W124 500E A/C efficiency ?

[ke6dcj]

Summer heat and humidity is among us in Florida.

As such, my wife has noticed that the 500E's A/C doesn't get very cool, esp. compared to the wagon's converted R134a system (new compressor, condenser, dryer, and expansion valve 3-years ago).

A couple of days ago it was about 97-F, and 83% humidity, for a heat index of about 103-F.

After driving 45-minutes on the freeway, the coolest the center vent could get was about 57-F.

FWIW, my mechanic said there was no bubbles in the A/C's sight-glass, and 6-months ago he replaced the expansion valve, drew a vacuum overnight, and recharged it fully.

Is this normal for a 500E in this weather condition ?

I know the M119 engine produces a lot more heat than my M104 AMG . . .

:-( neil
1993 500E

If there are no bubbles in the sight glass, the problem is most likely either a heater valve that is dribbling a little coolant through to the heater core or a bad vacuum pod on the fresh air door.

The heater valve is controlled by the pushbutton unit and when I have seen it fail, it doesn't just warm up a little, it warms up ALOT!

Pull the glove box and apply vacuum to the top two lines on the switchover valve that is just in front of and below the glove box. If either one of those lines leak, then you will have to replace the vacuum pods that are in front of the heater core. This will require dash removal. When replacing them, replace the rubber elbows as well. You don't want to do this job a second time because of a fifty cent part.

Good luck,

[jcyuhn]

The 93 has a passenger airbag rather than a glovebox. I've never looked up the procedure to remove it, but other than that the process to check the vacuum elements should be the same as for earlier cars. I'm going to double up on Larry's bet - probably a problem with the recirculate flap. It's likely you're cooling/dehumidifying only outside air. Works much better with 100% recirculated air - once all the moisture is out, it gets real cool...

Pull the airbag, then check all seven vacuum lines on the switchover valve. All should hold vacuum. Let us know which ones are leaking, and we'll let you know how much work you're looking at.

- JimY

[400E]

Just as a point of data from another M119 owner (albeit a measly 400E), I've never been really happy about my car's cooling ability in stop-and-go traffic, despite having a completely functional (now) aux fan system and the Stu Ritter constantly-engaged engine fan.

However, once on the freeway, I get plenty of cold air. Even in mid-90 temps with high humidity, 5-10 min on the interstate and my cabin fan is able to slow down and the cabin is quite comfortable. Soon as I hit my exit ramp and get into traffic, though, it's back to just-barely cool enough.

Have you checked to make sure your condenser is free of bugs, etc.? Airflow up front seems to be a major issue for these vehicles.