Engine Size: 5.4
Refrigerant Type: R134A
Ambient Temp: 99
Pressure Low: 65
Pressure High: 425
Country of Origin: United States
Hi, I just put in a new compressor, condenser, orifice tube, accumulator and txv for the rear ac in my 1999 Lincoln Navigator. I flushed all o the lines plus both evaporators, replaced o rings, vacuumed(it did hold the vacuum for over an hour) and charged to manufacturers specs on oil (11 or 13oz depending on source - I went with 11oz) and 134a: 62 oz(1.76kg). My pressures at 1500 rpm are listed above and I get very mediocre cooling: like 70 degrees from the vents. I can get it down to near 60 degrees from the vents while driving it.
Something is wrong - both side are too high...plugged orifice? I thought I did my due diligence on this one...I would appreciate any advice available.
additional info: when I shut off the rear a/c , the pressures at 1500 rpm are: 55 psi low side and 350 psi high side....if this info helps at all
Also, I heavily misted the condenser for a few minutes while running and the pressures at 1500 rpm with just the front ac system on dropped to: 45 psi low side , 225psi high side, vent temps down to 56 degrees, with both systems on the high side jumped up to 275 psi and low to about 50 psi or so, vent temps didn't change much here, up to 58 or 60 degrees.
I run tests with all windows down, ac on recirculation and highest fan speed, temp gauge in the center front vent. The factory clutch fan is moving a ton of air and making noise while running, shop rag sucked right onto the condenser...engine cooling system is working well and at proper temps. I couldn't re-use the insulation sleeve that goes around the accumulator if that makes any difference.
Edited: Wed May 28, 2014 at 4:21 PM by drhill
The misting of the condenser, better cooling while driving point to an air flow problem across the condenser. I would be looking at the cooling fan clutch. Besides, with the expense you have gone thru, why not be sure. That is a large area to cool. It will take a long time to cool that vehicle at 99* ambient. 60* vents is 39* temp drop. Change the fan clutch.
Edited: Wed May 28, 2014 at 5:31 PM by Dougflas
Could be too much oil-- did the new compressor already have oil in it?
The compressor had a big sticker on it stating it had no oil in it and I tipped it over and turned it - no oil came out.
Shoot - I'll check the fan clutch but this fan blows a ton of air. anything else I can try? I'm reading that some of these trucks had an orifice tube in the condenser from the factory....mine didn't because it had rear a/c...it was in the middle of the line to the front evap (liquid line?). Could the new condenser I bought have had an orifice in it somewhere?
I thought the pre-installed OT in the condenser outlet was a GM thing-- but yes they did that for single air and you have to be sure to take it out for dual. The one and only OT for the front needs to be placed after the liquid line tees off to go to the back.
Edited: Thu May 29, 2014 at 1:49 AM by mk378
The more I research this issue, seems I have four possible causes:
1. not enough air through condenser - I'll replace the fan clutch but it blows really hard right now with no engine cooling issues. When I "misted" the system, I used my hose with a mister fitting on it and left it on the condenser, spraying around for 5-10 minutes...it was a slow drop not a quick drop like I have seen in the past with poor performing fan clutches
2. 134a overcharge - I charged via ac scale by weight as per the manual...and the service label under the hood...same quantity listed.
3. air in the system - I vacuumed the system twice for over 30 min prior to charging and purged the charge line before charging the system
4. too much oil - I flushed entire system and added the low side of recommended oil. The front evaporator kept spitting oil out even after multiple flushes and blowing it out with air many times. I figured it was good enough....everything else was dry after flushing or replaced. I do get oil residue at my gauges after checking the system... I guess it could have too much oil in it?
I will say the performance is a bit erratic. It has been best during and just after the initial charge (I have charged it twice, to confirm I did a good vacuum, no air in the system etc.) and while driving for a while. The vent temps are VERY slow to come down upon intial start up of a hot car. Even compared to other vehicles of the same size and system configuration.
Anymore ideas are always welcome!!
Thanks for all the help on this forum!
you could try to place a 20 inch box fan in front of the grillto simulate driving down the road and help the fsan clutch. Usually, misting the condenser that has a bad fan clutch makes the pressures drop like a rock.
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