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  #31  
Old 06-12-2012, 12:30 AM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,247
Quote:
Originally Posted by compu_85 View Post
I've noticed the low side pressure seems to move around a lot... like the TX valve is sticking? I got a video of it:

350 SDL AC pressure - YouTube

Any thoughts?

-J
if the txv was sticking, it would NOT fluctuate, or it would pump down into a vacuum...
the txv's job is to maintain a specific superheat value. if the load is low, the superheat will drop, so the txv throttles back the flow of refrigerant to raise the superheat back to it's set value.
raise the blower speed, and the fluctuating will stop.

the value is not to hold a certain vent temp, it's to maintain a specific amount of heat rise over the vapor pressure of the refrigerant in the evaporator. if the vent temps are high, either the heat mix is high, or the refrigerant volume is high.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
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  #32  
Old 06-12-2012, 12:31 AM
vstech's Avatar
DD MOD, HVAC,MCP,Mac,GMAC
 
Join Date: Mar 2006
Location: Mount Holly, NC
Posts: 26,247
Quote:
Originally Posted by emerydc8 View Post
I am at a disadvantage because the high pressure connector on my manifold gauge set broke while I was refilling the system and all I have right now is the low side reading. This is the second set of gauges that had the high side break. I guess you get what you pay for with these cheap Chinese products. Using it maybe once a year is difficult to justify buying a good set for $300 but I am almost there. I hope the fluctuation on the low side is normal.
I have dozens of sets of high quality forged brass manifolds that I do not use because the hoses are dirty for my work.
new hoses are the same price to me as new sets of manifolds...
anybody want any of my sets?
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #33  
Old 06-12-2012, 05:36 AM
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Join Date: May 2007
Location: Arizona
Posts: 757
JamesDean: Thanks for the info. I bookmarked the site. Looks like they have some good quality tools there.

Vstech: I actually need the hoses, but if you are interested in selling one of your manifolds with the dirty hoses, I would be interested. Can the hoses be cleaned to use in an auto application? How dirty can they be?
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  #34  
Old 06-12-2012, 08:07 PM
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Waiting for his Model 3..
 
Join Date: May 2008
Location: Springfield VA
Posts: 5,174
Quote:
Originally Posted by vstech View Post
...or the refrigerant volume is high.
This was the problem. I put in too much gas. Letting a bit out brought all the pressures down, cooling is better. It's super humid here today (77*, 88% humidity). At 1000 rpm i was able to get 48* vent temps with water pouring out of the evaporator drains (almost a constant stream!).

EDIT: I just checked the chart... it says vent temps should be about 55*F. Woohoo! Working better than factory!

Thanks for your input

-J
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1991 350SDL. 230,000 miles (new motor @ 150,000).

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