As for specifics, I can't tell you. But, if the value for #7 hits 30, the compressor kicks off and it will go back on when it lowers. As soon as it hits 30, it'll kick off.

Been there, done that. I topped of my system a few years ago and this occurred. Nothing like a ballpoint pen to relieve some pressure on the low side when in a pinch...

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#dieselFLEET
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'97 E300
'99 E300

I believe that I went into the specifics. Specifically, the value read at #7 can be dangerously wrong if there is a restriction prior to the sensor. In fact, there is a DTB for my car for this very issue. See the attachment.

While this does not apply to your later car, it is possible to plug the drier even if it contains no fault. Too much water in the system can do this, as can using sealers.

I infer that my drier is plugged from several pieces of information. First, the value at #7 is very, very wrong. Second, both values at #7 and #8 go DOWN upon compressor engagement. Third, the line coming from the dryer is cold to the touch. It should be hot.

Don't worry, I'm getting it fixed. But note that with the fault that I have now, there is absolutely no cutout for high head pressure. I believe that I have been venting refrigerant because of this, since no leaks in the system are apparent. I haven't checked the evaporator except by sniffing the vents, but tomorrow it is going on a lift to sniff the drain tubes.

Attached Files

38562_dtb_dtb_08_96-5_mbn_202.pdf (17.9 KB, 187 views)

I got my AC gauges.

Two questions:
-what pressures should I be watching for?
-I still can't find the "high side" port. Where is it exactly?

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Jake
1999 e300d PlantDrive WVO/SVO conversion
**note to self: oil changed at 268k kms**
1990 Toyota 4Runner FrankenDiesel swap

It's at the upper left corner of the condenser. Remove the cover over the auxiliary fan, then remove the small plastic door at the top left of the fan shroud.

As for the pressures, the chart is in the FSM and I don't have that with me just now.

anyone have a set of charts handy for the high & low side pressure I should be watching for?

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Jake
1999 e300d PlantDrive WVO/SVO conversion
**note to self: oil changed at 268k kms**
1990 Toyota 4Runner FrankenDiesel swap

Update and questions:

The "EC" light is on all the time now

I added ~8oz of r134a two days ago, but the compressor never kicked in.

Worried I had done something wrong, I took it to an AC shop this AM to have him check it out. He decided to start from scratch... vacuumed the system out, added oil & 2.2 lbs of r13a.

He had to run a jump wire to the compressor to get it to kick in, at which point the AC blew cold, everything seemed to be working fine as long as teh compressor was jumped.

However, the EC light stayed on, and even after being topped up the compressor won't kick in. He explained that he's had a few MBs that have to have their codes reset if the pressure gets too low.

Does that make sense? Are these codes that will clear themselves on their own after a few cycles? Do I need to bring it to a dealer to get teh codes cleared?

Any help is greatly appreciated!

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Jake
1999 e300d PlantDrive WVO/SVO conversion
**note to self: oil changed at 268k kms**
1990 Toyota 4Runner FrankenDiesel swap

If you have the pushbutton control unit N22, you can extract and clear the codes from there. A search should bring some results.

There is a common issue with the evap temp sensor failing that causes the EC light to stay on. I haven't read your entire thread but you can check the reading from the sensor and if it is whacko then have it replaced. It is a cheap part and takes 10 minutes or less to install.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Update:

Cleared the AC codes using MattL's advice from another thread:

Started the car and got beautiful cold air!

Got warm air out of the passenger side for a day or so, but that seems to have cleared itself up. I'll keep an eye on that, but in the meantime I couldn't be happier!

Thanks for all the help!

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Jake
1999 e300d PlantDrive WVO/SVO conversion
**note to self: oil changed at 268k kms**
1990 Toyota 4Runner FrankenDiesel swap

Ahhhh ..... You have done well grasshopper!
May I Add ............the duo valve is leaking ......
"Got warm air out of the passenger side for a day or so"
On the passenger side.........Remove the duo valve covers (2 screws each) I think its a T10 torx ......If its wet with coolant ...replace it!! But for now ...carefully wipe the solenoid's dry replace the covers.......the air will work until antifreeze leaks back in ........
On my car, the flaps were doing strange things. one side cool one side warm. .......After the valve was replaced all was well ...
I agree with the previous poster.
Replace the evap temp sensor it has been revised. its way up under the dash..up under and to the right of the center vent

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2003 SLK 230 (85000)
1999 E300 Turbo Diesel (388,000)
1991 350SD Turbo Diesel (185,000)