E220 Air Con / Demist problems - Please Help

[mike220]

FAO Keith,

I've been searching throgh the forum, and notice that you have had several of the same problems i'm experiencing. I wonder if you'd be good enough to help by sharing some of your experiences ?

My 1996 E220 coupe is terrible in wet weather - it will only demist the lower half of the screen. I can get warm air (good temp control, warm to red hot), but it will not clear properly. I cannot get cold air properly (it is always slightly warm-not proper air con freezing cold). I'm getting a slight humm from the blower motor too (possible bearings ?) which is speed dependant. I do get increased air flow when the recirc function is on, but not as much when its off.

Sorry for the long list, but its driving me mad not being able to solve this - and i can't afford to take it in somewhere. With winter coming, i know this is gonna be a problem. Any help would be a huge bonus - and very much appreciated.

Thanks in advance,

Mike

PS, if anyone else out there can help, please do !

 

[Keith]

bit more history

Mike
can you give me a bit more history.

How long have you owned the car ?
how long has it been demisting poorly/
what about cooling, how well does the a/c work in warm weather?
has it been better in past?
does it maintain a constant temp level in the cabin etc.

I have a few thoughts forming but the above would help decide where best to start.

Do you have a Haynes or other workshop manual handy?

Keith

 

[mike220]

Thanks Keith (W124 Hvac guardian angel !!!

I've had the car for 1 year. Never been able to get fridge freezer type cold air (end up opening the window) pretty sure I need a re-gas (how much are these ?). Was never that great at demisting, but certainly used to be better than this. Heat control seems pretty good, i.e. temp up and down (warm to red hot and back again). Have notice once that when recirc was switched on, drivers side stayed/went hot and pass side went cooler ??

Car has 172k on it, with merc history till around 145k. Its been a tad neglected since then, but thats all gonna change now i've got my hands on it !!

Cheers,

Mike

 

[Keith]

lets start with blower

Ok Mike

I think we should concentrate on the heating side. At this time of year a/c is becoming less important and although it helps demisting it should work better than you describe without the a/c.

A few more q's;
Which controller do you have in the console , is it the one with two dials and three vertical buttons between them or another ? please describe.

Does the blower increase/decrease with changes to the blower speed controller?

When you select demist is all the air coming out onto the w/screen above the dash or is it leaking from the foot/centre/side vents?

What I am trying to establish is do we have a low volume of air from the blower or is it leaking around the system and its the distribution of air thats the problem. Tell me what you think.

Plan A (depending on your answers to the above) is a low volume of air from the blower. In which case I would do the following (with the help of haynes if you have it):
Open up the blower box underneath the front wiper assembly , and below the fresh air filters. Its basic spanner on a few nuts and a screw driver , 15 mins to get in there. With the top off the blower box try the blower on different settings and take a listen to it, it should be silent ans smooth except for the air moving , if there are other nasty sounds then i would wager it need repair. I have never repaired one but i guess you can try doing the brushes or just replace the unit. If it seems ok at various speeds then try this - turn it around left to right and put the top of the box back on. Try again at various speeds and see if you have improved airflow to screen. This tactic cured mine because its possible to replace these blowers the wrong way around which results in a low airflow like you describe. If this was the problem it means some dumb ass has replaced it before and stuck it in the wrong way (as was the case with my W124) cost to fix is zero so this is a great problem to discover.

If you think air is leaking around the other air vents then thats a different story.

Tell me how the above goes.

K

 

[mike220]

Yes Keith, two dials (well, wheels) for temp, two dials (one blower speed and one distribution) and three buttons (demist, EC, and recirc - i understand, although not 100% on function of ec button)

blower does increase/decrease as per the dial (but so does the hum/vibe which i'm pretty sure is the motor bearings ??)

When you say select demist, do you mean direct air to the screen or press the demist button (or am i confused and that button is called an air dryer ?). If i direct air to the screen using the right hand dial, it comes out onto the screen and out of the vents (sides and centre if i open it, but this is usually left closed). I do get a flow of air on all settings, which seems to increase if i press recirc (is this normal?) just not sure if i'm getting the full 100% tornado ?

I'll strip the panel off and have a listen to the motor and let you know what i find. What are you now thinking after the above comments ?

Thanks,

Mike

 

[Keith]

still thinking blower bad/wrong way around

Mike
ok so you have the tempmatic controls like mine which is good - this is a semi automatic HVAC but at least its possible to intervene unlike the fully auto sort on some models.

When I say demist I mean rh dial pointing to screen and the demist button ON. If you have no air flow to other places then I am thinking either blower speed or blower in the wrong way around as per my last email. Either way I would burrow into the blower box at this point especially as its relatively easily accessible.

The buttons overide the controller as follows:
Demist - this forces ON the aircon so that the evaporator dries the incoming air.
EC - this stands for EConomy, when EC is ON then aircon is stopped from working ie is forced OFF (confusing but true)
Recirc is obvious and stops incoming air / pollution.

The default for all these buttons is OFF meaning the car automatically chooses whether or not to engage the A/C depending on conditions and air comes in from outside to help avoid suffocation.

Keith

 

[jberks]

Mike,
Not detracting from Keith's sound advice above, and you probably already know, but it can help to simply clean the windows with a good glass cleaner / polish. Often people get the windows misted up, wipe it with a cloth or hand and from then on have a problem. If you smoke, nicotine on the glass has a major effect too. Moisture has a harder time clinging to clean glass, so the cleaner the glass, the less the demister has to do.
I had to use the rear demist recently and figured it had been a while since I cleaned the back window. It looked clean enough but the cloth was black when I finished. Haven't had to use the demister since.

 

[Keith]

any progress Mike?

just wondered what you found in the blower box?

 

[mike220]

Hi Keith. Well, after some investigation yesterday evening I found the following :

Completely clogged Dust filters - these have now been discarded completely for the time being, as they were beyond saving. This was causing the poor airflow

A peice of foam (from the stell plate which opens behind the motor) inside one of the hamster wheels on the motor. This was throwing the whole thing out of balance on its rubber mount, and causing the vibe/humm

Put it all back together, and although its not a new one (which would have cost me £225+) it is 99% better. Loads more flow, and no vibe through the dash top. Should get many more miles out of it yet !!!!

Thank you Keith for your help ! It really is appreciated mate - all we have to do now is try and get AC cold air !!! haha. Think I'll try a re-gas on this one first ?

Cheers,

Mike

 

[Keith]

Good job!

Mike
thats great news, the filters can be refitted without removing the wiper assembly when you get to put new ones in. The bottom one slides in and out sideways so you can push both parts in and out that way.

so the next challenge is the cold.

Certainly a re-gas could well be needed if its not been done for a while. I recommend you take it somewhere rather than have a mobile visit. The latter can be relatively unskilled franchisees without the best gear and also could be tempted to reuse refrigerant to save pennies. Best go to a proper garage where they do re-gassing. last time I had mine done it was about £60 but it was a couple of years ago.

Before doing that I would do the following test:
press the top button (demist) and throw both dials to max cold . Then under the bonnet on the passenger side between teh bulkheads you should a thick rubber pipe which is the return from the evaporator. this should go cold pretty darn quickly (within a few minutes) and if the air is moist will get 'frosty'. This shows there is good refrigerant and the compressor is doing its stuff, ie you have a good cold side to the air con.

If you get no cold doing this then you could take a punt on re-gassing or try some more diagnostics to try to eliminate other components of the rather complex system.

If the latter then I am going to ask you to do some searching on this forum and Benzworld.com where there are many threads on debugging the aircon system. If I have a few mins over the weekend I'll post some references to the better ones for you but its all been covered many times.

I think you are on the road to sorting it , good start at least.

Keith