350

sprayed water over the condenser for about 10 minutes. Pressure slowly dropped from 81 to 72 psi on low side and slowly from 165 to 110 on the high side (@ idle). Sprayed water for another 10 minutes, low side press. stayed at 72, high side press stayed at 110.

Took the following readings.

RPM-----------low side------------high side

750------------72-------------------110
1500-----------65-------------------115
2000-----------60-------------------125
3000-----------49-------------------130

The fans have always been running, both of them with a good amount of air flow. I have checked them several times, but not at the higher speeds/ higher pressure. I will do that. The fans could be howling, but then so is the engine.

It will take a couple of days to get the control valve, will post new pressures asap.

I have removed the center plastic cover from in front of the car, what one might laughingly call the grill, for better visibility and accessibility to the condenser. As far as the cleanliness of the condenser, I can see shiny tubes from both sides of the condenser through the cooling fins. Some of the fins at the bottom of the condenser are bent over from bug impacts. This affects the bottom 20% of the fins. This lower 20% may be 25% blocked from bent cooling fins. The upper 80% of the condenser looks straight as new. This would net to a 5% total impact on the condenser fins.

By scan tool, I assume your asking about the codes that are accessible from the connector under the steering wheel. No, I don't have a scan tool but will work on getting the codes.
Will most of the tools sold recover the AC codes if they are present? Or, would I need one with specific capability?

Making progress but still not fixed.
The high pressure problem seems to be still with me.
I changed the control valve in the compressor and the system is blowing cool/cold air at all speeds both front and rear systems.

Ambient Temp: 82*
Engine Temp: 185*
Static press: 92 psi - both high and low- taken prior to starting vehicle, engine cold.

RPM Low High
700 50 250
1500 42 310
2000 38 350
3000 32 pressure climbs steadily to about 420 psi, and system shuts down.

AC pressure relief valve "close pressure" is spec'ed at 450 psi.


with water running over the condenser...
RPM Low High
700 51 175
1500 42 200
2000 35 225
3000 32 280

There are no DTCs posted or pending.
I do not detect a change in fan speed at any RPM/Pressure.

With the AC off the fan cycles ON at an engine temp of about 210*F and cycles OFF at about 200* F.
The thermostat (by spec) begins opening at 183* F, and is fully open at 203* F.

With the AC on the fan runs continuously.

Did you get this system working any better?
The info you have now leads me to believe you have one of two or three problems, possibly all. The high side pressures at 82 ambient are higher than I would have expected. With water over the condenser (guessing your water to be at about 68*) the high side should be considerably lower than the numbers you have posted.

1. The condenser is partially plugged. Even with water over the surface the high side pressures are a bit higher than what I would have expected. What are the inlet and outlet temps?
2. The compressor is "bad". The high side pressures could be caused by a compressor with an internal "leak". This would cause it to "recompress" the vapor which in turn will drive the high side temps and pressures up.
3. System is charged slightly wrong. The little I know about the variable systems has been gleaned from this site and studying the theory of operation on them the past couple of weeks. So if I am understanding properly the charge level is quite critical on these newer system in order for the control valve to operate properly.

Mind you I am not discounting the possibility that the fans are not keeping up with the demand. Just saying with water flowing over the condenser the fans are not nearly as important. The water will do the cooling even if the fans are off. I would think you need to find the problem with the high side pressures/temps before you continue. As this can be caused by a number of things I am not sure where I would advise you start first. Personally I would not spend any more money until you have a good idea where the problem is.

Philso:

The first line of your first post "My Freestyle blows warm/cool air at idle works OK at highway speed." - is a classic description of a condensor airflow problem.

In addition to that issue, you also had a failed control valve, and were 20 ounces low on refrigerant. As I predicted, once you solved the valve problem & charged fully - your high side pressures got ugly.

There is nothing wrong with your compressor - it manages to push 400+ psi. The performance is typical of a scroll with a few miles on it, performance is directly related to compressor speed. If you were to set the cabin fans to the lowest speed, you would see the control valve pick things up at a lower rpm.

After looking at the diagnostic chart again, I will say that the pressure transducer is probably OK, based on the compressor shutdown @ 400 psi.

Sure, the condensor could have some blockage - but from what? The compressor is original, and scroll compressors that shed enough material to block condensors usually do so on the last 10 revolutions they ever make.

If you have long enough gauge lines, duct tape the gauges to the windshield & go for a drive. If the 60 mph air blast is enough to keep the pressure down to reasonable levels, it can only be the fans.

That vehicle has a lot of glass, and two evaporators. It never had really low condensor pressures, but it should have enough fan to keep it from dropping the compressor on a 115f day.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

I invested in some additional software for my scan tool and now know the AC pressure transducer is working fine.
The OBD monitored pressure runs consistently about 20 PSI higher than the gauge pressure. The sensor is located at the compressor, the gauge port is a couple of tubing feet away.
I agree that with the system shutting down due to high pressure it was a strong indicator, but I was not ready to accept a single data point as confirmation. With the new software I am able to monitor the Ford enhanced PIDs, one of which is the AC Pressure sensor.

I also now know the Engine Temp. (which we already knew) sensor is working well and the Evaporator Temp. Sensor is working well.
These are the inputs to the PCM that drive the fan duty cycle from the PCM to the FCM.

I also measured the volts to the fan at the fan connector between the FCM and the fan itself, this with a meter. While at idle with the AC on this typically runs 8 to 9 volts, it does ramp up to Vbat when the RPM and the AC Pressure increases. With the AC off the fans only run briefly at 8 to 9 volts to drop the coolant temp. below 200*

I did mislead when I said previously the fans do not change speed, I looked more closely after measuring the voltage and they do change speed but in my judgement the speed change is very small. I don't have a strobe so am relying on airflow change that I can hear and feel.

With regard to the fans I am monitoring...
FANDC_____Variable Speed Fan Duty Cycle..........%_________7.5 to 86% (full range)
FANVAR ___Variable Speed Fan Level...................%_________0 to 100% (full range)
FANVARF___Variable Speed Fan Output Fault....YES/NO______This always shows "No Fault"
FANSSM____Fan Speed Sensor Monitor............LOW/HIGH____This always shows "LOW"

Mitchell does not give much information on these PIDs but I think the FANDC is the output from the PCM going to the FCM.
I am not sure what FANVAR is measuring but it tracks FANDC fairly well but consistently shows a lower % reading up to about 65%, they track together from 65 to 75%, then FANDC tops out at 86% and FANVAR continues rapidly to 100% before topping out.

Driveway measurements....
PID______________750______1450________2000________3000
FANDC_%__________64_______82__________83__________86
FANVAR_%_________67_______100_________100_________100
AC Press(OBD)_psi__286_______335_________352_________436 (compressor shut down)

The low side tracked to the values given previously (gauge readings).
_psi_____________52________44__________36__________32

Driving Measurement.........
I monitored the AC Press with the OBD meter.
Driving for a couple of miles stretch on the highway at 60 to 63 MPH
RPM varied a little but typically was at 2000. This vehicle has a CVT and RPM is not always under direct driver control.
AC Press was 230 psi.
FANDC was 7.5%
FANVAR was 0% Net. there was no fan running at this speed.
The evaporator air temp. was 43*F to 45*F.
I did not monitor low side press.

As I slowed down the fans ramped up.

I am monitoring the available AC fault PIDs. All show NO FAULT. There are no fault codes Stored, Permanent or Pending.

It appears more air over the condenser would definitely fix the high side pressure problem. As you have said for a while, this is likely the problem. I think the next step is to replace the fans. Not a cheap undertaking in this vehicle. I wish I understood a little better exactly what the PIDs were measuring. But I seriously don't want to have to replace the PCM. Even with the pictures in Mitchell, I have not been able to find the PCM.

Philso:

Excellent work. All that OBD stuff does come in handy sometimes.

It looks like everything is working well enough at highway speeds. Fasto has a valid point, if you are missing an air dam it could be recirculating a bit with zero vehicle speed.

The only thing that jumps out at me is the "FANSSM" always showing "Low". The fan controller & PCM seem to be doing their jobs, but the fan speed feedback is not seeing a large enough speed increase to show a change. The fan motors themselves could be tired, worn brushes / bearings etc.

Unfortunately the factory does not provide an RPM range to check fans against. If you happen to have a photocell tach (or can borrow one, most R/C flyers own one) you can check the blade count at FANVAR 100% before you replace the fans. It would be interesting to see how much difference there is. I have seen this happen with SAAB cars, the fan motor gets tired and when it drops 15% overheating begins. Not much reserve.

100k / 5 years can be a lot of time on a fan if you spend much time in traffic. The Freestyle is not very common here in Las Vegas, so I can't say for sure what the fan life is typically. Saturn fans seem to go at 110k to 130k around here - about the time the A/T fails, a chicken / egg deal for sure.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

B,
Thanks for all of your help on this.
Will let you know how things work out with the fans.
I do like playing with the OBD scanner, but then any opportunity to invest in a useful tool is always welcome.

I found an on-line source that has a good price for the fan assembly. $145 instead of the Ford $430. I think that is enough difference to justify using the aftermarket part. It will take a week or so to get the fans. Plus other life events keep getting in the way. This is my daughters car and I loaned her my extra vehicles to use while I am working on hers so getting it running by tomorrow has not been a factor in this repair.

I agree with your comments on FANSSM, I just wish I knew what it was monitoring for sure.
Per Mitchell, the Ford docs have several holes with regard to the AC info. for this vehicle. Like no Suction/Discharge pressure curve. And missing info on several of the AC PIDs.

Referring to earlier comments....
I am confident the refrigerant is full. The system has been evacuated and filled twice. The first time we found the low charge. The second time (after the charge had been topped up) to replace the control valve. The second time it was evacuated, the charge was exactly where it was suppose to be at 38 oz. (per the tag under the hood). I saw the setting on the machine when it was recharged the second time (2 lbs 6 oz plus 2 oz for hose loss, as per the equipment spec.).


Fasto,
Thanks for your comments. I have checked the various air deflectors and foam seals around the condenser/radiator and compared what I have to the Ford pics, but will do so again to confirm. The fans while expensive on this vehicle are easy to remove. I have removed and inspected and see no obvious problem. I have the Ford pictures (through Mitchell online) of where the PCM is but I still can't see/find it. I know there are three connectors for the 150 pin PCM. Probably does not matter at this point as I don't plan to do anything with it anyway.