More heater control questions :)

[Inkyskin]

Hey all, more questions about the heating dials on my dash! This is something that doesn't seem to be covered in the manual, so here goes:

The lights behind the dials are sometimes flashing at me - if I then turn the heating on and then off again they stop flashing - does anyone know what that means?

Also taking into account that the lights on these dials do work, they don't light up when my headlights are on (Even though the buttons on the console do), is that normal for these cars?

Lastly, as far as I can tell the centre vents always blow cold, and the two vent's next to the doors always blow hot, even after messing with the 2 temp slider dial thingies - would that be a knackered fuse or something more sinister?

Cheers!

[swithin]

On the centre vents do you have a red and blue button, the light on these buttons may have gone and the centre vent may be on permanent cold.

[Inkyskin]

I have the two dials to change the temperature, but they don't light up, not even when the two large centre dials flash - they don't seem to alter the temp in any way whatsoever. This leaves the central vents cold, and the vents next to the doors and under the windscreen always hot.

Would the lack of lighting on those two dials really stop them operating?

[television]

Only part of you question there are bulbs behind, you pull the knobs off to get to them.

Time is short tonight on the other fault


http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=202018&M=111%2E920++++++111%2E921&GA=722%2E421722%2E603&GM=717%2E416717%2E417717%2E418&CT=F&cat=44V&SID=83&SGR=150&SGN=03

[Inkyskin]

Okay, I think I have things all confused ;) I went back out now that it's darker to double check bulbs etc. So, if you look at the picture below:

http://www.ben-griffiths.com/images/heaters.jpg

Q1. Right, when I start the car, the buttons 1A, 2A, 2B, 1B all flash, all four of them. Sometimes after the heating has been on they stop flashing... I have no idea why they flash...

Q2. When I turn the cars headlights on, 1A, 2A, 2B, 1B stop flashing, and infact the lights on them turn off completely, yet the lights on the buttons on part 3 all light up as normal. Shouldn't the lights behind 1A, 2A, 2B, 1B turn on too?

Q3. No matter what position 1A, 1B are in, the vents next to the front doors always blow hot, and the central vents always blow cold...

Hope that makes sense to you all ;)

[andy27168]

They should be illuminated all the time, at least while the cars lights are on.
Its not unknown for the heater control panels to fail, and need replacing.
Friends C180 failed exactly the same no temp. control.
Hope this has helped.

[Inkyskin]

I'm hoping it's just a fuse or something - with mine being such an early model system it's gonna be a pain to get a replacement I think... :(

[KillerHERTZ]

They do pop up from time to time, new from Mercedes your looking around £170 mark.

Be careful when looking for them as you have the very early version, after '95 they changed them, the easest way to spot the differences is that on the later versions the centre buttons are curved and later dials go up to 5 instead of 4

(I hope that makes sense)

[andy27168]

Try Mercman in Southampton hes recently broken 2 or 3 early c classes.
Or you could try fixing yours but it strikes me that you have more than one thing wrong with yours, temp control, both sides and illumination problem.
Just found this on e-bay.

http://cgi.ebay.co.uk/Mercedes-Heater-Climate-Control-Unit-P-N-202-830-04-85_W0QQitemZ200214088865QQihZ010QQcategoryZ10398QQ rdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638 Q2em118Q2el1247

Good price too.
Hope this has helped,

[Inkyskin]

Ouch, I'll have to keep my eyes open for other sources then ;)

[Inkyskin]

Andy, that looks perfect, thanks!

[KillerHERTZ]

Just to add - exactly the same thing happend to my old W202, that needed a new unit.

Be careful with that ebay link 'sold as seen' eg, might not even work! :(

[Inkyskin]

It does say in working order though - if it didn't work I'd be within my rights to get a refund, even if it was via paypal :)

[television]

The outside vents only give the temp set by the wheels.
The center vents only ever blow cold.

The flashing could be a dry soldered PCB and is not a listed fault.to replace the lamp lever off the knobs with a plastic wedge

[Inkyskin]

Cool, I'll give it a go :)

[television]

Cool, I'll give it a go :)

All of these unit suffered from dry joints, with a suitable small soldering iron and flux cored solder heat up every connection and apply solder, the joint is only good when its bright and shiny.

Do not use flux on its own.
Get some non drying switch cleaner and spray into any switches (Maplins)

[Dec]

Quote
Q1. Right, when I start the car, the buttons 1A, 2A, 2B, 1B all flash, all four of them. Sometimes after the heating has been on they stop flashing... I have no idea why they flash...

Q2. When I turn the cars headlights on, 1A, 2A, 2B, 1B stop flashing, and infact the lights on them turn off completely, yet the lights on the buttons on part 3 all light up as normal. Shouldn't the lights behind 1A, 2A, 2B, 1B turn on too?

Q3. No matter what position 1A, 1B are in, the vents next to the front doors always blow hot, and the central vents always blow cold...

All 5 switches along the top of picture have their own independent bulb/LED? The come on when you’re outside lights are switched on.

Q1. All four of them flash because you have a loose connection somewhere in the unit, there is no other reason for them to flash.

Q2. Turning headlights on would have no influence on the dial lights, just seem that way.

Q3. 1A Gives variable heating to passenger side (Blue = cold to Red = hot) 1B dose the same for drivers side.
The center vent gives fresh air only from outside and is controlled by its own thumb wheel. The vents next to the front doors will blow hot or cold air depending on where 1A and 1B are set.

You could take it apart, you may find and resolve the problem, nothing to loose if you intend to replace it anyway.

Dec

[gurpz]

Andy, that looks perfect, thanks!

Bare in mind this one is from an even earlier model compared to yours as this has the Rectangle W124 style knobs where as yours has the later style rounded knobs.

[Inkyskin]

Good point, hadn't noticed that.

I think in the end I might get one from the stealers - I shouldn't have to worry that way, and I know that my poor soldering skills won't make things worse either ;)

[KillerHERTZ]

?

Andy's link was to the correct old style one? - his car does have the early version as I have pointed out on my earlier posts :)

http://i21.ebayimg.com/06/i/000/e7/89/9583_1.JPG

[Inkyskin]

The two dials, the bars on mine are mour rounded, they seem squarer - it would only be a simple swap from mine to sort that though

[KillerHERTZ]

Yours is the early version, heater goes up to 4, where as the later version goes up to 5, includes the rear screen heater button, your rear screen button is on the dash itself.

They cannot be swapped between each other as the wiring and parts of the heater unit itself are different:

From 1993-early 1995:
http://www.ben-griffiths.com/images/heaters.jpg

After 1995 (ignore the white colour - this is from a sport model):
http://i242.photobucket.com/albums/ff148/rfdudhia/S1-1.jpg

[Inkyskin]

The 2A and 2B dials I mean - see mine are slightly curved? They don't appear so on the ebay unit

[KillerHERTZ]

Ah, I see what you mean, the handles can be swapped, ive had 2x snap in the past, around £3 each IIRC

[Inkyskin]

Cool, I can always use my existing ones too :)

[andy27168]

The outside vents only give the temp set by the wheels.
The center vents only ever blow cold.

The flashing could be a dry soldered PCB and is not a listed fault.to replace the lamp lever off the knobs with a plastic wedge

With the set up inkyskin has the centre vent is only a fresh air vent, but in the case of the later climate control models the centre vent can pump out heated air.

[mr. shr]

The lights behind the dials are sometimes flashing at me


Are the lights flickering or flashing?
If flashing, would you say it's always at the same frequence? I'm just wondering if the flashing is not just a dry joint but actually sign that a component is begining to fail and is causing a pulsed output? i.e. capacitor charging and discharging at the wrong rate or a transistor playing up??

Malcolm knows more about this sort of thing.

Any thoughts Malcolm?

[television]

Are the lights flickering or flashing?
If flashing, would you say it's always at the same frequence? I'm just wondering if the flashing is not just a dry joint but actually sign that a component is begining to fail and is causing a pulsed output? i.e. capacitor charging and discharging at the wrong rate or a transistor playing up??

Malcolm knows more about this sort of thing.

Any thoughts Malcolm?

Ones first thought are always is it a code telling you that something is wrong. Its alway hard with dry joints owing to the problems they can cause.

Rather than search for any not so obvious ones I find it easy to blanket solder the whole board. though around 200 joints it does not take long and it leaves the mind free to think about if they should have mixed bathing in the nude for the unemployed in public.

[nick mercedes]

Q3. No matter what position 1A, 1B are in, the vents next to the front doors always blow hot, and the central vents always blow cold...

Duo valve?

[television]

Duo valve?

Thats pulse operation, is this feeding back into the control unit hence the flashing

[Inkyskin]

I also discovered tonight If I give the dash a good whack it usually stops the flashing ;) (Not permanently though) - It is a true flash by the way, not flickering or anything, looks very much like it was meant to do it.

[television]

I also discovered tonight If I give the dash a good whack it usually stops the flashing ;) (Not permanently though) - It is a true flash by the way, not flickering or anything, looks very much like it was meant to do it.


Confirms dry joint on PCB, slip the unit out and wack that or the dash and you will have the answer

[Inkyskin]

Will try it tomorrow when I have the time to tear the dash apart :D

[nick mercedes]

Thats pulse operation, is this feeding back into the control unit hence the flashing

The flashing could have nothing to do with the lack of heater control.

[television]

The flashing could have nothing to do with the lack of heater control.

And with a bad soldered ground in the control unit it could, and at the same time this could render the valve out of out of action, the info comes from the control unit and not the other way around, and the fault does exist.