2000 Excursion Rear AC Issues

[hbabler]

Okay I need some advice:

2000 7.3 Excursion. Towards the end of last summer it got a new condenser, Compressor, orifice tube, dryer, heater cut off valve, blower and front evap. It was charged by weight and worked fairly well. It’s now hot here and it’s not cooling as well as it should when the rear Ac is on.

Today it was 99 and I took some readings.

1200 RPM, front only on Recirc, 44 low and 270 high

All on: 1200 RPM 64 low, 325 high

I misted the condenser with water and it dropped the high to about 260 but the low didn’t change.

Any ideas on what’s going on here? I know I’m asking a lot of the system on this truck as it’s hot but I want it to be as cold as possible. When I have passengers and it’s hot it’s pretty miserable. Thanks so much for the help!

[Dougflas]

Recover the charge and weigh the total correct charge back into the system. You may have a marginal TXV at the rear evap. Was it changed?

[hbabler]

I did not change it. Do you think it’s worth changing?

[bohica2xo]

Was that pressure drop to 260 psi from the 325 psi situation?

If so the fan clutch is suspect.

[hbabler]

Yes it dropped from the 325 when I misted the condenser. I have a fan clutch in the garage which I haven’t installed due to the truck not overheating.

Could the new clutch help the low side pressure as well?

[Cusser]

Yes it dropped from the 325 when I misted the condenser. I have a fan clutch in the garage which I haven’t installed due to the truck not overheating.

When my '98 Frontier developed a pinhole in its high pressure line on a 119F afternoon a few years ago, I also found that its fan clutch was bad, and my engine was not running hotter than usual at all. I had no idea until a couple of days later until Mrs. Cusser left it idling with the AC on for like 10 minutes.

[bohica2xo]

When a fan clutch wears out it usually has enough drag to cool the engine under most circumstances. The heat load on the A/C goes way up, and compressors take a beating.

Low side pressures will drop if the liquid going to the evaporators is cooler. There is always a higher low side pressure when a lot of heat is being recovered. It was 114f here yesterday. When I started my car the compressor delivered as much liquid to the evaporator as always, but the gas in the suction line was heated to about 90f - so the low side would probably have been around 100 psi if I checked it then.

Change the fan clutch.

[hbabler]

Okay I replaced the fan clutch. It’s better and it may be as good as it’s going to get but I hope I can get it a little cooler.

91 ambient.

1200 RPM
Front only:
43 Low
247 high

Rear and front AC on high recirculate
55 low
250 high

Is this acceptable performance for an excursion?

Any ideas what I could do to make it a little better? My concern is that on a 100 degree day it’s not going to do as well as I want it to.

[Tim]

Seems like good readings for dual unit lots of windows.

[bohica2xo]

Excursions were huge. Large interior volume, and lots of glass as Tim pointed out.

It will cool down, but it will take a few minutes. Recirculate is your friend. Go for a 30 to 40 minute drive someplace. You will pull the cabin down to a comfortable level before you know it. That is why here in Las Vegas, the limos, Suburban's etc idle endlessly. Once they get them cooled down they keep them that way for the next customer. I think the only time a police car in this town gets turned off is for an oil change.

112 today when I left the shop. 2007 Saturn Vue, locked up in the sun since 0800. HOT inside. Drop the windows, cabin fan on max and drive off. One block later raise the windows. Manage transmission to maintain 2000+ rpm in traffic (effing scroll compressor). 2 miles later cabin is under 85f, and dropping. 15 minutes to a comfortable cabin.

Dropping the windows is important. The air & plastic interior is about 140f when you open that door. Exchanging air at 112f is a win for a minute or two.