Ac pressure for w210 1999 e300d - PeachParts Mercedes-Benz Forum

biopete · #1 03-30-2015, 04:16 PM

I can't find numbers in wiz or online. What shoul ultimate reading be on #7 of the acc unit data?

My system drained down and I put some charge in it. I want to see how fast it leaks so I'm not overfilling. Before it was 4 and ec light wouldn't go off. Now it is 14. I put a little oil charge in too. I hope not too much. I put about 1.5 oz oil

Thanks

biopete · #2 03-30-2015, 06:04 PM

No one knows what max reading 7 should be on the ac diag screen in the w210? I looked in wis and that thing is just stupid hard to find simple things sometimes

. Like I couldn't find an error code chart or even how to get the diag and read error codes and reset them.

TMAllison · #3 03-30-2015, 08:00 PM

Its a variable pressure system. Evacuate and refill for proper fill levels.

Search SteveBFL's name for the actual values and error codes descriptions in the AC system and how to retrieve both.

compu_85 · #4 03-30-2015, 09:38 PM

2x. With a variable displacement compressor you can't go by pressures like on the older cars.

-J

biopete · #5 03-30-2015, 11:04 PM

Thanks all. I'll go for that

VW1300 · #6 07-20-2015, 12:39 PM

Biopete, how did this issue turn out for you?

shertex · #7 07-20-2015, 12:53 PM

I know even less about variable displacement compressors than I do the older designs!

But, upon acquiring both my 98 and my 99, I found AC weak so I added 12 oz. or so of R134 until the low side pressure was where I thought it needed to be. If I'm understanding correctly, this method is no good. Can anyone elaborate? What is the risk?

treetops · #8 07-20-2015, 04:42 PM

I have read the risk is overcharge, but then again some say that cannot happen because the can psi is less than the max psi of the system. Not helpful I know. There is always a lively discussion on BW about this in the summer.

I have added R134 twice this summer, last time about 3 weeks ago. I guess I am overly cautious so dont add much but enough to bring the level up to about 13-14 when the AC is running on LO. Some say around 18 is the right number. HTH

97 SL320 · #9 07-20-2015, 05:30 PM

One quick check for " it isn't too low but no way to tell if overcharged " is to feel the outlet of the evaporator. If everything else is working properly, the tube should be cold. If it is warm / hot there isn't enough freon.

I recently recharged Moms 97 C280 and I "think" the tube was hot until the last 100 - 150 grams or so. Interior cooling was OK well before that, it got better when fully charged.

An overcharge will cause slugging, this is where liquid freon enters the compressor inlet. A compressor will pass liquid as they use reed valves but they are not designed to pump liquid very long.

shertex · #10 07-20-2015, 07:13 PM

Looks like I'm at 16 bar with 90F ambient. Good to know...I'll use that in the future instead of the gauge.

Is there a set of guidelines as to what it should be a different ambient temps?

shertex · #11 07-20-2015, 07:26 PM

For different car, but looks like useful info:

http://www.mbforum.it/wp-content/uploads/imported/2855.pdf

VW1300 · #12 07-20-2015, 09:24 PM

While we're on the subject of A/C - my left vents don't blow as cold as the rights. Two reasons for this, I've gathered, and they're not exclusive:

1. Low on refrigerant
2. Left duovalve stuck open

With the car running in the garage and the A/C on, I gathered the following codes. This was about an hour after I got home from work so the engine was still warm, and the ambient air was about 88F

1. inside temp 35C
2. outside temp 36C
3 L heat exchanger 23C
4 R heat exchanger 17C
5 Evap temp sensor 27C
6 ECT 86C
7 Refrigerant pressure 14 bars
8 refrigerant temp 52C

Does the left heat exchanger look significantly warm enough to conclude that the duovalve is stuck open? I tapped on it with a screwdriver but the temp didn't come down. The 14 bars of pressure seems OK to me at idle with the A/C on high, is that correct?

Thanks,

Charlie

treetops · #13 07-20-2015, 09:26 PM

In the BW stickies

Automatic Climate Control Diagnostic Trouble Code (DTC) Memory - Mercedes-Benz Forum

and

Steve Brothertons excellent how to on both ACC and DTC, which also includes an overview of the system which is very helpful and basically says take it to a pro.....

MERCEDES-BENZ: A/C Diagnostics & Evaporator Replacement

shertex · #14 07-20-2015, 09:28 PM

If the duovalve was stuck open, wouldn't you get hot air and not simply air that wasn't cold enough?

treetops · #15 07-20-2015, 09:30 PM

Quote:

Originally Posted by VW1300

While we're on the subject of A/C - my left vents don't blow as cold as the rights. Two reasons for this, I've gathered, and they're not exclusive:

1. Low on refrigerant
2. Left duovalve stuck open

I tapped on it with a screwdriver but the temp didn't come down. The 14 bars of pressure seems OK to me at idle with the A/C on high, is that correct?

Thanks,

Charlie

Bang it harder... and it should start to work.Sadly I am at the point where I have to get out and rap them about 20 times to get nice icy cold air. To boot, seems the 98-99 e300 duovalves are not really servicable as in other models

Time to find a replacement