a/c issues where should i start??? - PeachParts Mercedes-Benz Forum

richclan · #1 05-31-2011, 06:38 PM

i have owned this car for 4 years and the a/c has been very good until this year. i would say it blows at 70 - 75 deg now at center vent.

the ac clutch engages with no issues

lots of bubbles in the sight glass

i looked at the lines and dont see any oily connections, high pressure lines are blue

aux fan runs good even before i start it up

factory r12 charge i believe, because the car has less than 60K on it.

i dont want to convert it after reading many posts on the subject.

thanks

vstech · #2 05-31-2011, 07:31 PM

start with a set of gauges and measure the pressures at operating temp.
also, check to see if the aux fan is operating.
also check the condition of the front coil for damage and clean it.
once this is done, go online and take the open book 608 test, then go to napa and get some R12.

richclan · #3 06-01-2011, 10:31 AM

ill have to ask around for the gauges i dont have any

some threads stated that i could add r12 until the bubbles disappear in the sight glass

and if i used the freeze 12 instead of r12 whats the story on that stuff???

oh and its the 609 test for cars

thanks

vstech · #4 06-01-2011, 10:41 AM

adding R12 without knowing your pressures is not wise.
best to get readings first.
if you just want to ad 12 in until the bubbles go away, you should THOROUGHLY clean the condenser, and verify the aux fan is working properly, and set a large blower in front of the car prior to checking for bubbles.

richclan · #5 06-01-2011, 11:04 AM

aux fan is good to go and the condenser is very clean, see right through it and the radiator

also am i missing anything else to test???

richclan · #6 06-03-2011, 01:27 PM

forgot to ask what pressures are needed on the high and low sides.

i was lucky to find a friend with gauges and some old r12 freon

vstech · #7 06-06-2011, 05:52 PM

Quote:

Originally Posted by richclan

aux fan is good to go and the condenser is very clean, see right through it and the radiator

also am i missing anything else to test???

the ability of light to pass through a coil does not insure the coil's ability to transfer heat.
I said CLEAN the coil.

leathermang · #8 06-03-2011, 01:31 PM

The FSM warns about using the sight gauge to fill refrigerant...
there is a possibility of it indicating need for more refrigerant when it is already full... few things worse for an AC than having too much refrigerant since CHANGING from one phase to another is the basis of the physics... so a proper differential in pressure needs to exist... that is taken away by too much refrigerant...
Fill by pressure and vent temperatures...or .. if a new fill... but accurate weighing of the refrigerant.

richclan · #9 06-03-2011, 02:07 PM

Quote:

Originally Posted by leathermang

The FSM warns about using the sight gauge to fill refrigerant...
there is a possibility of it indicating need for more refrigerant when it is already full... few things worse for an AC than having too much refrigerant since CHANGING from one phase to another is the basis of the physics... so a proper differential in pressure needs to exist... that is taken away by too much refrigerant...
Fill by pressure and vent temperatures...or .. if a new fill... but accurate weighing of the refrigerant.

do you know what pressures are needed for the high and low