'99 e300d - air conditioning not working - Page 2 - PeachParts Mercedes-Benz Forum

TMAllison · #16 04-16-2008, 08:56 PM

B1231 is engine coolant sensor (delays fan speed when cold outside until engine is warmed up and warm air is available)

B1234 is the sun sensor (raises fan speed when in full sun)

#7 is your refrig pressure. Is very low. May have a leak. Pressure is low enough compressor may not be engaging to protect itself. Side issue is why EC light is not permanantly on?

Do you hear any hissing or zing type sounds from the center vents?

Wait for MattL for more, he's much better at this.

notfarnow · #17 04-17-2008, 08:31 AM

Quote:

Originally Posted by TMAllison

B1231 is engine coolant sensor (delays fan speed when cold outside until engine is warmed up and warm air is available)

B1234 is the sun sensor (raises fan speed when in full sun)

So does that just mean those systems were in operation at the time, or are they error codes noting a problem with those systems?

Quote:

Originally Posted by TMAllison

#7 is your refrig pressure. Is very low. May have a leak. Pressure is low enough compressor may not be engaging to protect itself.

What is the normal pressure? Would my next step be to bring the car in to an AC shop to have its refrigerant recharged?

Quote:

Originally Posted by TMAllison

Side issue is why EC light is not permanantly on?

I'm not sure I understand this part. Why would the light stay on? Or is it only supposed to go out if the AC is engaged... ie compressor turning?

Quote:

Originally Posted by TMAllison

Do you hear any hissing or zing type sounds from the center vents??

Nothing that I noticed

Thanks again! I am trying to find threads with this kind of info but coming up short... I appreciate your help

Matt L · #18 04-17-2008, 10:09 AM

If the climate control unit shuts down the compressor due to low pressure, the EC lamp should be illuminated.

There's a version code to ignore low refrigerant level, which doesn't seem to do anything for my pushbutton unit. Perhaps yours is so coded and it works.

The first thing that I would do is check the static pressure on the system. If it really is <2bar, you are almost certainly low on refrigerant (especially at 23C ambient temperature).

KarTek · #19 04-17-2008, 10:18 AM

Quote:

Originally Posted by Matt L

If the climate control unit shuts down the compressor due to low pressure, the EC lamp should be illuminated.

This has not been my experience on my '98. When the refrig. level leaked down sufficiently, the AC comp quit running, simple as that. The EC indicator did not come on and the button continued to work "normally" with the indicator turning off and on.

The only thing that told me the AC wasn't working was that fact that there was no cold air coming out of the vents. A look under the hood confirmed that the comp. wasn't working. I have an air gauge type r134 checker and it read nothing so I added some refridg. and it's good to go now.

notfarnow · #20 04-17-2008, 10:25 AM

Quote:

Originally Posted by Matt L

If the climate control unit shuts down the compressor due to low pressure, the EC lamp should be illuminated.

There's a version code to ignore low refrigerant level, which doesn't seem to do anything for my pushbutton unit. Perhaps yours is so coded and it works.

The first thing that I would do is check the static pressure on the system. If it really is <2bar, you are almost certainly low on refrigerant (especially at 23C ambient temperature).

Ok, so if I understand correctly, if my compressor isn't engaging because of low pressure, the EC light should be on?

How do I check the static pressure?

Before I bring this car to a shop, are their any other issues that can prevent the compressor from engaging... relays, overrides, etc?

I want to do as much troubleshooting as possible before I start paying someone who will likely just start swapping parts in it.

FWIW, the AC hasn't been used since september (by the PO). Don't know if that's a consideration.

notfarnow · #21 04-17-2008, 10:26 AM

Quote:

Originally Posted by KarTek

This has not been my experience on my '98. When the refrig. level leaked down sufficiently, the AC comp quit running, simple as that. The EC indicator did not come on and the button continued to work "normally" with the indicator turning off and on.

The only thing that told me the AC wasn't working was that fact that there was no cold air coming out of the vents. A look under the hood confirmed that the comp. wasn't working. I have an air gauge type r134 checker and it read nothing so I added some refridg. and it's good to go now.

Ok that's good to know, sounds similar to what I'm dealing with.

How did you add your own refigerant? I thought only shops could do that, or do you have a shop?

KarTek · #22 04-17-2008, 11:23 AM

You don't need anything special to work with r134. What I did was this:

Went to Advance Auto and bought the following:

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=IDN&MfrPartNumber=MB134A&CategoryCode=3569

And a couple of these:

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=ADV&MfrPartNumber=A1300&CategoryCode=3571B

And a couple tools:

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=RBA&MfrPartNumber=10945&CategoryCode=3569

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=IDN&MfrPartNumber=GEZ1&CategoryCode=3569

Locate the low side AC fitting on the left inside fender wall near the intake manifold. It has a fluted pastic cap on it. Mine was nearly impossible to get off and I had to take pliers to it. When I put it back on, I just seated it gently rather than horsing it down.

Once the cap is off, start the car, turn on the AC (EC button off) and press that gauge into it to get a reading. If it's low, attach the hose to the can of r134 and to the connector on the car. Turn the valve all the way IN to pierce the seal on the can then back out to let the r134 flow into the system. Leave the car running at this time.

If it does the same as mine, you'll hear the compressor start clicking on for a second or two then shut off. It'll do this repetedly at longer intervals until it stays on constantly. You'll also want to get a bowl of hot water and dunk the r134 can into it in order to get the last bit out as the can will go cold when charging the system and lose pressure.

If you use all of the first can and the comp. is still not running constantly, hook up another and keep filling. Once it does quit cycling, close the valve, remove the connector from the car and take another pressure reading. If it's within spec, take the thermometer and stick it into the center vent with the AC temp set on LO and the fan set in the middle - like 4 bars. You should be able to get the temp to read down to about 45 deg or so, maybe less. If it's not as cold as you like, re-connect the hose and add some more, in small amounts but don't over charge it. Keep checking with the gauge.

That's about it in a nutshell...

notfarnow · #23 04-17-2008, 11:42 AM

great stuff, thanks!

I'll have to check on those r134 cans... I'm not sure if we can get those in canuckistan.

KarTek · #24 04-17-2008, 11:49 AM

Oh, didn't realize you were in the GWN...

notfarnow · #25 04-17-2008, 11:51 AM

Yes I should update my profile.

I am getting conflicting info on the recharge kits. The FLAPS says they are illegal, need a license to recharge systems here. But my Friendly Local European Auto Money Syphoning Shop says they have seen them at walmart here, but for ~$100

Matt L · #26 04-17-2008, 12:00 PM

I don't know the status in CA for HFC refrigerants, but I can tell you to avoid using a recharging system which only monitors the low side.

Be sure to measure the high side WITH A GAUGE while filling. DO NOT rely on the reading at #7 to tell you if your high side is too high. There are a few things that can cause the head pressure at the compressor to greatly exceed what you see at reading #7. The fact that this reading exists makes people want to cut out this very essential corner.

TMAllison · #27 04-17-2008, 12:21 PM

B1231 & B1234 are error codes.

The first is providing implausible data. The second is a very common failure that most of us ignore.

KarTek · #28 04-17-2008, 12:21 PM

Quote:

Originally Posted by Matt L

Be sure to measure the high side WITH A GAUGE while filling. DO NOT rely on the reading at #7 to tell you if your high side is too high. There are a few things that can cause the head pressure at the compressor to greatly exceed what you see at reading #7. The fact that this reading exists makes people want to cut out this very essential corner.

That's good to know. I'm typically VERY conservative when adding refrig. - only putting in as much as needed but you're right, no substitute for using the right equipment.

I needed a set of r134 gauges any way unless I can just convert my existing set of R-12/22 gauges!

notfarnow · #29 04-17-2008, 12:27 PM

Quote:

Originally Posted by TMAllison

B1231 & B1234 are error codes.

The first is providing implausible data. The second is a very common failure that most of us ignore.

The engine coolant sensor could have been getting some odd reading when I first Tee'd into my coolant lines for my WVO system. I had some air bubbles for the first week or so, and poor flow through the heater. Working fine now, I wonder if that's what triggered the code.

not much luck finding those AC recharge kits up here.

Matt L · #30 04-17-2008, 12:59 PM

Quote:

Originally Posted by KarTek

That's good to know. I'm typically VERY conservative when adding refrig. - only putting in as much as needed but you're right, no substitute for using the right equipment.

I needed a set of r134 gauges any way unless I can just convert my existing set of R-12/22 gauges!

The fittings are different for R12 (1/4 SAE) than for R134a (1/2 ACME), but there are adapters available.