Automotive Air Conditioning Information Forum

My wife's '11 Fusion is not cooling as well as before. A/C system has never been serviced from new, 150K miles. With the engine set to 1500 to 1600 rpm, a quick check showed that the system was short cycling. Engine compartment was heat soaked - had just come back home from a drive. Ambient temp about 78F The low side gage was reading low (below 20 psi) but the high side gage was way high (above 300 psi). I am **guessing** the condenser was not getting adequate air flow. Cooling fan was cycling on/off as needed to keep the coolant temp in range. No visible obstruction in the fins of the condenser. Sprayed water on the condenser and the high side temps dropped down (did not record the number, still high but not as far out of range).

What is the recommended process for cooling the condenser when checking / charging a FWD a/c system? Do I need to add a box fan or two in front of the car? Should the rpm be lower when checking/charging a FWD car?

RPMs should be the same, regardless of FWD vs RWD. Your condenser is not getting enough fan by your own testing, but we would rather have numbers.
If a fan clutch, it is prolly no good with age of car. Do you have 2 OEM fans as is so common? Be sure they are both working properly. They like to give out also.
"What is the recommended process for cooling the condenser when checking / charging a FWD a/c system? "
The process is always the same....poorly functioning fans for whatever reason will impede the AC system like crazy, while having little impact on engine temp. I myself prefer a condenser fan is on at all times the comp is on. You really need to check the fan setup, and report back. The condensers job is to remove all the heat absorbed by the refrigerant from inside the car! A weak condenser function handcuffs the system.

You are reporting the desired numbers we want, but also include the vent temp. We live by full data.
We need more info.
You may also end up reclaiming, evacuating, and recharging the system to spec, but first get the condenser working the way it should.

tbirdbird:
Thank you for responding. Single electric fan. I am searching for my notes - I did the gage check a few weeks ago - I may need to redo the check to be able to give numbers if I can't find my notes.

You've been here before.

We need a good, fresh data set:
Engine 1500-1800 rpm
Hi
Lo
Ambient
Vent temp
max fan
max cool
recirc
doors open (for a full load test)
Your fan most likely has a fluid clutch and the fluid loses its viscosity over time (they typically do not last more than 3 years) When that happens, the cond does not get the air flow it needs, and the hi side goes way up. The engine will NOT overheat when this happens, but AC performance goes to hell

Report back

I was able to get back to taking new readings"

Engine 1500-1800 rpm YES
Hi 270 psi high press was 240 after 4 min run time w/ A/C on and stabilized at 270 after 15 min w/ A/C on
Lo 21psi
Ambient 81 F
Vent temp 51 F
max fan YES
max cool YES
recirc YES
doors open (for a full load test) YES
Your fan most likely has a fluid clutch and the fluid loses its viscosity over time No clutch - electric fan w/ pancake motor with fan blades directly mtd to motor shaft.

Good job on the data.
You should be able to get a vent temp closer to 42-45F
270 Hi is not terrible, but lower than that is better.
Electric fans get tired. I have changed out many.
If you have access to an IR temp gun, shoot the temp of the pipe going into the condenser and the pipe coming out. You should see a 30F drop. Those temp guns really only work on dull black surfaces. If the pipes are AL, then wrap a piece of elect. tape around the pipe.

You mentioned that you have a box fan, Try propping it up on a block close to the grill and aiming it right at the grill area and put the fan on max speed and retake the readings, report back

The other thing to try is to set your hose nozzle to mist, and mist the condenser continuously while you take readings. Report back

Thank you for sticking with this thread.

First off I found that my Robinaire vent thermometer reads 10 deg F high. So all previous reports of 50 or 51 F are presumed to be 40 or 41 F.

Went for a drive, steady 50 mph for 1 mile, all windows open, A/C on max, overcast, 80F, humid: vent temp 40 F.

I couldn't find the box fan, may have been loaned out, using a 15 inch dia fan in front of the grille. Temp delta across the condenser ranges from 36 to 41 F.

What appears to be to be short cycling to me (maybe newer cars do this) is still present. 3 sec off, 5 to 8 sec on, repeat

In your first post you note pressures over 300 psi on the high side. But on the full load test you got 270 psi. Has anything been changed between those tests?

At 150k miles without service, and a slightly low evaporator pressure my first move would be to recover the system and weigh the remaining charge.

All systems leak. A tiny amount of refrigerant loss over 12 years and 150k miles is to be expected. Being just slightly undercharged is pushing your low side down, and causing the short cycling.

I would not open the system. Those cars have block type expansion valves that have proven to be very reliable. That car should have some dye in the system from the factory. Go over the system in the dark with a blacklight. I prefer a 110v blacklight in my droplight - as many watts as you can buy at the big box store.

As a former dealer and shop owner, if you have a 12-13 year old car that is now having a low cooling output, the likelihood is that the system is a few ounces low. If you look at the connections and don't see oily residue, then it is highly likely that it is a slow leak over time as described above.

Now, if you find an oily residue, I suggest a complete inspection and new O rings, etc. However, if not, add a few ounces and bring the system back to specs.

Buying black lights and such only adds cost to the experience. If a few ounces is gone in a few months, then it is time to investigate further.

I'd venture to say that 90% of these are simply slow leaks over time as mentioned above.

And the bad advice fairy is back.

Topping up a modern system is a shade tree mechanic hack. Fix it right, fix it once.