Mercedes-Benz Forum banner

1 - 11 of 11 Posts

·
Registered
2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
Joined
·
5,447 Posts
Discussion Starter #1
Haven't used my A/C in about a month since it has cooled off...
Turned it on today and all I am getting is hot air. Clutch is engaging fine, but I hear a bad noise that goes away when I switch off the A/C.

What do you guys think?
Weird thing is that I can hear pressurization coming from the evap...just no cold air at all.

Compressor when I removed it to replace my evaporator was replaced sometime around 1997...It looked okay though. Just flushed it with mineral spirits to remove any leftover R134a oil and put correct R12 oil back in.

One thing after another :crybaby2:
 

·
Premium Member
99 SLK230 Kompressor, 5 Speed Manual
Joined
·
1,117 Posts
Start by checking the pressures. Since the clutch is engaging, we know it's not completely empty, but it still could be low enough to prevent cooling. I wouldn't get too worried about the noise just yet.

Also if the recirc pod is not working if the ambient is high, it could prevent cooling. Also if too much coolant is making it past the heater valve it could prevent cooling. Don't condemn the compressor just yet. We can work through it until we find what is indeed wrong.

Hope this helps.
 

·
Registered
1993 300E, 2003 996 Turbo X50
Joined
·
624 Posts
Sounds like the same symptoms mine had when it died a few months ago. Also the use of 134a in your system almost assured that, the oils are not compatible. Did someone manage to charge your R12 system with R134a?
 

·
Registered
2000 SL500
Joined
·
193 Posts
R12 oil and PAG oils do not mix. Did you also replace your metering device when swapping? If switching from r-12 to R134a, or the opposite, all components should be replaced (metering device, compressor, and accumulator). Evap shouldn't need replacing though.
 

·
Premium Member
99 SLK230 Kompressor, 5 Speed Manual
Joined
·
1,117 Posts
The way I understood the OP, he flushed the system, added an R12 compatible oil and recharged with R12 at the time of his compressor change. I have reversed converted several systems back to R12 doing this and it works out fine.

The need to replace all these components when changing refrigerants is unnecessary. The filter/drier should certainly be changed and if a parallel flow condensor is being used, they are near impossible to completely flush. Other than that a thorough flush will allow you to go to the refrigerant and compatible oil of your choice. I hope the refrigerant choice is a good one though.

A noteworthy issue in this thread is that you should never flush a compressor with solvent. Simply turn the compressor to get as much oil out as possible and then run some of the new oil in and through the compressor. You can get by with flushing with solvent sometimes, but it's not at all good for the compressor.
 

·
Registered
1987 USA 300E 155K+ miles 3.0L I6 Single Overhead Cam
Joined
·
59 Posts
Did you evac it after you opened the line? Otherwise the free-on will not work if there is air in the lines. Do you hear your clutch engage and disengage a lot when you have the A/C on? And also, if it was replace around 97 it might of been converted to R-134a to meet regulations. R-134a and r-12 fittings are different so you would know.
 

·
Registered
2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
Joined
·
5,447 Posts
Discussion Starter #7
Car came to me changed to r134a from the dealer at some point...sticker's ink was rubbed off.

I evac'd system, flushed all lines, replaced drier + evaportor...flushed condensor. The whole 9 yards. I did everything to the book. I did flush the compressor with mineral spirits only because I read it could be done and I ensured I put the new oil in and let it drain out completely a number of times. A final evac drew -80PSI (IIRC) before the R12 was put in. 2.2lbs IIRC again.

It was working great before.

Only reason I think something mechanically is wrong is because with the A/C on, I always notice it is slower and it is drawing some HP away. Clutch engaging now, there is no decrease in power. That's the reason why I think there is a mechanical issue.

I'll try and get my gauges on soon....having back issues right now so I'm almost out of action :(
 

·
Registered
1987 USA 300E 155K+ miles 3.0L I6 Single Overhead Cam
Joined
·
59 Posts
Sorry to hear about your back. Just a thought, maybe if you over charged the system it would cause the compressor to not do its job right, (or making it hard on it) causing the power draw from your engine and thats where the noise could be created? I don't want to lead you the wrong direction though. Also, maybe there is a clog or a Kenk in one of the lines.
 

·
Registered
2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
Joined
·
5,447 Posts
Discussion Starter #9
It's finally warmed up to a reasonable temperature now. 78F outside today
Something is definitely wrong...

Static



A/C On -- Clutch Engaged (vent temps are not cold. A/C not functioning



There seems to be no pressure at all on the low side :confused:
As soon as I turn the A/C off, high+low return to static pressures.
 

·
Registered
2000 SL500
Joined
·
193 Posts
Does the high-side have the proper pressure?

If the low-side is low and the high-side is normal to SLIGHTLY low, the problems could be: a restriction in the low-side, moisture in the system, or a defective thermostat.

If the low-side is low or VERY low and the high-side is low, the problems could be: clogged metering device (orifice tube or thermostatic expansion valve "TXV") inlet screen, defective valve or tube, moisture in the system, or a high-side restriction.

Straight out of my Automotive Heating and A/C book from last semester, lol.
 

·
Registered
2008 E350 4M, 2016 Audi Allroad, 2019 Audi Q5
Joined
·
5,447 Posts
Discussion Starter #11 (Edited)
I'm not sure. It "looks" to me like its low on refrigerant, but I wanted to confirm that this does not show any other issues.

Everything in the system is brand new minus the compressor and condenser. All lines were flushed, new receiver/drier, expansion valve + evaporator. Unless the compressor has nuked itself, I see no reason for any blockages.
 
1 - 11 of 11 Posts
Top