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Username Post: Evaporator replacement        (Topic#351881)
Kyled1986 
Poster
Posts: 22

Reg: 07-05-18
07-17-18 04:34 PM - Post#2740335    
    In response to beagrizzly

This method makes sense to me. I love the way you described it. If I hadn't already charged the system I'd try it. The temperatures I mentioned earlier I cannot seem to replicate neither at idle or highway speeds. When I got to thinking about it I realized while I was charging that I had a fan in front of the condenser and I was continuously spraying it with a water hose to get the system to take the vapor refrigerant. Every since then I have not been able to achieve those same temperatures at the vent. What I do remember is that my head pressure upon stopping the charging process was approximately 160 psi and it was a 95 degree day.
I'm not so sure that I'm not undercharged. What is an appropriate head pressure reading at a 90 or 95 degree ambient? Better yet is there a formula? I know for a fact I don't have a leak and I also know I have adequate airflow over the condenser. I can't check Evap inlet and outlet temps because the orifice tube is installed at a point where half of it is in the engine compartment and the other half is in the Evap box.

By the way...i charged 32 oz into what the OE says is a 44 oz system.



Edited by Kyled1986 on 07-17-18 04:36 PM. Reason for edit: No reason given.

 
rockfangd 
"7th Year" Gold Supporting Member
Posts: 2870
rockfangd
Age: 34
Loc: Utica ny
Reg: 04-13-10
07-17-18 07:44 PM - Post#2740357    
    In response to Kyled1986

Hmm.
high side is always 1.5 times the ambient temperature
So on a 90* day it would be 90+90+45= 225 psi on the high side.
You may be undercharged.
What is your vent temp currently?
So you put 2.0 lbs which is 32 oz
2.75lbs is 44 oz so if that is correct you are undercharged .75lb. Which is enough to make a difference

Old School GM fan FOREVER


Edited by rockfangd on 07-17-18 07:50 PM. Reason for edit: No reason given.

 
Kyled1986 
Poster
Posts: 22

Reg: 07-05-18
07-18-18 02:56 AM - Post#2740376    
    In response to rockfangd

Thank you. The 1.5 is the number I thought I remembered. Yep, I put 2 lbs exactly in there. I shut the bottle off as soon as the scale read that amount. Originally, GM claims the r-12 charge is 44 oz or 2.75 lbs like you said. My new ac kit came with a charging chart that showed the charge should fall somewhere in between 70% which was 30 oz and 80% which is 36 oz or so. I stopped at 32 oz because I felt I was getting plenty cold vent temps at that point. I was getting 36 at the center vent with blower on max, recirculate on, Windows up, and motor revved to 1200. That was when the head was 160. Now, if I drive the truck down the highway for 15 to 20 minutes in the same heat (95*) I can get to maybe 43-44. At a base idle if I let it run long enough it will get down to 50 at about the best. I know I don't want a very high head pressure but I also know I need a high enough one to deliver as much liquid as possible to the orifice. Also of interest is that at an idle I can hear the orifice tube hissing under the dash. If I raise the idle just a bit the sound goes away. Is this an indication of not enough liquid refrigerant entering the orifice?



 
bowtie44s 
Valued Contributor
Posts: 4283
bowtie44s
Age: 37
Loc: wv
Reg: 08-29-12
07-18-18 09:40 AM - Post#2740404    
    In response to Kyled1986

I have always heard 75% 134A of the specified r12. That comes out to 33oz and the gmt400s that came with 134A calls for 2lbs. What is your low side pressure? If it's high, your compressor is bad. If not you are probably just low.

Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
Kyled1986 
Poster
Posts: 22

Reg: 07-05-18
07-18-18 11:46 AM - Post#2740415    
    In response to bowtie44s

Low side pressure when? At idle? At a certain RPM? As soon as I crank up the AC or after running it for a certain amount of time? Windows up/Windows down? Blower Speed? I always wonder what the conditions are when I read about someone having a certain pressure because we all know these variables can substantially change the readings.
I want to think that the day I charged the system and it was producing 36 degree air that it was right at 20 PSI. Oh and that was with engine at 1200 RPM, blower high, Windows up after I'd been charging for like an hour lol



Edited by Kyled1986 on 07-18-18 11:50 AM. Reason for edit: No reason given.

 
Kyled1986 
Poster
Posts: 22

Reg: 07-05-18
07-18-18 11:52 AM - Post#2740416    
    In response to bowtie44s

What is a gmt400 btw? I've seen the term but never asked what it meant



 
454cid 
Valued Contributor
Posts: 3141

Age: 47
Loc: West Michigan
Reg: 02-18-12
07-18-18 12:42 PM - Post#2740420    
    In response to Kyled1986

It's the truck platform that our trucks are. It tells more about the truck than the year, especially at the beginning or end of that line of trucks. For instance, I have a 99, and everyone knows the GMT-800 started in 99... except, my 99 is a GMT-400, not the 800. The 1-ton's weren't GMT-800s until 2001. If someone says they're working on a GMT-400, there's no room for "well, is that the old body style, or the new body style?". Unfortunately, many people don't know GM platform names.

GMT-400 > GMT-800 > GMT-900 > GMT-K2xx > T1 (2019 I believe) > T2 (in early development?)

The GMT-400 is referred to by many as the 88-98 style, but some earlier Squarebodies (73-87) were still being built through 91... crew cabs, and SUV's.

The GMT-400 was built through 2000. In 99 when the GMT-800 Silverado was made available, it was only 1/2 tons, and light 3/4 tons, the heavy 3/4 and 1-tons were still GMT-400s, and I believe a few GMT-400 1/2 tons were available too. SUVs were GMT-400s through 99... I think.

Also note, that starting with the GMT-800 "Silverado" became a model designation, where it had only been a trim level.

99 K3500 RCLB


Edited by 454cid on 07-18-18 12:58 PM. Reason for edit: No reason given.

 
Kyled1986 
Poster
Posts: 22

Reg: 07-05-18
07-18-18 06:05 PM - Post#2740452    
    In response to 454cid

Thank You! That was a very detailed description. Now I know. I have never understood why GM didn't just bring the new body's in all on the same day...1/2 ton and up all at once.



Edited by Kyled1986 on 07-18-18 06:05 PM. Reason for edit: No reason given.

 
rockfangd 
"7th Year" Gold Supporting Member
Posts: 2870
rockfangd
Age: 34
Loc: Utica ny
Reg: 04-13-10
07-18-18 06:17 PM - Post#2740454    
    In response to Kyled1986

Could be just me but I say you are fine with what you have in there now.
The temps are good for the atmosphere.
I would leave it alone and enjoy it

Old School GM fan FOREVER


 
454cid 
Valued Contributor
Posts: 3141

Age: 47
Loc: West Michigan
Reg: 02-18-12
07-18-18 06:31 PM - Post#2740456    
    In response to Kyled1986

  • Kyled1986 Said:
Thank You! That was a very detailed description. Now I know. I have never understood why GM didn't just bring the new body's in all on the same day...1/2 ton and up all at once.



Your welcome.

I would assume changing all truck variations over at once on multiple lines in multiple facilities would be a huge task. Plus the engineering on all variations of the new model may not be done all at once.

99 K3500 RCLB


 
bowtie44s 
Valued Contributor
Posts: 4283
bowtie44s
Age: 37
Loc: wv
Reg: 08-29-12
07-19-18 08:12 AM - Post#2740524    
    In response to Kyled1986

  • Kyled1986 Said:
Low side pressure when?



What is your low side pressure when the high side is 160?

Jeff

'88 Chevy K3500, aluminum head roller cam 511in³ stroker 10.5:1 compression, 96 NV 4500, 94-98 grille, 305/70-16 (33x12) BF Goodrich KM2s, 91 cluster swap


 
Kyled1986 
Poster
Posts: 22

Reg: 07-05-18
07-19-18 01:16 PM - Post#2740546    
    In response to bowtie44s

It was 18 to 20 PSI. I just realized that I had the LP switch jumpered out the whole time while I was charging allowing it to pull the pressure down so low while I was trying to add vapor refrigerant. Maybe that explains why it would get so cold that day but not now?



 
jimshoe52 
Poster
Posts: 72

Loc: Texas
Reg: 01-08-12
01-30-20 10:20 AM - Post#2785459    
    In response to someotherguy

Great pictures and advice. I'm not that auto-inclined. Just curious, what would be the cost to replace evap coil in '90 Chevy C1500?



 
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