Automotive Air Conditioning Information Forum (Archives)

thompsdw on Sat July 09, 2011 12:00 PM

Year: 2004
Make: Ford
Model: Expedition
Engine Size: 5.4L
Refrigerant Type: 134a
Ambient Temp: 90
Pressure Low: 25
Pressure High: 335
Country of Origin: United States

Hi everyone. Nice forum. I live in Houston, TX so high heat and high humidity load. I know this vehicle takes some time to cool because of interior space, but my at idle cooling is not up to par and I would hope the register temp on the road would be a little colder. On the highway, I have seen temperatures as low as 47 F at the center register. I did recently add one can of 134a (~19 ounces) recently to help out. I charged off suction pressure alone, and just purchased a set of gauges to get the "right" picture. Any help would be appreciated, please ask for more information if needed.

Common facts:
- Discharge pressure takes some time to equalize
- Original fan clutch is installed on Expedition with 50M Miles
- Oil color is fluorescent YELLOW. I am the second owner, is this color normal or did someone add a dye prior to my owning? I have had it for about 5 years.

1,500 RPM
- 89 F Ambient
- 52 F Center Register Temperature
- 25 PSIG Suction Pressure
- 325-350 Discharge Pressure (cycles slowly)
- No clutch noise

850 RPM
- 55 F Ambient
- 52 F Center Register Temperature
- 32 PSIG Suction Pressure
- ~250 PSIG Discharge Pressure
- "Pinging" Clutch Noise at this RPM




Ambient T:

thompsdw on Sat July 09, 2011 12:04 PM

Sorry, messed up a few numbers on the 850 RPM set:

850 RPM
- 89 F Ambient
- 55 F Center Register Temperature
- 32 PSIG Suction Pressure
- ~250 PSIG Discharge Pressure
- "Pinging" Clutch Noise at this RPM

JJM on Sat July 09, 2011 12:55 PM

At minimum, you should recover the refrigerant, vacuum, and charge to spec - 54 oz for dual air. Even better, not knowing the full history of the vehicle, flush the system, replace the accumulator, inspect and replace the OT, replace the associated o-rings, add 14 oz of PAG 46 oil, vacuum and charge 54 oz of R-134a.

Discharge pressures are high even at 90F. Are the condenser fans operating properly? All the air deflectors in place? Are the condenser and radiator fins nice and clean? If this things hasn't been a mall queens and done a lot of off roading, there might be a bunch of gunk between the condenser and radiator.

I love Texas... huge, red state, guns, big trucks, 80 MPH speed limit in the western part (and looking to increase it to 85 MPH)... it's what America is all about... not these stupid little "green" cars and energy conservation. I'm definitely not living in the right state.

Joe

bohica2xo on Sat July 09, 2011 1:03 PM

Everything JJ says is right on the money.

I will offer one small shortcut. Duct tape.

hook your gauges up, and duct tape them to the windshield so you can read them from the passenger seat. Have someone else drive, and record the gauge readings above 50 mph, and 2000 engine rpm - along with the vent temp at the same time.

Your fan clutch is probably tired, and even a mall queen in TX will have a condensor full of bugs.

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.

iceman2555 on Sat July 09, 2011 2:45 PM

The pressures indicated with this post indicate more than a possible charge issue...but the great possibility that the compressor has already begun to fail. The excessive discharge pressures indicate a restriction in the inlet side of the condenser. This vehicle utilizes a scroll design compressor and these are known for condenser contamination. The elevation (100 psi) of DISCHARGE (gas) pressures...not LIQUID pressures is a strong indication of this restriction.

One could follow suggestions posted by JJM, the first and foremost diagnostic procedure is to FULLY charge the system. Think this would be a great pre evaluation of the system. Suggest to do this without changing the suggested parts......insure that all system are functioning properly. If all is well...compressor operation....condenser temp drops are acceptable....the discharge pressures decrease.... (hopefully no pressure increase)...then recover the refrigerant...flush the system and service accordingly. I would wish to know for sure all is well prior to the extra labor and parts that would have to be redone.

Charge the system and then perform a temp drop test on the condenser...Max Cool, Blower speed on high, Doors open, Engine at idle speed. Allow the system to stabilize...app 7-10 minutes of operation and then test the evap inlet and outlet temps....should be within 3-5 degrees of each other....then test the condenser inlet and outlet temps....if all engine cooling system components...are functioning correctly...should be 24-29 degrees. Excessive temp drop would indicate a inlet restriction. A minimal restriction would indicate a possible charge issue or a cooling system component failure....external condenser air flow restrictions....weak fan clutch....etc



-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

bohica2xo on Sat July 09, 2011 3:15 PM

Did not realize they had started putting that crappy scroll junk on that vehicle too. The "Ping" is probably just the nasty pressure spike from the scroll that happens every revolution - much less obvious at high rpm.

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.

iceman2555 on Sat July 09, 2011 3:34 PM

These damn scrolls are great as long as they are lubricated properly, but will fail in an instance. There is not a day that goes by that the repair issue of this compressor does not result in a call on my phone. And they are using more of them from various manufacturers.......like a virus....spreading.

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

bohica2xo on Sat July 09, 2011 6:54 PM

A scroll is just fine in stationary refrigeration, coupled to a constant speed driver, running in an oil bath. The ski jump like output curve gives poor idle performance, especially with the fords that were driven almost 1:1 with the crankshaft.

The dodge B van with the 105 scroll did a little better with the 2.4:1 overdrive at least.

The fact that they tend to fail very quickly if they fall below critical charge is exacerbated by a bunch of engineers that leave no reserve in a design - vehicles that used to hold 72 ounces of refrigerant now hold 32.

I guess I should be happy that the plan is run to failure, then replace everything.

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.

thompsdw on Sat July 09, 2011 7:23 PM

So, if I am going to keep this a while in hot country - I am hearing change the compressor, the dryer, and OT (orfice tube - JJM what is this, sorry!!!). I would rather do this once and not screw around a new compressor is $300. Is is common to find shops that will recover and hold the charge and let me do the work????

I have been burned with quality of workmanship before, I prefer to do my own work.

Edited: Sat July 09, 2011 at 7:23 PM by thompsdw

bohica2xo on Sun July 10, 2011 1:09 PM

With an uncertain charge level, I would want to see a proper charge weighed in for testing.

It is a 134a system, so recovery & recharge is no big deal. No reason to "hold" anything, your old refrigerant just gets recycled.

With a proper charge on board, you can do the highway test & full load test (2000 rpm, cabin fan on highest speed, doors open) and decide where the issues are.

Condensors get dirty. Bugs & road dirt can rob performance. A deep cleaning with a strong surfactant like Simple Green or Zep Orange will get a lot of that out. With a cold condensor, spray the full strength cleaner deep into the fins. Let it stand for a few minutes, then rinse with a garden hose. You may be surprised at what comes out. You should also inspect the space between the condensor & radiator for debris.

Your compressor may be fine right now. It will not last very long without proper charge levels, or working against a dirty condensor or tired fan clutch.

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.

iceman2555 on Sun July 10, 2011 9:27 PM

If you replace the compressor...insure that the condenser is replaced also. The system should be thoroughly flushed and cleaned....front and rear. Minimal amounts of debris remaining in the system may result in premature compressor failure.
Have the system professionally recharged....and undercharge will result in a repeat failure.
Good luck

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

thompsdw on Mon July 11, 2011 10:13 AM

Thanks for all the advice. Couple more questions please?

1) What should the discharge pressure be at idle (it is 250 PSIG now)?

2) Is the "pinging" noise I hear from the clutches a normal noise at idle (doesn't happen at 1,500 RPM).

thompsdw on Mon July 11, 2011 12:04 PM

Let me say a little more ....... I am fairly normal at idle on discharge pressure. What I don't understand and need some help on is how much the discharge pressure should vary with RPM? If it varies, then at what RPM should I be checking. Mine has a 100 psig swing in pressure from what I can see from idle to speed.

bohica2xo on Mon July 11, 2011 5:19 PM

Normally full load testing is done at 2000 engine rpm. Doors open, cabin fans on highest speed. This gives the worst case load - which can happen driving off from a parking lot after a few hours in the sun.

Let it stabilize for a couple of minutes, then record the pressures while still at 2000 engine rpm. It should not cycle - unless it is cycling on the HPCO...

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.