Light bulb replacement in the A/C Heater Control panel / Unit
The light behind the right side control **** 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??

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 . . .
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 . . .
see if this helps : Replacing heater control bulb SLK R170 - Mercedes-Benz Owners' Forums
THANKS (Super) George, If that works it will save me a lot of time and effort. Going out to try it now!
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 *****, 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 *****. Turns out I did not really have to remove the whole unit. The bulbs ARE behind the control **** 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 . . .
with a removable green silicone cap 
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.
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 *****. Turns out I did not really have to remove the whole unit. The bulbs ARE behind the control **** 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 . . .
with a removable green silicone cap 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.
Last edited by RED DOG; Dec 15, 2014 at 06:40 AM.
Thanks Bob, I went out to the garage to look, but I couldn't even get the ***** off.
How did you do that without damaging them ?
( my bulbs are fine, I was just curious )
How did you do that without damaging them ?
( my bulbs are fine, I was just curious )
Here's the photo step by step . . . It is NOT necessary to remove the control unit from the center stack . . .
dcp_4935_zps511a6e44.jpg
Remove the ***** by pulling them straight outward (you may also need the gentle assist of a small prying tool as shown) . . .
dcp_4936_zps30d5a1be.jpg
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 . . .
dcp_4937_zps137fc03d.jpg
Turn the shafts to rotate that black part out of the way . . . Screwdriver is pointing to the left side flap . . .
dcp_4938_zpsaed4d172.jpg
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 . . .
dcp_4938_zpsaed4d172.jpg
Use an appropriate size soda straw to slip over the bulb and wiggle / pull it out . . .
dcp_4939_zps62e704b3.jpg
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) . . .
dcp_4935_zps511a6e44.jpg
Remove the ***** by pulling them straight outward (you may also need the gentle assist of a small prying tool as shown) . . .
dcp_4936_zps30d5a1be.jpg
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 . . .
dcp_4937_zps137fc03d.jpg
Turn the shafts to rotate that black part out of the way . . . Screwdriver is pointing to the left side flap . . .
dcp_4938_zpsaed4d172.jpg
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 . . .
dcp_4938_zpsaed4d172.jpg
Use an appropriate size soda straw to slip over the bulb and wiggle / pull it out . . .
dcp_4939_zps62e704b3.jpg
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) . . .
Last edited by RED DOG; Dec 15, 2014 at 06:37 AM.
Red Dog, Excellent show and tell on the bulb replacement. Thanks for taking the time to take the pictures and document it.
Bob,
Thanks for the write up here
I have slightly edited the title and stickied your thread to keep it on top
I also put a duplicate of this thread in the How-To Articles
Thanks for the write up here
I have slightly edited the title and stickied your thread to keep it on top
I also put a duplicate of this thread in the How-To Articles
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.
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.
Last edited by mferreira3417; Dec 15, 2014 at 05:02 AM.
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!
Last edited by RED DOG; Dec 16, 2014 at 10:26 AM.
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:
Green 4 7mm GM GMC Pontiac Buick Chevy Cluster Bulb Caps Covers 10 Qty | eBay
I also have 11 bulbs coming so will have a stock of replacement bulbs available for any forum member in need!
EDIT: Checking the specifications for our bulb, it is 5mm diameter . . . I bought these:
Green 4 7mm GM GMC Pontiac Buick Chevy Cluster Bulb Caps Covers 10 Qty | eBay
I also have 11 bulbs coming so will have a stock of replacement bulbs available for any forum member in need!
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 *****? So changing it could change the whole color of the module?
I THINK it would change the color of only the **** dots (pointers) and the icon rings.
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
it’s very easy to do!
Last edited by Gabbeegirl; Aug 27, 2025 at 02:26 PM.
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