Automotive Air Conditioning Information Forum (Archives)

peterwells on Sun July 31, 2011 2:28 PM

Year: 2008
Make: Ford
Model: Expedition
Engine Size: 5.4
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 70
Pressure High: 400

Car has 50,000 miles and ac stopped cooling. Dealer said problem was condenser. I replaced the condenser (comes with drier built in). System holds vacuum. Full charge is 3.43 lbs according to sticker. Added first three cans (12 oz each) and high side pressure was peaking to 300 psi but it was a hot day (100 F). Upon adding additional freon pressure would spike over 400. Stopped at 4 cans. AC was not blowing very cold.

Next day, 85 F, reattached gauges, started car, AC was great, high side pressure was 200 to 250 and vents in car blowing really cold, so decided to add remaining freon, high side pressure increased to 400+ and ac no longer blowing cool. Compressor is cycling on and off. Sprayed condenser with water, high side pressure decreased somewhat but still high.

Other info, all shrouds are attached to fan. Blowers inside car appear to be working fine.

I'm beginning to wonder if the original condenser failure was caused by high pressures?

Any advice appreciated, trying to get car ready quickly for last road trip before children return to school.

Peter

bohica2xo on Sun July 31, 2011 3:02 PM

That vehicle has an electric fan clutch. It should lock the fan well before 400 psi - is the fan locking up & howling?

Were these test pressures at idle, or 1500 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.

peterwells on Sun July 31, 2011 3:19 PM

Thank you for replying.

Most of the freon filling and readings were taken with the car at tickover, however increasing the RPM did not make much difference to the high side pressure. BTW nor did spraying the condenser with water.

Regarding the fan, there is something that cycles on and off and makes a howling noise - it does not stay on when the readings are high, I couldn't see what it was but assumed it was related to the fan.

Peter

bohica2xo on Sun July 31, 2011 6:42 PM

Does this vehicle have rear A/C?

-------------------------
"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.

peterwells on Sun July 31, 2011 11:03 PM

Yes, both front and rear ac's were on when filling and testing.

bohica2xo on Mon August 01, 2011 12:14 AM

Well, that narrows it down some. Since an undercharge gave cold air, It may have way too much oil in it. The question is how did that happen?

You said you took it to the dealer, and they diagnosed a condensor. Since the compressor makes 400 psi, It has not grenaded & filled the condensor with junk... so what exactly was wrong with the condensor? Did it give the same pressure readings before you replaced the condensor?

The other possibility is air in the system. Is it possible that you managed to lose the vacuum while preparing to charge?

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.

jimbob0077 on Mon August 01, 2011 8:42 AM

Didn't you say in the original post that at one point the air was cold and the high side pressure was approx two hundred and something? It wasn't until you added the last can that your problems began. So is it possible that you over serviced the system with R134? Maybe take the vehicle out on the road and run the system for a while then recheck. Maybe bleed a little R134 out of the system. Then check your pressures.

peterwells on Mon August 01, 2011 10:17 AM

Thanks for the replies,

Regarding the initial diagnosis of the condenser, the car had been booked into the dealer to have some other work done (broken seat belt) and the ac had stopped working. I asked the dealer to look into the ac and he said the system had no freon and the condenser was bad, $850. I figured it was something I could tackle so ordered the parts, the replacement was straightforward. I didn't do any diagnosis of the problem and simply took the dealer's recommendation. I do not think they filled the system and really did a full diagnosis, I don't know exactly what they did, but will check.

Re the quantity of oil in the system, this is the first time the system has been opened and I did not add oil.

Re air, I ran the vacuum pump for a few hours, it drew a vacuum pretty quickly and seemed to level out at -29.5, with the valves closed and the pump off it held pressure for a couple of hours, I then filled by connecting cans to the fill line on the manifold and opened the valve on the can. I don't see how air could have got in.

To clarify pressure readings...

When initially filling, high side pressure was OK for first two cans, however there was also no cold air coming from the vents, adding additional freon saw the high side pressure increase, initially to around 300 psi which I figured was on the high side but maybe OK (it was very hot mid day Saturday), additional freon pushed the figures higher, I stopped after 4 cans (48 oz, system capacity is 55 oz.

On the Sunday I reconnected the manifold and restarted the car, initially I was very pleased, ambient was 83F and high side pressure was moving between say 180 and 250 as compressor and fan cycled on and off (incidentally I'm not sure why the ac would cycle off, the car doors were open and the temp set to 60 F), and the ac was blowing really cold air. Great I thought and went ahead and connected the fifth can of freon. Initially it filled OK, but then the high side pressure gauge started to go higher. When I shut off the valves at the manifold the last can was empty. So now the system has 60 oz of freon in it, i.e. 5 too much.

Some questions....

Does anyone know what pressure the high side protection switch should operate at? Is it a specific pressure or dependent on temperature? Why would it even come on when the pressure is 400 psi?
Would over pressure cause the condenser to fail, I'm wondering if the condenser problem was the result of something else having gone wrong.


Thanks for you help,

Peter

mk378 on Mon August 01, 2011 10:35 AM

A diagnosis of "No refrigerant [because] the condenser is bad" would mean there's a leak in the condenser. Was there a leak in the old condenser?

peterwells on Mon August 01, 2011 11:58 AM

Re checking the condenser for a leak.

I have not tested the old condenser, nor did I try pulling vacuum on the system while it was still connected. I did not see any obvious damage on the condenser. I'll need to get some fittings to blank of the ports and apply pressure. Any ideas about where I could source these?

thanks,

Peter

peterwells on Mon August 01, 2011 5:16 PM

BTW the sticker under the hood says 1.37 lbs of freon for the front and 2.06 for the aux ac (which I'm assuming I have as there is a second ac for the rear of the car). I called a dealer and they said the aux quantity is an additional amount of freon - i.e. 3.43 lbs in total, I said I was surprised the auxiliary took more freon than the primary but the dealer said it was due to the length of the pipes. Is that right or is it just 2.06 if you have the rear ac system?

That might explain everything I'm seeing. Can someone confirm the freon needed in a 2008 EL expedition with rear AC?

thanks,

Peter

JJM on Tue August 02, 2011 12:27 AM

3.63 pounds (58.1 ounces) of R-134a with dual air, 2.50 pounds (40 ounces) without.

Joe