E430 Hissing Air Con - although recharged!

[Veridian]

Hi folks, Ref my 1998 E430 with climate control - it has a problem similar to other threads Ive noticed.. Since buying the car at Easter the Air con never really worked, just went through the motions but with air at ambient (or hotter if so set) temperature coming thru the vents. Having enquired on the forum around 8 weeks ago I helpfully was told of a site that gives details of the fault codes and various settings. this duly showed there was only 1 bar of pressure in the evaporator.. ie no refrigerant - not really a surprise. I took it along to my reputable independent who plumbed it into their machine which drained, dryed and refilled the system - almost a kilo of coolant apparently, and showed no leaks. System worked fine for a week, but although this afternoon I have just checked, and the evaporator has a steady 8 bar of pressure rising to 14 bar on steady revving - (2500 rpm), and the evaporator temparature is showing 36-40F - nice and cool - im getting only marginally cooler air from the vents, and this elusive 'hissing aerosol' sound from inside the dash, that stops when you hit the EC button, only to restart when the a/c is back on.

I dont think I have a leak - but what is causing this racket - and why am I not getting any cold air!!??.. Any help gratefully received...
FYI - heres the link to the AC info page:
http://www.continentalimports.com/ser_ic40142.html

The Quote below was from wetdog..

Anyone know my problem?

Turn on air con and set the blowers to 3. you hear a faint aerosol like noise coming from behind the vents. Do the same with the air con off and the noise has gone.
Turn aircon on and set it to 6 and when you turn the blowers off the fans stop, as they would, and you hear this loud gas like noise, almost like an empty spray can, coming from behind the vents.

It seems like the gas is leaking or something. I had new gas put in it 2 months ago.

Any Ideas????[/QUOTE]

 

[Blobcat]

When was your pollen filter last changed?

 

[Veridian]

Pollen filter...

Hi Blobcat,
Ive only done 1500 miles in the car since buying it, and its indicating a service due in 2000 miles.. I havent changed anything but was going to treat it to a B service at MB Woking who quoted £500 ish and thought I'd ask them to change the pollen and charcoal filters then.

Do you think the blocked filters could be the problem?, since the last service I think was done by an independent who probably only did half what may have been needed.. cheapskate!! I have seen instructions for changing the filters and I think its prety straightforward, so could do it myself.

Thanks
V.

 

[Templar Al]

Hi Veridian,

I had an almost the exact symptoms on my '97 C200. The hissing seemed to come from the vents, but the hissing stopped and the airflow increased when I removed the pollen filter. (i.e. running the system without the pollen filter)

There's no hard-and-fast rule of when to change them - it depends on how quickly they get clogged - but the loss of airflow and the hissing are good signs!

Get a replacement from Europarts or GSF for about £13 and fit it yourself easily in 10 minutes!

Regards,
Alan.

 

[Veridian]

Cabin Filters..

Hi Alan, The fun one can have on a sunday evening.. since blobcats post Ive just gone out and checked the filters... Mmm they were black and full of seeds/leaves etc!! So in the meantime Ive given them a damn good cleaning out and hoovering, and put them back until I can order some this week.. But I started up the air con, and Im still getting the hissing which comes from almost directly behind the central vents, despite the filters being far left, and to be honest providing plenty of airflow.. and morer importantly im not getting any coll air, despite the evaporator temperature being in the mid 30s farenheit!.. Very strange!.. Anyone out there got any ideas!??
Cheers
Steve

 

[television]

Your air con and heating is vacuam contolled a leak will cause the hiss or split pipe

Have a look here
http://www.detali.ru/cat/oem_mb0.asp?TP=1

Go to your car, then vacuam

http://www.detali.ru/cat/oem_mb2.as...GA=722.623&CT=F&cat=45P&SID=80&SGR=120&SGN=05

Malcolm

 

[Veridian]

hiss

Malcolm, thanks for the link to the tech site, but im not really sure what its showing me - i assume its the pipework behind the dash - which short of taking the dash apart Im not going to be able to easily access to check for leaks!!!
The thing is, im not losing pressure in the system - (well I dont seem to be and the garage who filled 2 weeks ago confirmed it was leak free). When i go into the diagnostics, if anything the pressure increases over time, and is starting off at 8bar - which at 14psi/bar is over 100 psi!.. The hiss sounds like a 'lazy' release of pressure, .. sort of as if you were spraying an airfreshner around a room. Im sure ( he hopes) it is something simple.. but what.. Im not sure!

 

[Bob.R]

Ater the a/c has been running for a few minutes the evaporator temp sensor should read 5-10 deg C and the Hi side pressure should be around 200 psi (14 bar) on a hot day.
If either reading is not around this and the a/c was charged correctly the you probably have a leak on the system which is why the system needed charging in the first place.
When the charge becomes low bubbles form in the refrigerant making a hissing noise as they pass through the expansion valve.
A simple way to check the a/c is running well - run for a few minutes - check the refrigerant return pipe from the evaporator to the compressor (the larger one) should be 'icy' cold - around 2 deg C.- If not you have an a/c problem, if it is then you have an air/distribution related problem
Bob. R ( tech@CarAircon.co.uk )

 

[television]

The hissing is nothing to do with the charging of the Air con, All of your controls are vacuam controlled, if the air flaps are not working through a vacuam leak the system will not work, if all of the vents are closed the air con will not work, this will be a dash out job I think.

malcolm

 

[Veridian]

Thanks everybody!

The hissing is nothing to do with the charging of the Air con, All of your controls are vacuam controlled, if the air flaps are not working through a vacuam leak the system will not work, if all of the vents are closed the air con will not work, this will be a dash out job I think.

malcolm

This is starting to sound expensive!!. . The thing is, the system works absolutely fine and i can hear all the flaps doing what they are supposed to, and sending air to the right locations according to the ^V> buttons. Indeed if i set the temperature to HI i get hot air thru the vents.
I only get the hissing with the air con On. turn it off - put the system into EC mode - and I get no hiss. surely that implies its something to do with the air con, or am I missing something

The pressures are reading as recommended above.. the evaporator temperature is indicated at 36F, and the pressure did indeed go up to 14 bar after around 5mins of running at 1500 -2000 rpm. I think the car had been sitting idle on the forecourt for a few months over the winter before i bought it, so i dont know if that caused the seals to leak?. Ill check the pipes as recommended and will probably take into a specialist - I see Boxer Motor Works in Ashford Middx has been recommended on here.

Many Thanks everyone

 

[television]

Its all very hard by remote control, but it only takes one actuator or flap to stop it and give the hiss, if all was well , we would not be having this discusion. why not go back to the people that did the job.

Malcolm

 

[Veridian]

Its all very hard by remote control, but it only takes one actuator or flap to stop it and give the hiss, if all was well , we would not be having this discusion. why not go back to the people that did the job.

Malcolm

Hi Malcolm,
I'll give them a ring tomoz.. they have been fixing my cars for 17 years now with never a problem..and since the manager gets several bottles of duty free from me each year Im sure he'll make sure its put right!
Cheers
S

 

[Templar Al]

Steve,

Did you try running the system with the Pollen Filter out (with the cover back on of course)?

If it was black and full of seeds, hoovering won't clean out all the micro-particles that clog it up - in fact you could make it worse if you hoover the wrong side and pull the particles deeper into the filter material.

I still think it's worth a shot before you start paying, but if this proves not to be the cause, Malcolm's earlier point about the vacuum-controlled flaps is a good one!

I'm sure that an additional flap comes into play when the A/C comes on to route the air through the evaporator (I can hear a flap shutting on my S280 when I select A/C) and if the pipework that connects to the flap servo is split or has come off, you will hear a hissing noise but get no cold air because the air isn't passing through the evaporator.

These vacuum pipes can easily be repaired by sliding some heat-shrink tubing (from Maplin Electronics) over the damaged area and heating it with a hairdryer - if you can get to it!

Regards,
Alan.

 

[OlafMaxwell]

you should also note that the condenser radiator is a well known failure item, located behind the passenger side wheel strut under the plastic cover. You should get this checked, I had identical problems and non working air con and this was the cause.

 

[Veridian]

Fault Codes

Many Thanks for all the advice including that most recent from Olaf.
Last night i tried pulling up the fault codes, and got Eb1232 - ECT Sensor (B11/4); Eb1235 - Emission Sensor(B31); and E1459 - Series interface (K2) connection to instrument cluster(A1).

Im not sure what this means, as the car runs fine, but Im guessing that the ECT sensor is something to do with the evaporator, which although pressurised up is showing a temperature of 30 Centrigrade instead of the 2-6C it should be.
What to the figures in brackets mean - are they wiring diagram codes?

Im going to take it into a Merc specialist in Wimbledon in the next frew days, I guess any advance direction I can give will help narrow down the diagnosis!

Thanks
Steve

 

[television]

The numbers thrown up depend on what type of code reader was used. And only certain reader's can be used with certain car's.

Malcolm

 

[Veridian]

these were generated by the cars internal systems.. ie shown on the climate control display.