A/C slow to cool - PeachParts Mercedes-Benz Forum

dragon · #1 06-08-2003, 05:01 PM

Hello:
I am new to the forum so bear with me.
I have a 95 E420 and live in Phoenix Arizona, outside temps are 100+now but we use the A/C most all year.
My problem is that the A/C takes a very long time (16+ mins) before it starts to blow cold air. I didn't have this problem last year so it is something new. Had the a/c checked and the mechanic said I needed to flush the cooling system? This didn't seem logical so I am posting my question here. Any suggestions?
Thanks

stevebfl · #2 06-08-2003, 06:23 PM

Yes, it doesn't seem logical. What is the point? Sounds like something to do while hoping it will work better.

Larry Delor · #3 06-09-2003, 09:14 AM

OK...this is PURELY a GUESS....ok?

I am guessing that your low speed aux. fan isnt coming on. The reason that you are finally getting air after 16 minutes, is because the engine temp finally reached the point to where the high speed electric fan comes on, and is providing some relief to the a/c condenser at the same time.

Something you can do in the meantime.... While the A/C is turned on, check to see if the cooling fan is coming on, and check the sight glass on the dryer (might need to use a cotton swab to clean it first) and see if you see anything flowing through there...lots of bubbles is usually a bad thing. Once you have done that, come back here, and report your findings and/or do a search on A/C problems, and do some research.

Good luck...and keep your cool

Mike Richards · #4 06-09-2003, 01:57 PM

Does this 134A equipped car have a sight glass in the receiver-dryer?

Even if it does, tech manuals state that this is not a reliable technique for 134A systems. Have ANOTHER tech hook up some 134A gauges for starters and see what the system charge looks like.

400E · #5 06-09-2003, 08:30 PM

The aux fan theory is interesting and worth checking out. However, in my experience it should still cool OK as long as the car is moving (and thus you get ram air over the condensor). On the other hand, if it doesn't cool when in stop-and-go traffic but then cools off nicely once you start moving again, that would point to a possible aux fan problem.

Another simple idea. When cabin temp is a lot higher than set point, like when your car is sitting closed up in 100 degree heat, the system will call for recirculated air. Obviously, if the air in your car is 120 degrees to start with, even if your AC, aux fans, etc. are working perfectly, the output air will still only be about 30 degrees cooler (in this case, 90 degrees) and thus feel warm.

Does it help if you open all the windows for the first mile or two to get rid of the superheated air inside?

dragon · #6 06-10-2003, 12:33 AM

OK
Thanks for all the suggestions. I will try them all in the next day or so and see what happens and let you know the results

haasman · #7 06-10-2003, 01:19 AM

I agree, the coolant has nothing to do with initial cooling via the AC.

When was the last time the AC was serviced? Have you had it checked for leaks? You can have a fluorescent dye introduced to the system that enables a tech to easily find a leak.

Is your engine belt tight? Any squealing recently?

Also vaccum the temperature sensor which is in the interior light/sunroof switch cluster up above. I did this on a 300SD and it made a big difference in cooling.

Also, there is a tube that connects to a small fan which pulls air through this sensor, it could be your fan is no longer working or the tube has rotted away.

The system also allows outside air into the cabin via a blending. Sometimes these "doors" or their actuators fail allowing too much air into the cabin.

Per the previous suggestion, have you tried using the recirculation only to see if the cooling improves?

Keep us posted,

Haasman