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  #1  
Old 03-21-2012, 04:39 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 4,998
420SEL AC Pressures

Hey everyone,

With this recent warm up, I've decided to go through the cars and check AC systems. Much to my surprise my 190E's works, in the past it had leaked out and stopped working. However my 420SEL's is not working so well.

The compressor kicks on, I put the manifold on it and got 60 PSI static pressure, with engine on readings with the aux fan on and ambient temp at front of radiator about 80F:

According to charts at 80F ambient one should see ~18 Low, 170-210 High.

I saw,

At Idle:
3 Psi Low, 100 Psi High

At 1500 RPM:
0 Psi Low, 100 Psi High

So I felt that the charge was low, so I grabbed a can of R12 and started charging.

Idle:
20 low, 165 High

1500:
10 low, 165 High

I checked the gauge I put in the center vents, it was hitting high 60s. So I thought it was still undercharged a bit. I think I overcharged a bit, I ended up with:

Idle:
30 low, 175 High

1500:
17 Low, 180 High

That's a question I have about these charts are these pressures at idle or at a higher rpm?

What do you guys think?


EDIT: After a short trip (~40mph speed) I achieved about 55F at the center vents with my cheapo dial thermometer.
EDIT: Did another run on the freeway, used my DMM with temp sensor, lowest was 56F. Sat between 56-58F.
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82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

Last edited by JamesDean; 03-21-2012 at 05:24 PM.
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  #2  
Old 03-21-2012, 06:30 PM
JamesDean's Avatar
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Quote:
Originally Posted by ps2cho View Post
I am no expert, but it looks good.

Any idea where it was leaking out from? Hopefully not the evaporator...
Not a clue. I'd have to get some dye and put it in there and to find out. The compressor is relatively new, we had it replaced 2 years ago. So I'd hope the o-rings engine side were all replaced.

I ran my 190E and its AC is substantially better. I got 34F at the center vents with the fan on low. The 420SEL only was able to muster 58F under the same conditions.

The 190E is running ES-12A whereas the 420SEL has R12.
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Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #3  
Old 03-21-2012, 07:06 PM
compu_85's Avatar
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How does the sight glass look? From what I recall in the FSM the pressures should be higher on an 80* day.

EDIT: nevermind, according to this it sounds like you have it about perfect.



-J
Attached Thumbnails
420SEL AC Pressures-w126-110-acpressure.jpg  
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1991 350SDL. 230,000 miles (new motor @ 150,000).

2013 Fiat 500E. 20,000 miles, 80 miles at a time.
2012 Passat TDI. 95,000 miles. More space, power, and fuel economy than the Benz
2004 Touareg V10 TDI. 150,000 miles. One of 450.
1999 Jetta TDI. 310,000 miles.
1992 Jetta ECOdiesel. 156,000 miles. 1 of 48. Sold.
1991 Jetta ECOdiesel. 430,000 miles. 1 of 700. Sold to VeeDubTDI, totaled in front of our house

Last edited by compu_85; 03-21-2012 at 07:17 PM.
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  #4  
Old 03-21-2012, 07:16 PM
JamesDean's Avatar
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Quote:
Originally Posted by compu_85 View Post
How does the sight glass look? From what I recall in the FSM the pressures should be higher on an 80* day.

-J
I'll have to take a look at the glass.

Are you talking about the low side ? high side? at idle? at 1500?
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #5  
Old 03-21-2012, 07:17 PM
compu_85's Avatar
Waiting for his Model 3..
 
Join Date: May 2008
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Posts: 5,166
See my edited post. I thought the low and high side both seemed low at 1500 RPM.
__________________
1991 350SDL. 230,000 miles (new motor @ 150,000).

2013 Fiat 500E. 20,000 miles, 80 miles at a time.
2012 Passat TDI. 95,000 miles. More space, power, and fuel economy than the Benz
2004 Touareg V10 TDI. 150,000 miles. One of 450.
1999 Jetta TDI. 310,000 miles.
1992 Jetta ECOdiesel. 156,000 miles. 1 of 48. Sold.
1991 Jetta ECOdiesel. 430,000 miles. 1 of 700. Sold to VeeDubTDI, totaled in front of our house
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  #6  
Old 03-21-2012, 07:20 PM
JamesDean's Avatar
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Quote:
Originally Posted by compu_85 View Post
See my edited post. I thought the low and high side both seemed low at 1500 RPM.
So perhaps its still undercharged?
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #7  
Old 03-21-2012, 07:30 PM
compu_85's Avatar
Waiting for his Model 3..
 
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Location: Springfield VA
Posts: 5,166
With R12 you should be able to look at the sight glass. There should be few to no bubbles.

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

2013 Fiat 500E. 20,000 miles, 80 miles at a time.
2012 Passat TDI. 95,000 miles. More space, power, and fuel economy than the Benz
2004 Touareg V10 TDI. 150,000 miles. One of 450.
1999 Jetta TDI. 310,000 miles.
1992 Jetta ECOdiesel. 156,000 miles. 1 of 48. Sold.
1991 Jetta ECOdiesel. 430,000 miles. 1 of 700. Sold to VeeDubTDI, totaled in front of our house
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  #8  
Old 03-21-2012, 09:47 PM
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Location: Louisiana266 Maloy Rd winnfield71483
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Make sure you do not have a vacuum proublem with one of the controle units for the fresh air and heater door, I had that trouble with my wifes 420 sel and could not cool the car very well. JNT
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  #9  
Old 03-21-2012, 09:48 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
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Quote:
Originally Posted by compu_85 View Post
With R12 you should be able to look at the sight glass. There should be few to no bubbles.

-J
I looked at the sight glass, I saw white stuff rolling around in there, didnt really see any bubbles though. Just white stuff.
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #10  
Old 03-21-2012, 09:49 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 4,998
Quote:
Originally Posted by just-n-time View Post
Make sure you do not have a vacuum proublem with one of the controle units for the fresh air and heater door, I had that trouble with my wifes 420 sel and could not cool the car very well. JNT
Hmm. I havent checked into any of that yet but I think the re-circulation isnt functioning properly. At least I cannot hear it engage. In the 190E its very obvious.
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #11  
Old 03-22-2012, 10:57 AM
just-n-time's Avatar
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Location: Louisiana266 Maloy Rd winnfield71483
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sight glass(white stuff)

Quote:
Originally Posted by JamesDean View Post
I looked at the sight glass, I saw white stuff rolling around in there, didnt really see any bubbles though. Just white stuff.
that white stuff is air swirling around if you put more in and look at the glass you will sea it dissapate you shoul have just an ocational buble.
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  #12  
Old 03-22-2012, 11:03 AM
compu_85's Avatar
Waiting for his Model 3..
 
Join Date: May 2008
Location: Springfield VA
Posts: 5,166
Ya, white foam = bubbles.

While you're doing your test you should use a hose to wet the condenser.

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

2013 Fiat 500E. 20,000 miles, 80 miles at a time.
2012 Passat TDI. 95,000 miles. More space, power, and fuel economy than the Benz
2004 Touareg V10 TDI. 150,000 miles. One of 450.
1999 Jetta TDI. 310,000 miles.
1992 Jetta ECOdiesel. 156,000 miles. 1 of 48. Sold.
1991 Jetta ECOdiesel. 430,000 miles. 1 of 700. Sold to VeeDubTDI, totaled in front of our house
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  #13  
Old 03-22-2012, 05:08 PM
JamesDean's Avatar
Electrical Engineer
 
Join Date: Apr 2005
Location: NE Ohio
Posts: 4,998
Hmm so you're saying I should put more R12 in the system and observe the sight glass while I'm doing so?

Based on that chart I get:

Outside Temp 80F = 26.6C
2 Bar Low = 29 PSI Low
22 Bar High = 319 Psi High

That high side seems...high.
__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

82 300SD 145k
82 300SD 265k
87 420SEL 230k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k
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  #14  
Old 03-22-2012, 09:01 PM
just-n-time's Avatar
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Join Date: Feb 2006
Location: Louisiana266 Maloy Rd winnfield71483
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Quote:
Originally Posted by JamesDean View Post
Hmm so you're saying I should put more R12 in the system and observe the sight glass while I'm doing so?

Based on that chart I get:

Outside Temp 80F = 26.6C
2 Bar Low = 29 PSI Low
22 Bar High = 319 Psi High

That high side seems...high.
Ok lets see if I can help you on this, the first thing I think of is a restriction to flow if I get higher than normal reading on the high side, But first I have to no if the system is over charged. This is when I bring the sight glass into play as I charge the system I look for very slow or even no movement in the glass, of course it is moving along at its normal flow rate but as the airated bubles go away it looks like things are standing still. Now high pressure could also come from contaminated freon, water the dryer, may be in need of replacement. I hope I have helped you a little, I know you have given me great info. By the way I converted all of our units to freez12 it has propane in it and not every one carries it but it sure is cheaper than the old 12. JNT
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  #15  
Old 03-23-2012, 12:34 AM
Hit Man X's Avatar
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Thumbs up

http://www.ackits.com/aacf/ptchart.cfm

Test these at high idle.

Make sure you have no bad vac pods, a dead center pod keeps the defroster pod from fully closing which shuts the center vent flapper door...

Freeze 12 sucks in these cars in the city. Works fine freeway. Cost of R12 is not bad at all if you look hard and buy it off season.
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I'm not a doctor, but I'll have a look.

'85 300SD 243k
'87 300SDL 251k
'90 300SEL 322k
'91 560SEL 183k

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