Wildblue19
I'm Awesome
Hey everyone. Unique A/C question on orifice tubes for my 1993 GMC 5.7 4x4 Suburban. TLDR, AC sucks and I took off my condensor lines and there was no orifice tube - straight up empty pipe. Put one in and negligible changes in vent temps. Is having no orifice tube intentional for rear air trucks?
Backstory: In south Texas, it's been over 100 for about a month straight. Prior to moving down here, I had pre-emptively rebuilt the entire A/C system and converted to 134 from R12 which was not working. I made custom lines, flushed all the hoses, completely took apart and cleaned the rear air system and TXV, installed a sanden compressor, new parallel flow condensor up front, and changed all O rings. Vacuumed down for an hour, checked for leaks and charged with 4# of 134 and about 8oz (don't recall exact amount) of oil. Worked fine for Colorado summers.
Fast forward to living in Texas, I felt that the A/C in my truck was lacking, with vent temps for a 105° day with 30% humidity around 75°. Tested high/low side pressures, and before taking the system apart I saw 50/245psi. This seemed reasonable, but dissatisfied with this performance I opted to install a VOV to replace whatever factory one came in the condensor.
Took the condensor lines off today and to my surprise, the condensor had no orifice tube. I thought the condensor came with them installed, and didn't check on initial install (I know, shame on me). I put the VOV in today and vacuumed down, checked leaks, and charged with 4# again. Vent temps are pretty much the same, perhaps 2-4* cooler, for both front and rear air. Pressures changed slightly to 55/240 for a 102* 20% day.
My questions:
1) for rear air trucks is the orifice tube left out? Perhaps the rear TXV handles the front and rear systems?
2) is a delta T of 30 degrees or so the limit for these trucks? With front VOV and rear TXV the best I've seen is about 32* Delta T.
Maybe an e fan is the answer, but I don't see much change from idle to highway, maybe 4 degrees. Any input is appreciated to include data points on other suburban drivers vent temps and pressures. Thank you!
WB.
Edit, been looking around and local expert @L31MaxExpress may be able to shine some light upon the situation. My sanden unit is part # 4864 and the VOV is 38905.
Backstory: In south Texas, it's been over 100 for about a month straight. Prior to moving down here, I had pre-emptively rebuilt the entire A/C system and converted to 134 from R12 which was not working. I made custom lines, flushed all the hoses, completely took apart and cleaned the rear air system and TXV, installed a sanden compressor, new parallel flow condensor up front, and changed all O rings. Vacuumed down for an hour, checked for leaks and charged with 4# of 134 and about 8oz (don't recall exact amount) of oil. Worked fine for Colorado summers.
Fast forward to living in Texas, I felt that the A/C in my truck was lacking, with vent temps for a 105° day with 30% humidity around 75°. Tested high/low side pressures, and before taking the system apart I saw 50/245psi. This seemed reasonable, but dissatisfied with this performance I opted to install a VOV to replace whatever factory one came in the condensor.
Took the condensor lines off today and to my surprise, the condensor had no orifice tube. I thought the condensor came with them installed, and didn't check on initial install (I know, shame on me). I put the VOV in today and vacuumed down, checked leaks, and charged with 4# again. Vent temps are pretty much the same, perhaps 2-4* cooler, for both front and rear air. Pressures changed slightly to 55/240 for a 102* 20% day.
My questions:
1) for rear air trucks is the orifice tube left out? Perhaps the rear TXV handles the front and rear systems?
2) is a delta T of 30 degrees or so the limit for these trucks? With front VOV and rear TXV the best I've seen is about 32* Delta T.
Maybe an e fan is the answer, but I don't see much change from idle to highway, maybe 4 degrees. Any input is appreciated to include data points on other suburban drivers vent temps and pressures. Thank you!
WB.
Edit, been looking around and local expert @L31MaxExpress may be able to shine some light upon the situation. My sanden unit is part # 4864 and the VOV is 38905.
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