A/C questions, newer car - Page 2 - Chevelle Tech
Misc (NON CHEVELLE AUTOMOTIVE TECH) This section is for the Non-Chevelle Related automotive questions/answers or discussion.

 5Likes
Reply
 
LinkBack Thread Tools Search this Thread Display Modes
post #16 of 20 (permalink) Old Jun 29th, 20, 4:32 PM Thread Starter
Lifetime Premium Member
Tony
 
Join Date: Apr 1999
Location: Folsom, CA
Posts: 17,351
Garage
Well, I just tried starting the truck cold so the heater isn’t a factor... no cold air, 95 at the vents before starting and after... truck is sitting in the sun.

I did notice the sound and airflow changed when switching from Cold to Hot ( Blue to Red), which would seem to be the blend air door functioning. I could clearly hear the air flow change. I could feel it but not as apparent.

Didn’t matter which vents; dash/ floor/ defroster... all had the same noticeable change in sounds from Cold to Hot or Hot to Cold...

I put the orifice tube and a few other pieces in my “cart” for Rock Auto. Not going for a compressor or anything expensive now...

I am also going to visually check for leaks. I already had a small bottle of oil and a Pringle’s kit and the receiver/ dryer ( accumulator?)

But the project is on hold for now. I have too much on my plate, and only tried because I had the manifold gauges for the Camry..

Thanks everyone

Once you go RAT, you never go back...
TC #1366

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Sold

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Sold
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
&
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
1966_L78 is offline  
Sponsored Links
Advertisement
 
post #17 of 20 (permalink) Old Jun 29th, 20, 7:19 PM
Tech Team
 
Join Date: Oct 2019
Posts: 299
Re: A/C questions, newer car

Quote:
Originally Posted by Dean View Post
28PSI suction pressure is way too low for normal operation.
Freezing pressures temperatures of low side and refrigerant
*** R12 factory fitted GM systems that use suction throttling valve [POA valve ] operate at 30PSI
***R134a freezing pressure temp 28 psi

In modern systems As automotive systems are a total compromise ie have variable suction line pressures due variable engine RPM constant rpms pressures are a myth . The thermostat saves the modern evaporator from freezing . The Tx valve plays a role but to a lesser degree.

At idle the compressor is hardly working . Pressures need to be taken at 1200rpm or higher . Often the TX valve can be seen operating and often during thermostat cycling the low side will dip well below 30psi all be it briefly .

Car makers use the low pressure cold temps [below ideal] to assist cooling. Many evaporators are to small for the job . This saves the car maker money .Effectively cheating the system .

Well designed systems donot have compromises and work very well in ALL ambients .
----------------
Operating pressure ideally ,,not always achieved
Low.... no lower than freezing pressure/temp of refrigerant
High... relevant to how hot ambient is,, ideally = 115f = 150-160psi
swampy 6x6 is offline  
post #18 of 20 (permalink) Old Jun 29th, 20, 9:07 PM
Gold Founding Member
Administrator
 
Join Date: Aug 1998
Location: near Kansas City
Posts: 62,783
Garage
Re: A/C questions, newer car

Quote:
Originally Posted by swampy 6x6 View Post
Freezing pressures temperatures of low side and refrigerant
*** R12 factory fitted GM systems that use suction throttling valve [POA valve ] operate at 30PSI
***R134a freezing pressure temp 28 psi

In modern systems As automotive systems are a total compromise ie have variable suction line pressures due variable engine RPM constant rpms pressures are a myth . The thermostat saves the modern evaporator from freezing . The Tx valve plays a role but to a lesser degree.

At idle the compressor is hardly working . Pressures need to be taken at 1200rpm or higher . Often the TX valve can be seen operating and often during thermostat cycling the low side will dip well below 30psi all be it briefly .

Car makers use the low pressure cold temps [below ideal] to assist cooling. Many evaporators are to small for the job . This saves the car maker money .Effectively cheating the system .

Well designed systems donot have compromises and work very well in ALL ambients .
----------------
Operating pressure ideally ,,not always achieved
Low.... no lower than freezing pressure/temp of refrigerant
High... relevant to how hot ambient is,, ideally = 115f = 150-160psi
You obviously haven't charged up a R134a system using the suction pressure as a gauge.

I've usually always evacuate the system and weigh the charge in and with the exact amount in, the suction pressure is NEVER even down close to 28 psi on a R134a system.

You seem to talk about everything except what these threads/posts are actually about which only confuses folks.

There is no expansion valve (or R-12) in a modern orifice tube R134a system.
LeoP likes this.

.
.
.
.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Dean is offline  
 
post #19 of 20 (permalink) Old Jun 30th, 20, 6:09 AM
Tech Team
 
Join Date: Oct 2019
Posts: 299
Re: A/C questions, newer car

HI
Dean the OP was in question as to what Low/high pressures should be . So yes it was discussed .

Servicing A/con is way way more than squirting refrigerant in . Did u no that auto aircon comes inboth t/X valve and orifice tube !!. Even in the same model of car R12 or R134a .
I guess with an EPA government refrigeration license and experience of 35years plus ,might just no some thing !!
I have explained superheat and subcool together with other parameters on how to properly charge a system in other threads . I suggest u read these b4 u comment in future .
Oh yea a tx valve system is commonly filled to subcool and superheat spec using the low/high pressure gauge!! Many car makers donot due to to smaller condenser but u new that !!
I guess u new all about the freezing temp that's why u mentioned it !! Many auto systems can operate around 30 psi on the low side very successfully .

Last edited by swampy 6x6; Jun 30th, 20 at 6:30 AM.
swampy 6x6 is offline  
post #20 of 20 (permalink) Old Jun 30th, 20, 9:02 AM
Gold Founding Member
Administrator
 
Join Date: Aug 1998
Location: near Kansas City
Posts: 62,783
Garage
Re: A/C questions, newer car

Tell me all about it.
LeoP likes this.

.
.
.
.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Dean is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome