Heater/Blower/fan dash switch light bulb how to replace

[Paul99]

I have only just realised the heater fan blower switch in the dash has a small light bulb in it.  Can it be replaced and if so how, what bulb etc.  please?   Mine is there but doesn't light up. Should it light up with the fan on, all the time or only with the head or side lights on?

[Jonny B]

It is not hard to replace, but a bit of time is needed. To access the switch, you will need to remove the glove box. Once that is done the switch is easily accessible. You do unscrew the front escutcheon to pull the switch if you need to clean the contacts. What you may find (as I did with mine) is that the little metal tab that holds the light bulb is long gone (rusted, broken, etc.). I was able to find a replacement, but patience was required. If someone was able to get their hand in there with the glove box in place, please post how you did that.

I do not remember the size of the bulb, so someone else will have to chime in on that one. I know it is a small wattage (2?).

I am traveling and do not have access to the car, but I think the lights have to be on, and the blower has to be switched on.

[Paul & Dolly]

Paul,
It is not too difficult, but as Johnny B has said corrosion will probably be evident.

I have photos of when I rebuilt mine last year, but cannot post them until we return to UK from Europe at the end of August.

The light only operates when the fan is running, and is only a pin prick and very hard to see.

If you are coming to Willingen we can speak then.

Keep well

Paul

[Paul99]

Thanks guys.  I will wait until you can get me the bulb number/type if possible.   it looks tiny!  Similar to the bulb you used to get in a maglight torch.?

So i guess you cant just pull the bulb out from the front once the black turn handle is off and replace that way?

[garymand]

What you are looking at is not the bulb.  The bulb is in the back of the switch.  They didn't make bulbs that small.  Its a light pipe, primitive fiber optic, a plastic rod that reaches through the switch from the bulb in back through the hole in the knob.  The bulb gets black inside as it ages, so the light you see at the front of the knob dulls with time and finally the filiment burns though and no more light at all.  You have to get to the back of the switch, to pull the bulb.  Since its a time consuming multistep process the suggestions are saying to take the whole switch out, clean and refresh it.  My detent just went soft and the bulb just died.  I'm planning on giving it an hour R&R and 1/2 hour cleaning and refurbishing and 1 hour to get to the store for a new bulb.  But something will probably interupt the process and it will take another hour to get back to it.

[49er]

 We were out a ride under the stars last night and I thought of this post and the lighted fan switch. I couldn't remember if our car's switch was illuminated or not. Nope! I guess my 250's  was lit but can't remember. Have that problem with a lot of things these days.

John

[Jonny B]

Actually the later 250 SL  switches may not have been lit, with the big change for DOT regs at 2980, not sure if the fan switch was one of those. For sure the 280 SL switches were not illuminated. And as has been posted, even the cars when new, the lighted switches were just barely viewable.

[garymand]

Mine is an early 250, you can see and feel the light pipe in the center of the knob.  It protrudes maybe .050in., not much and the color is clear plastic, not glass.  If the light was dropped with the new bigger knobs, I suspect it would not be drilled and have the plastic light pipe but no light.  So you should either see the light pipe protuding slightly in the center of  the knob, or you don't have a lighted heater switch.  It is worht the effort to fix it.  I knoticed mine was out as soon as I turned on my heater -I was used to seeing the light even though it is just a soft 'twinkle' on my dash. 

[Paul & Dolly]

Paul99

I am now back in UK again, so here is the picture of the Blower Switch, showing the
light tube and bulb I mentioned 4 weeks ago

Paul

[garymand]

Is the red paint OEM  ?

[Paul & Dolly]

No, the red paint was me, as I am partial to red lights !

Much of the electrics were non functional when I had the car - glove box lamp & switch, "Trunk" lamp wireing,
Tail light wireing, windscreen washers, clock illumination........so I fixed it all last winter.

The Blower switch was in poor condition, bulb contacts corroded, ceramic broken, rheostat dirty,
I made a new backplate to fix the ceramic, but the bulb contacts & spring were corroded away, so I soldered wires to a new bulb and attached them to the connector block pins on the back of the switch - it all works fine now.

Keep well
Paul

[star63]

I made a new backplate to fix the ceramic,

Interesting!

What material did you use to fabricate the new backplate?

- Petri

[Paul & Dolly]

Petri,
The assembly is held together with 4 through bolts and posts, the photo shows the lower ceramic corner missing, it was also cracked.
 I made a new backplate from thin electrical insulation board (like a bare printed circuit board), which now holds the remaining ceramic in place, using the corner posts, although  I also had to insulate one of the pillars with electrical "shrink wrap".

Paul

[star63]

Thanks!

I may have to do something similar. Mine is cracked too...

Petri

[Paul99]

great, thanks for that.  next job on the list!

[pdc]

i have a late 250 SL and it has no light bulb in the fan dash switch.

[suonno]

I'm trying to replace the switch but cannot figure out how to remove the knob. Typically there is a small set screw that you turn CCW but I cannot see such a screw. I'm pulling and turning, I don't want to break it, but cannot get the knob off. This is the knob with a blue indicator on it near the upper left corner of the glove box.
>
> Thanks,
> Carl

[garymand]

It is held in the chrome nut by a lock ring like on the linkage.  Just pull hard.

[suonno]

Gary - Thank you. Like you said "pull hard". It came off.

Thanks,
Carl

[Novamonte]

At times it is difficult to push back on in the same manner. If so, remove the round nut first, put them together and refit the nut with the knob attached. I also prefer to take them off as an assembly rather than pulling the knob off from the nut.

[ja17]

To re-install the knob,add a bit of grease to the lock ring, remove the round plastic center disc of the knob. It comes out. At this point I use a 10mm deep socket into the knob and just tap it on with a small hammer. I then re-install the center plastic disc. I'll try to post a pic later.