RenoHuskerDu Posted August 9, 2021 Share Posted August 9, 2021 My son's 89 F350 has about 50 psi static, which is low for 90F, but we noticed something odd right away on filling it so stopped after four oz of oil/dye and one can of R134. The oddity is identical pressure readings on the low side and high side with the compressor clutch jumped to run. This condition can be caused by an blown out orifice tube. We had drawn the system down for about 30 minutes so moisture in there should be minimal, otherwise that can cause elevated low side pressure. It held the vacuum successfully. So the system has no leaks, at least no big leaks. Following up on the orifice tube lead, I checked on Rick's Free Auto Repair I see that all F-series from 1980 to 2009 use orifice tube. Whew. So that's what we'll replace. And a receiver dryer for good measure. The system was open for a few hours and it's been humid in Texas. AC work is not all that hard so I encourage folks to try. Shops charge over $100 just to service an AC. It can be done at home. Just get you some gauges and manifold, some cans of R134, some dye/oil, and crack the books. I even repaired the AC in my Cummins 4BT grader last summer. FYI Link to comment Share on other sites More sharing options...
kramttocs Posted August 9, 2021 Share Posted August 9, 2021 Appreciate the symptom and resolution heads up Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 9, 2021 Share Posted August 9, 2021 Appreciate the symptom and resolution heads up Yes, thanks for the heads-up. Please let us know what you find. Link to comment Share on other sites More sharing options...
Machspeed Posted August 9, 2021 Share Posted August 9, 2021 Appreciate the symptom and resolution heads up Yep, working on my AC right now. Fixing to head out there and put a charge on it. I have concerns that my compressor may be worn out, so we shall see! Link to comment Share on other sites More sharing options...
grumpin Posted August 9, 2021 Share Posted August 9, 2021 Same or close pressures can also indicate a bad compressor. Link to comment Share on other sites More sharing options...
RenoHuskerDu Posted August 10, 2021 Author Share Posted August 10, 2021 Same or close pressures can also indicate a bad compressor. Yep! But that compressor just came out of a truck with a blown motor, featured in another thread. It was working fine there. Link to comment Share on other sites More sharing options...
RenoHuskerDu Posted August 10, 2021 Author Share Posted August 10, 2021 Yes, thanks for the heads-up. Please let us know what you find. A few R134 cans. Fleabay had the best price. A set of gauges with manifold. I used Harbor Freight. Decent vacuum pump. HF again for me. Small doohickey to add dye/oil. Went with best Amazon reviews. 64 pz of dye/oil, got it on fleabay. Assorted spare fittings from fleabay. That's all you need! Our orifice tube is on order and we'll keep y'all posted. It's HOT in Texas these days. Link to comment Share on other sites More sharing options...
grumpin Posted August 10, 2021 Share Posted August 10, 2021 Yep! But that compressor just came out of a truck with a blown motor, featured in another thread. It was working fine there. Ok, cool! (Pun intended!). Good you know the history. I didn’t remember if you knew. Link to comment Share on other sites More sharing options...
Nemesis F150 Posted August 11, 2021 Share Posted August 11, 2021 A few R134 cans. Fleabay had the best price. A set of gauges with manifold. I used Harbor Freight. Decent vacuum pump. HF again for me. Small doohickey to add dye/oil. Went with best Amazon reviews. 64 pz of dye/oil, got it on fleabay. Assorted spare fittings from fleabay. That's all you need! Our orifice tube is on order and we'll keep y'all posted. It's HOT in Texas these days. Great write-up and really appreciated the part & equipment list. This is another To-Do item on my list (original factory air system). And especially with more "Heat Domes" in our future! Current Heat Dome is forecasted to last another 4 or 5 days. Link to comment Share on other sites More sharing options...
Rusty_S85 Posted August 12, 2021 Share Posted August 12, 2021 If you are doing the work I strongly suggest running some AC flush through the system with the orifice tube removed. Get as much of the old oil out as you can and then add the proper charge of Pag oil for your system. If you do this you will actually notice a improvement in the AC cooling. Oil doesnt cool and for some strange reason in the old days shade trees would add a can of oil when ever they would add refrigerant citing that oil flows with the refrigerant and will come out with the refrigerant. Problem is they are adding more than the miniscule amount that will seep out with the refrigerant and then you end up with a high head pressure situation where there is horrible cooling but the pressures read good. Im going to be doing this for my truck if I can get the clamp on hoses off my receiver drier (dealer AC unit). I currently blow 58 on a 100 degree day but I want to get it right. The other car of mine I did it on I flushed it as I had a compressor lock up (was put in new about 8 years ago) head pressures are identical to what it was before with the new compressor but the AC blows so much colder than it did before. I suspect too much oil in the system from the previous people that worked on it. I also suggest looking at pag oil with the UV dye already mixed in. I picked up a large bottle of the stuff for $5 and its enough to do all my vehicles multiple times. Link to comment Share on other sites More sharing options...
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