Automotive Air Conditioning Information Forum

2008 F150 Supercab, 5.4 engine
Truck has had a AC cooling problem since before new owner bought it.
He took it to a repair shop where it got new compressor, new condenser, orifice tube and accumulator.
Daytime ambients are 95 and 100°F.
Also new blend door actuator and crimp heater hose shut. This truck has to be driven 3 miles on the interstate to get it to cool down to 45°F. Compressor is set to cycle at 42°f. So it doesn’t ever cycle. The AC never gets the interior of truck even comfortable when driving in town. Stays around 60°F. vent temp. I added a pusher fan on the front. Did not help even a little. In the shade at 1800 RPM the high side is 175 to 200 psi. Wait several minutes and low side will pull down around 30°F. I can run the blower no higher than 4 marks on the display. That is a medium low speed.
Takes evening temperature drop to get the compressor to cycle.
I taped my digital thermometer leads on the inlet and outlet at evaporator. I got consistent 46°F.into and 44°F. out of evaporator. Low side at 30 psi. I was able to get a hole in the case and slide a thermometer into the fins of evaporator. The temps are around 47°F to 50°F or more. Could the evaporator be coated with something? Maybe a hole in the HVAC case? I can’t remember not being able to get a truck to cool. I have a 2000, F250 and a 2011, F250. Both do a fine job. I put pusher fans on the 2000 model and it will cool 40°F all the time. Even in this 100°F degree weather.

bfox wrote:2008 F150 Supercab, 5.4 engine. In the shade at 1800 RPM the high side is 175 to 200 psi. Wait several minutes and low side will pull down around 30°F.

175 to 200 psi sounds a little low for typical high side pressures. Does anybody have a spec or feel for what Ford trucks typically run for this to help him?

FS20 Scroll Compressor.

If it only makes 200 psi @ 1800 engine rpm & 95f, it is done.

Since the condenser is also the primary filter, it may be full of metal. An inspection of the orifice tube is the next step.

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Ok, So this sounds interesting. New orifice tube in the line out of condenser. I went ahead and changed it anyway. However, It was clear.
No change. 1800 RPM at 3 bar blower setting will pull down to 40°F in several minutes. Seems to take too long. With it at 40°F. Start increasing fan speed one bar, vent temp comes up to 48°F. Anymore speed the unit is unable to keep it below 55°F. Driving the truck in traffic the vent temp is 55° to even 62 up to 65°F. Something is wrong. New condenser. I'm going to pull it down and flush what I can and drain the accumulator. Frankly, I didn't ask those guys if they used flush on the evaporator. They said they blew everything out.

Postby bohica2xo » Mon Jul 03, 2017 8:18 pm
FS20 Scroll Compressor.

If it only makes 200 psi @ 1800 engine rpm & 95f, it is done.

Are you saying the compressor is bad or pushing all it can. Remember I have an extra fan running on the front.
Also,, The folks told me they installed a new Hayden E-Clutch on the radiator fan. Seems to move some air but it may or may not be good.
I have put a sprinkler up against the condenser at 1800 rpm and still have to keep the blower down on low speed. Something isn't right.
It's ike the air is moving over evaporator with no heat transfer.

If the condenser had been replaced & the O/T is clean, that leaves the compressor. Is it original?

At high heat loads you would expect higher pressures. You say it never cycles. If the evaporator had 3 coats of house paint on it, it would cool poorly - and the accumulator would fill with liquid refrigerant. The system would cycle & there would be frost on the accumulator.

You have poor cooling, low head pressure & no cycling. That is usually a compressor on it's way out, and typical of scroll units - I am not positive the F150 that year used a scroll, but others in the 2007-2008 ford line did.

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This pickup does use scroll F20 is it? Anyway, I pulled the system down and flushed the evaporator and condenser. I got clear flush back. no sign of oil. Slightly cloudy on the first quart through the evaporator. I put the truck back together and added 8 ounces of oil. Compressor was pushing 225 with 35 on low. I took for a drive and it started cooling at 40°F to 48°F. I'm going to leave this and give it back for now. Thanks for your help y'all. (For now)

Terrific.

"Never trouble trouble until trouble troubles you" - why I'm leaving my 1998 Frontier AC operating instead of grinding down the hose fittings again....viewtopic.php?f=3&t=1614&start=10