Ac 50f. - Mercedes-Benz Forum
 
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post #1 of 10 (permalink) Old 05-20-2019, 08:53 AM Thread Starter
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Ac 50f.

Hi folks. Itís that time of the year.

82 F outside. Ac in my 420 set at 70 in auto mode only gets down to 50f.
96 jag I just drove blows 40f.

I remember last year my 420 was struggling a bit. Especially when parked. It was better once we got moving.

Should I be worried ? Have the Freon checked ?

Both fans turn. And while it feels comfortable now, I donít want to be uncomfortable when temps reach 90s.

Much thanks!

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post #2 of 10 (permalink) Old 05-20-2019, 11:11 AM Thread Starter
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Ac 50f.

Got down to 45f from ac vents after a 10 minute drive at medium speeds.
Outside temp 88.

Are these systems really this lazy to come alive ?


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post #3 of 10 (permalink) Old 05-20-2019, 02:51 PM
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If tip top they produce a wall of cold quickly, but there's loads of stuff that can make it be lazy. Type of gas, too little or too much pressure, blocked fins, etc.

There's an element of dialling in the gas pressure if it's a converted system using R134. Once right it can be good but it can take a bit of 'tuning' by altering the amount of gas. The unconverted systems are awesome, my SEC is not yet R134 and it's a very rapid wall of very cold air.

My converted SE had a new compressor and was a bit meh after that. AC guy got it dialled in last year and its great now but it took a bit of experimenting with the gas pressure.

In an ideal world you would just need a slight top up. Its weak for some reason and at idle is where it shows.

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post #4 of 10 (permalink) Old 05-20-2019, 03:37 PM Thread Starter
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Quote:
Originally Posted by ianrandom View Post
If tip top they produce a wall of cold quickly, but there's loads of stuff that can make it be lazy. Type of gas, too little or too much pressure, blocked fins, etc.

There's an element of dialling in the gas pressure if it's a converted system using R134. Once right it can be good but it can take a bit of 'tuning' by altering the amount of gas. The unconverted systems are awesome, my SEC is not yet R134 and it's a very rapid wall of very cold air.

My converted SE had a new compressor and was a bit meh after that. AC guy got it dialled in last year and its great now but it took a bit of experimenting with the gas pressure.

In an ideal world you would just need a slight top up. Its weak for some reason and at idle is where it shows.


Well written my friend.

I think a. It if Freon wouldnít hurt. Last time I tried to add some the valve kept spraying Freon after I took the line off. Interesting times.

Iíll take it to a shop at sometime soon. See if they can add some gas.

Damn the 134. And who ever converted to it in my car .


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post #5 of 10 (permalink) Old 05-20-2019, 11:43 PM
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Last year I refreshed my AC with the "recommended on this forum" Enviro-safe replacement gas/system. My DD is W124 300TD estate which at some point in time converted to R134 but was low on gas and wouldn't activate the system pressure switch. I loaded the system with their StopLeak, compressor oil and about 2 1/2 cans of ES gas. System worked great last summer and continues to blow cold although I haven't put a thermometer in the vents this year (Seattle climate). Total kit was about $50 and well worth the time and investment. A couple other members have mentioned they are on 2-3 years with this system. I am a believer and was totally amazed that my 32 year old converted system on the highway was blowing out 44 degrees F with outside temp at 90 F. Mike
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post #6 of 10 (permalink) Old 05-21-2019, 01:33 AM
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Ive noticed on a few older mb they will not blow coldest until the car is moving at decent speeds . So you need to measure temps at speed , not while idling in park . If it’s cold while moving and just goes up to 50 at a stand still that’s fine .
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post #7 of 10 (permalink) Old 05-21-2019, 08:40 AM Thread Starter
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Quote:
Originally Posted by tusabes View Post
Ive noticed on a few older mb they will not blow coldest until the car is moving at decent speeds . So you need to measure temps at speed , not while idling in park . If itís cold while moving and just goes up to 50 at a stand still thatís fine .


This is basically whatís happening.

Thanks. Iíll have the pressure
Checked.


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post #8 of 10 (permalink) Old 05-21-2019, 09:59 AM
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when I purchased my 1991 SEL, I already was aware that there was refrigerant leaking from the compressor. I factored a new compressor into my purchase price offer. However, was pleasantly surprised on our first hot day when I turned on the AC, and low and behold, NICE cold air. At standing and while moving. It had been converted to R134 at some point. I checked the level and it was within the green mark on the guage I used. Seems to be a slow leak. For this year, I'll top up if/when needed, and maybe replace the compressor next year.

Also, local shop (owned by a friend) said theyve converted several old cars for customers by simply evacuating the r12 fully, and refilling with R134. Said it's worked perfectly fine in several long time customers older cars(not W126's though) . No changing out compressors/driers/other parts during the switchover.
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post #9 of 10 (permalink) Old 05-21-2019, 10:15 AM
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Quote:
Originally Posted by tusabes View Post
you need to measure temps at speed , not while idling in park.
True, in fact some car manufacturers give you the Lo/Hi pressures at 2000 RPM, which appears to be the "golden standard".

Although the system was not fully charged and outside were only 74-75 F, these are the pressures I noticed at idle (first picture) and at 2000 RPM (second). More important for this discussion is to notice the pressure differences. The gas is ES-12a.
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post #10 of 10 (permalink) Old 05-21-2019, 12:54 PM
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Quote:
Originally Posted by lesguy View Post
when I purchased my 1991 SEL, I already was aware that there was refrigerant leaking from the compressor. I factored a new compressor into my purchase price offer. However, was pleasantly surprised on our first hot day when I turned on the AC, and low and behold, NICE cold air. At standing and while moving. It had been converted to R134 at some point. I checked the level and it was within the green mark on the guage I used. Seems to be a slow leak. For this year, I'll top up if/when needed, and maybe replace the compressor next year.

Also, local shop (owned by a friend) said theyve converted several old cars for customers by simply evacuating the r12 fully, and refilling with R134. Said it's worked perfectly fine in several long time customers older cars(not W126's though) . No changing out compressors/driers/other parts during the switchover.
My '87 560SEL had a "compressor leak" that turned out to merely be two o-rings in the lump on top of the compressor to which the big refrigerant lines connect. DIY repair.

R12 requires Ester oil and R134 requires PAG oil. Be careful out there.
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