Weak A/C

gmac32

Member
Dec 8, 2009
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18
bellville ohio
I am trying to figure why my a/c doesn't blow that cold. It is just enough to keep you from sweating. I have put a new office tube in, new dryer, had it vaccumed down and refilled, pulled the cooling stack out and cleaned all of it, checked my clutch fan, and reset all of my actuators in the cab with my scanner. Pressures are great and everything on the scanner looks good. I am wondering if anyone ever had a weak a/c compressor?
 

2004LB7

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Dec 15, 2010
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if the pressures are good, then it's unlikely the compressor is weak. but... if the fan clutch is not hocking up properly and moving enough air then the high side can rise up giving the impression of a good compressor, but... this will also usually result in the low side being a little high too. same thing can happen with non condensables in the system too.

To help you further, you need to give us the pressures and temps of the low and high side. what level did you vacuum it to? what prompted you to replace all of those components? how much and what type of refrigerant did you put in? fill us in with pertinent diagnosis information please
 

gmac32

Member
Dec 8, 2009
288
3
18
bellville ohio
At 89 degrees today, my high side stayed around 240, the low side around 50. I used a new snap on a\c machine that vacuumed it for 15 min. I put in 1.6 lbs. I replaced those components because I had to do it on my 05 lly a long ago. The fan clutch has me wondering but it is tight and it isn't throwing any codes for it. On my scanner the desired vs actual for fan speed was off but it would catch up. My friends 15 dmax, his fan will be pretty loud at idle whereas mine is pretty quite
 

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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If the fan wasn’t pulling enough air, you should be showing higher pressures on the high side imho. Might be a touch low but I don’t think it’s the cause. Low side looks round about right as well

I think you have a blend door issue inside
 

2004LB7

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those pressures don't look too out of line for that ambient temp. how is your A/C temp and pressure if you raise the RPM up to about 1k?
 

2004LB7

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R-134a-Temperature-Pressure-Chart-002.png
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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Phoenix Az
you're low on refridgrent. i thought you were running it at 1500-2k rpm and giving pressures. Turn max a/c on, let the truck get up to temp and rev it to 1500-2k and give us the readings. That pressure chart is based on higher rpm's