Automotive Air Conditioning Information Forum (Archives)

efxengr on Fri July 20, 2012 1:18 AM

Year: 2007
Make: Ford
Model: Expedition
Engine Size: 5.4L
Refrigerant Type: 134a
Country of Origin: United States

07 Expedition w/aux rear air, 172,000 mi, well maintained.

92 deg days in south Florida I'm noticing A/C feels warm at idle but not bad under speed so I took some readings:

Engine off: 90 psi low & high, Amb 84 deg (Gauge Manifold is Mastercool brass)

doors open, a/c on max cool, fan high:
Speed 1500 rpm
Amb. 84F
Low 20psi
High 212psi
Vent Temp 58F

So I added 134a until I got the following:
Speed 1700 rpm
Amb 84F
Low 30 psi
High 275 psi
Vent temp 55F

@idle:
Low 40 psi
High 250 psi
Vent temp 59F

While @ idle or slightly higher I heard the fan clutch kick in (and wind noise), immediately the head pressure dropped to about 190-200psi, low dropped to 30 psi, and vent temp started dropping to 50F and below (48F) but didnt stay more than a few minutes.

Engine off, new high/low pressure is 96F w/ amb of 83F.

At ilde it almost looks slightly over charged. Shouldnt the fan clutch remain on at idle? How can I check or is it better to just replace? Not sure what cycles it, engine coolant temp? refrigerant head pressure? is there a way to test? IT was spinning the whole time while taking readings but there was a noticable change when it kicked in.


Thanks for any thoughts.


Edited: Fri July 20, 2012 at 7:29 AM by efxengr

bohica2xo on Fri July 20, 2012 12:15 PM

That fan clutch is an electrically actuated unit.

The actuator should control the viscous drive as well as the full lock application.

The PCM controls the fan based on data collected from things like ambient air sensors & pressure sensors.

If it is not working like it once did, then it could be a sensor issue or the viscous fluid is just worn out. You should pull the codes on the vehicle. I would recommend a Mitchell subscription for troubleshooting the fan system. If you do replace the clutch assembly, use a genuine Ford part like the Motorcraft YB3074. That part is 200 to 300 bucks depending on where you buy it.

A sensor that is bad can cause the PCM to turn the fan on late - or not at all.

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.

efxengr on Fri July 20, 2012 3:55 PM

man....whatever happened to the centrifugal clutch when you put on a pair of gloves and felt the blades for resistance to test it, then tossed it when it was bad?

Thanks, I will pull the codes and also check to see if it is being called to engage but not engaging.

The charge seemed to work well...the above numbers were taken at night in the garage. Sitting at redlights today in the heat was a world of difference but it still drifts a little at idle which could be the clutch or damper door.

One thing I noticed at idle when testing was that the vent temp would start to warm up with little or no change in pressures. Sounds like a damper door.