Gain extra benefits by becoming a Supporting Member Click here find out how!
Classic Performance Products Classic Parts
Ciadella InteriorsAmerican Auto Wire Classic Industries
Chevs of the 40sDanchuk Catalog
Hellwig Products IncPerformance Rod & CustomEcklers AutoMotive
Nu-Relics Power Windows
Impala Bob's Bob's Chevy Trucks Bob's Chevelle Parts Bob's Classic Chevy



Username Post: A/C pressures        (Topic#346403)
gchemist 
Senior Chevytalk Moderator
Posts: 24269
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
08-04-17 04:40 PM - Post#2702843    

Does anyone know what a/c pressures are for an R4 compressor? I have hoses to check.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
gchemist 
Senior Chevytalk Moderator
Posts: 24269
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
08-15-17 09:01 AM - Post#2704310    
    In response to gchemist

~50 PSI low side
~250-300 PSI based on ambient temp.

The R4 is toast anyway. Time to upgrade SD508 style.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
toro455 
"3rd Year" Silver Supporting Member
Posts: 428
toro455
Loc: Western NY
Reg: 06-15-02
08-19-17 08:32 PM - Post#2704855    
    In response to gchemist

gchemist,
As you mentioned ambient will impact the high side pressure. As well how well the condenser performs will also impact what the high side pressure ends up being (includes condenser type and how good the airflow is). I don't know where your expansion device is but if it is possible to read the condenser out pressure before the expansion and as well measure the temperature in the same position you should be looking for a temperature which is sub cooled. So taking the pressure reading you could check the saturation temperature in a table and then see if the temperature which you read is colder. As you add refrigerant the sub cooling at the condenser exit will increase.

I didn't catch what type of vehicle you have but if it's a c/k truck the orifice might be in the condenser outlet or close to it. If that's the case you probably won't be able to measure pressure there but you may be able to roughly estimate the condenser out pressure by the inlet pressure. You would likely see about 10psi drop I suspect from inlet to outlet at idle; more if the high side port is closer to the compressor.



 
gchemist 
Senior Chevytalk Moderator
Posts: 24269
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
08-20-17 05:36 AM - Post#2704887    
    In response to toro455

toro455,
Thanks for replying. A/C systems are new to me. The system is my '95 GMC Jimmy. It's the same for a C1500. The orfice tube is about <6-8" from its high pressure port. I'll go into more detail on my other thread about it.

Will a hand held laser thermometer work? I've been looking for an excuse to buy one.
I went all out and upgraded to an SD7HD. The SD508 were not specially made for R134. The SD7HD is specific for R134. Only the condenser is original (R134 type). Compressor, lines, evaporator, and tube are all new.

How long is a good vacuum? A new pump pulled it past 60 in hg fast. Reading was between 60 and 76 hg. We pumped it about 20 min or so.

Once I figure out the electrical wiring, I'll use my gauges that read it "in".

Attachment: SD7HD.jpg (103.92 KB) 12 View(s)


Sanden SD7HD replacing an R4.


'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


Edited by gchemist on 08-21-17 04:40 AM. Reason for edit: No reason given.

 
toro455 
"3rd Year" Silver Supporting Member
Posts: 428
toro455
Loc: Western NY
Reg: 06-15-02
08-20-17 08:35 PM - Post#2704990    
    In response to gchemist

Yes one of the hand held should be ok but it needs to be accurate in the range you are looking for. The risk with an off brand is accuracy. They do actual sell the infrared with a place to plug in a thermocouple as well. I have the Fluke 561 HVAC Pro Infrared Thermometer and it does have this option.

Your vacuum numbers don't seem correct. It's not possible to pull a perfect vacuum and your reading is about double that. I don't really know how long the vacuum should be held but it seems like 20-30minutes would be enough; longer won't hurt anything. You ideally want to boil off any refrigerant and moisture but the desiccant used with R134a chemically locks the moisture from my understanding so to release it from the desiccant takes extreme heat.



 
gchemist 
Senior Chevytalk Moderator
Posts: 24269
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
08-21-17 04:39 AM - Post#2705033    
    In response to toro455

We used my friends gauges. They are R12 hoses with multiple scales on it. I was probably reading it incorrectly. As soon as I find the electrical problem on why the compressor will not turn on, I'll use my new gauges to read pressure. It reads in PSI. My local shop moved the R4 high pressure switch to the exit hose point. I'm almost sure the high pressure switch is not sending voltage through the harness to the compressor.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
Icon Legend Permissions Topic Options
Report Post

Quote Post

Quick Reply

Print Topic

Email Topic

666 Views
FusionBB
FusionBB™ Version 2.1
©2003-2006 InteractivePHP, Inc.
Execution time: 0.217 seconds.   Total Queries: 14   Zlib Compression is on.
All times are (GMT -0800) Pacific. Current time is 11:39 AM
Top