Light bulb replacement in the A/C Heater Control panel / Unit
 

The light behind the right side control knob is burnt out on my damsel in distress coupe. Before I take it apart, has anyone ever taken one of these apart to see what lights are inside and if they are replaceable??

http://thumbs1.ebaystatic.com/d/l225...f9KpP4C-YQ.jpg

Looking at photos of the backside (borrowed from E-Bay), there are no bulb sockets visible so I guess I would have to remove the backside casing to access the internals. Just wondering if anyone has been inside one of these and can share what to expect in there . . .

http://i.ebayimg.com/00/s/MTIwMFgxNj...UhzR8/$_12.JPG

re: Light bulb replacement in the A/C Heater Control panel / Unit
 

see if this helps : Replacing heater control bulb SLK R170 - Mercedes-Benz Owners' Forums

re: Light bulb replacement in the A/C Heater Control panel / Unit
 

THANKS (Super) George, If that works it will save me a lot of time and effort. Going out to try it now!

re: Light bulb replacement in the A/C Heater Control panel / Unit
 

Well . . . Of course it's never as easy as you think / hope it will be . . . I followed the information in the link ALA_XFIRE provided to the MB forum. I was fooled because after removing the control knobs, the bulb remained hidden by a little plastic flap.

At this point I looked in the Crossfire service manual (when all else fails read the instructions). The Crossfire service manual says:

HEATER SWITCH ILLUMINATION
DESCRIPTION
The Heater Switch (3) is illuminated with LEDs whenever
the headlamps or marker lamps are on. The lamp
brightness is adjustable with the dimmer switch
located in the Instrument Cluster. The heater switch
LEDs cannot be adjusted or repaired. If faulty or damaged,
the entire Heater Switch Assembly must be
replaced as a unit. For complete Heater Switch
removal procedures, refer to the Heater Control
removal in the Heating and Air Conditioning section.
(Refer to 24 - HEATING & AIR CONDITIONING/CONTROLS/
HEATER CONTROL - REMOVAL).

HOWEVER, I find that information is not totally accurate. I removed the A/C Heater control unit and eventually did find the light bulbs that illuminate panels around the circumference of the two control knobs. Turns out I did not really have to remove the whole unit. The bulbs ARE behind the control knob but are hidden by a little plastic flap. Of course the 10 year old plastic has become brittle and the little flap broke off immediately when I attempted to "open" the flap. These bulbs are in fact not LED bulbs but are miniature wedge base incandescent bulbs with a green silicone cap on them. Look like this . . .

http://www.atlantalightbulbs.com/ecart/p/t3wedge.jpg with a removable green silicone cap http://ts1.mm.bing.net/th?&id=HN.608...d=1.9&rs=0&p=0

Now I'm trying to find out exactly what the bulb number is (it's not regular a GE miniature bulb . . . it's smaller) so I can locate them somewhere and buy a few replacements. I'll try to take some photos of the control panel and update this post so others will be able to reference this thread in the future.

re: Light bulb replacement in the A/C Heater Control panel / Unit
 

Thanks Bob, I went out to the garage to look, but I couldn't even get the knobs off.
How did you do that without damaging them ?
( my bulbs are fine, I was just curious )

re: Light bulb replacement in the A/C Heater Control panel / Unit
 

Here's the photo step by step . . . It is NOT necessary to remove the control unit from the center stack . . .

Attachment 40469

Remove the knobs by pulling them straight outward (you may also need the gentle assist of a small prying tool as shown) . . .

Attachment 40470

The bulbs are under little white plastic flaps . . . 9:00 o'clock position left side and 3:00 o'clock position right side . . . note that my right side flap has broken off . . .

Attachment 40471

Turn the shafts to rotate that black part out of the way . . . Screwdriver is pointing to the left side flap . . .

Attachment 40472

Unfortunately, the plastic gets brittle with age and I broke the right side flap off when I pried it up . . . Note the bulb socket showing on the right side . . .

Attachment 40472

Use an appropriate size soda straw to slip over the bulb and wiggle / pull it out . . .

Attachment 40474

The bulb is a miniature wedge base bulb that has a green silicone cap on it. This is the bulb

https://www.fcpeuro.com/products/mer...-072601-012230

Found them here too . . . a bit less expensive . . .

http://www.allbatterysalesandservice...fm/4,1107.html

Now I need to find the little silicone caps (because I damaged mine) . . .

re: Light bulb replacement in the A/C Heater Control panel / Unit
 

Red Dog, Excellent show and tell on the bulb replacement. Thanks for taking the time to take the pictures and document it.

Re: Light bulb replacement in the A/C Heater Control panel / Unit
 

Re: Light bulb replacement in the A/C Heater Control panel / Unit
 

There are three bulbs used in the instrument cluster. 194's are the big ones then there are miniature ones with sockets and miniature ones without. It only has the MB and ORSAM part numbers but maybe the parts store can convert. Or feel free to post me back with anything you can find to fill in all the blanks.



Big Bulbs
MB # = N 072601 012240
Orsam # = 2821
Alternate # = 194
Wattage = 3W

Little Bulbs
MB # = N 072601 012230
Orsam # = 2721
Alternate # = I dont know
Wattage = 1.2W

Little Bulbs with sockets
MB # = I dont know
Orsam # = 2721MF
Alternate # = I dont know
Wattage = 1.2W
Thank you very, very much! That was just the information I needed.

For future reference, that type 2721 bulb cross-references to a number 37 bulb which is available at your local chain auto parts store for - well, they're two for 2.99 at Kragen (O'Reilly, Checker, etc.) stores.

Not the lowest cost option, but they're available almost anywhere at short notice. I'm going to drive over to the nearest Kragen (14 miles) tonight and pick up a couple of packages.

Once again, thanks! It's always nice when someone offers useful information.

Re: Light bulb replacement in the A/C Heater Control panel / Unit
 

Re: Light bulb replacement in the A/C Heater Control panel / Unit
 

GOOD FIND! I just need to confirm that our bulb is 3mm. I'm thinking it is a bit larger. I see that seller has caps for larger bulb too. Just need to be sure I order the correct size.

EDIT: Checking the specifications for our bulb, it is 5mm diameter . . . I bought these:

http://www.ebay.com/itm/271691902574?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
I also have 11 bulbs coming so will have a stock of replacement bulbs available for any forum member in need!

Re: Light bulb replacement in the A/C Heater Control panel / Unit
 

:) AS USUAL Dog/George, you's DA MAN'S! On another note, I would love a donation of one of the faulty A/C controls. I want to try to fault isolate the internals so that maybe people with these quirky controls can SQUEEZE more life out of the bad design that flooded our cars. Mine still burps (it was replaced under warranty and they would not let me have the old one) but when it does (hot when cold and/or cold when hot) I just turn the fan knob off, let it sit a couple, and turn it back on. This usually restores it, only once did I have to do it twice to 'reset' the dang thing. So, anyone have one of these they want to donate? No guarantees and if you want it back way down the road, I will gladly send it back (might be a little different than when sent as I have to 'take it all apart'. :)

Re: Light bulb replacement in the A/C Heater Control panel / Unit
 

Hi sorry to restart an old thread but can anyone tell me if the green caps is what gives the green color to the buttons and knobs? So changing it could change the whole color of the module?

Re: Light bulb replacement in the A/C Heater Control panel / Unit
 

I THINK it would change the color of only the knob dots (pointers) and the icon rings.

Re: Light bulb replacement in the A/C Heater Control panel / Unit
 

To anyone that is interested in changing the color of the ac/heather module, the little bulbs also ligth the buttons, so changing the bulb color will change the whole unit ligth color, can anyone tell if there are leds and wich size should fit? Cheers