Weak a/c--are these pressures OK?
 

I have searched and read numerous posts, and I'm still confused.

Tested my a/c today, and got the following readings:

'98 ML320
static pressure: 110
ambient temp: 80 (rose to over 90 during test)
RH: 65%
idle: 45 lo, 220-240 high
2000 rpm: 30/170

after the pusher fans kicked in and stayed on constantly: 40/200 at idle

center vent temp, fan on high, recirc off: 62
vent temp, cruising 40-60 mph: 55
vent temp, accelerating: 52

Usually takes a long time to cool this vehicle off; do these pressures indicate an undercharged condition? In another post I found that the ML320 holds less refrigerant than my Golf; I wonder if that's why the Golf's a/c works better.

Those are good readings...but how good is strictly dependant on the ambient temp & humity...Since the system is 8-9 years, try a evacuation & recharge.

Ambient temp & humidity are listed above. I will clean all the bugs out of the condenser, then evacuate & recharge if that doesn't have enough effect.

BTW I should mention we've had this car for 6 years, and the a/c has always been underpowered. This is not really a new problem.

I have no specific measurements as you do, Lenny, but I do, or did, have three other vehicles to compare our '00 ML320 to - a '99 Camry (sold this past winter), an '03 Camry and a '78 300SD. We bought the 320 new, as with the two Camry's, and have known the 300SD since new and owned it since 1985. Since new we have thought the ML's air conditioning was weak, as we also felt about our first ML, a '98 320. The air vent temperature was noticably higher than our other vehicles and we have to run the ML fan at a higher speed for the A/C to keep up. Even the '78 A/C, which had been recharged once in the late '80's, is more adept. The issue with the A/C is not all that unlike the issue with the driver side footwell being so cold in the winter. Maybe it is an air distribution problem.

As a side note, the climate control in the 300SD is the best heater and A/C system we have had compared to our many other vehicles we've owned. When we set the dial at 72 degrees the interior stays within a small comfort range whether heating or cooling - very nice.

We are currently using the 320 on a long trip with tempertures in the 90's, moderate humidity, and the A/C is doing ok. However I feel this is one of the areas that could have been improved on in this vehicle.

Jim W.

AFAIK, the weak A/C was addressed in the MY02 facelift when they added another compressor for the rear vents...

One of the issues w/ the original ones is the coolant tubing under the hood isn't insulated, so that may have affected how well it worked :-P

We have an 03 ML500 and the a/c is outstanding. Sitting in the sun at the Colorado River near Parker AZ with the temp. over 120 F it takes very little time to cool off the truck. Much better than any other vehicle we have owned.

Bob