Model: Grand Marquis
Engine Size: 4.6
Refrigerant Type: R134a
Ambient Temp: 90F
Pressure Low: 40-48
Pressure High: 250-300
Country of Origin: United States
Hello all. My car's cooling performance has been slowly deteriorating since I bought it three years ago. 1/2 lb of refrigerant was added at a shop within the first year. 2 summers later(last summer), I found it to be a bit low so I added a 12 oz can and brought it's performance back up. But it still didn't cool as well as I thought it should. The pressures after adding that can were good if I recall so I don't think I overcharged.
Now, it's not working so well once again. On MAX, it will keep me cool, especially when the car is moving. On NORM, it's virtually useless. The air is clammy and not that cool. NORM has never worked very well in this car.
So I hooked up the manifold set today and found the above listed pressures with the system on NORM, doors open, engine at idle. Humidity is about 55-60%. The dash vent temp is 62F. The compressor was running constantly. The accumulator is not sweating at all.
I then tried MAX, doors open, 1800RPM. Highside 300-325, lowside 25-35, vent temp 50-55F. The accumulator was now sweating and actually felt coldish. I'm no expert but those pressures seem kinda high. I then sprayed water on the condensor and the pressures dropped to 200 or less and the compressor started to cycle rapidly. Vent temps actually climbed because the compressor was off for several seconds at a time.
What's going on here? In my amateur opinion, I don't think it's low on refrig. The compressor gets a little noisy after it's been on awhile. Is my system just worn out? There is tons of airflow from both the clutch and electric fans. I've noticed the A/C puts more drag on the engine than it used to although it could be my imagination. It IS 13 years old now so perhaps it's in need of some investment.
Edited: Fri June 13, 2008 at 5:02 PM by mrbear3800
The water on the condenser test, and also that you get better performance when moving shows that your condenser airflow is not good enough. May need to clean out dirt and bugs from the fins. Check that all shrouds and baffles are in place. And the fan clutch most likely is weak.
When the condenser is working better you might find it is actually undercharged. The only way to be sure of a proper charge is pull it all out and recharge with the manufacturer's specified amount.
The CCOT system should cycle back on before the low side climbs to 50 psi. If it doesn't, try a new cycling switch.
If you've been adding refrigerant, you obviously have a leak, if not you can be overcharged. I would try to find and fix the leak, if you can't find it, I would still evacuate and recharge either system into a deep vacuum to factory specs. You could have air in the system causing high pressures and poor cooling. You need to know the system is properly charged before going any further..Hope this helps.
Freedoms just another word for nothing left to lose
I think I'll pull the radiator and clean the condenser first. I'm not too enthused about taking it to a shop and paying over 100 bucks for them to evac, recharge and proclaim it fine. Not yet at least.
As far as finding leaks, I have not noticed any signs of oil at the fittings that I can see from the top. Is it common for these FS10 compressors to leak? A line that runs near the wheel well is VERY corroded but I can't see any signs of oil on it.
And finally, my voltages drop down quite a bit at idle with the A/C on, as low as 12 volts. The battery is newer and the alt is good. It doesn't do this with the A/C off. Can the A/C clutch draw too much power when going bad?
I'm seriously considering just replacing the compressor/clutch, accumulator, orifice tube, various o-rings, and that rusted line. It's old and could probably benefit from it.
Edited: Sat June 14, 2008 at 6:15 PM by mrbear3800
let us know how it goes
Uhh, sorry about the multiple posts. Don't know how I did that. Can a mod delete those please? lol
I realize it will cost more to replace that stuff but I don't want to pay for the evac and recharge twice. In other words, I don't want to have that done and then find out later I have to replace parts. Last time they evac'd and recharged, it helped but not much.
Edited: Sat June 14, 2008 at 7:07 PM by mrbear3800
I finally pulled the radiator and cleaned stuff up. The bottom front face of the radiator was virtually blocked with leaves, dirt, bug parts, and those fuzzy floating seed things....
I set the radiator across saw horses and directed a hose at the back side of the radiator. BLACK water was coming out of those fins! Even the parts that didn't look dirty and I could see through easily. I then soaked it all in simple green and then hosed it again. Lots of brown water still.
I obviously cleaned the condensor in-car. I didn't get the same crap coming out of it when i hosed it. It seems almost everything passes through and jams on the rad. I did as much brushing of the front side as I could. The bottom 1/4 of the condensor is pretty beat up, though.
Anyhow, the A/C SEEMS to be working a little better now. I used AUTO and let it do it's thing and even when it switched to NORM, the air was still pretty cool. I did notice the compressor cycling a bit more so perhaps it was a little low on refrig after all. I'll do another pressure test when I get a chance.
Also, the engine runs a bit cooler now. In 80-85 temps, it would run at 193-197 mostly. Now it's 188-193.
Not long after cleaning the condensor/radiator, I did another pressure test and found it to be marginal, as one of you predicted (borderline low charge). So I added about 2/3 of a can and it is working great. Gets down to as low as 38 degrees when cruising if I let it. I still think the system needs a "refresh" but it's good enough to get me through the summer. Thanks!
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