LED replacement bulb for air controller (fan) blows #4 fuse

[91166 Carrera]

I've got a 1976 Euro Carrera 3.0 Targa. I tried to replace the air controller light bulb, the one that turns on when the fan is running, with a LED bulb. The incandescent bulb is a Osram #2721, 12v-1.2W, (911-631-129-90) and has a tendency to melt the plastic socket and crack the face plate. When I made the replacement with the appropriate LED bulb it blew the #4 fuse (16A), the cigarette lighter/aux fan fuse. Question: has this been done successfully before, and what do I need to do to make the LED bulb work? Can LED's be used in the instrument for better lighting? And what about the ashtray bulb, Osram #3898, 12v-2W (900-631-102-90), can this be swapped for a LED bulb without blowing a fuse?

Harry
91166 Carrera

[allaircooled]

I replaced mine with LED's a couple of years ago. I had to modify the LED's I bought to replace the standard bulb but at the moment I can't remember why I had to. I think maybe the socket has + on one side and - on the other but the bulbs had both + and - on each side. Stupid memory, and how I did take some photos at that time. I had to use a dremel to remove one of the tabs on each side of the LED.

[spuggy]

Originally Posted by 91166 Carrera

tried to replace the air controller light bulb, the one that turns on when the fan is running, with a LED bulb.
Question: has this been done successfully before, and what do I need to do to make the LED bulb work?

Replaced mine about 12 years ago - I was surprised to see there were 4 bulbs in the heater controller panel, as none of mine except the fan indicator were working before, and I didn't realize the whole panel was supposed to be lit at night, LOL...

Was also a little disturbing to see how melted/deformed the plastic holders were.

I had the cheap (I think they were 10 for a buck fifty) SMD LED type with the wires on the plastic base, same as the ones for the fuel/oil warning lights? Simply plugged each one in, turned on the lights, rotated if necessary until it lit. No drama.

Pretty sure I removed at least one of the LEDs again later (like the one under the "FAN" legend); simply too bright/distracting at night and I didn't need that panel lit up like a carnival.

Originally Posted by 91166 Carrera

When I made the replacement with the appropriate LED bulb it blew the #4 fuse (16A), the cigarette lighter/aux fan fuse

I have no idea why you're blowing a 16A fuse. That sounds scary. Also seems far more likely to be the squirrel wheel (blower fan) motor than the LED light to me.

Originally Posted by 91166 Carrera

Can LED's be used in the instrument for better lighting? And what about the ashtray bulb, Osram #3898, 12v-2W (900-631-102-90), can this be swapped for a LED bulb without blowing a fuse?

If the ashtray is simply a BA7S like the instrument illumination, then I would have swapped that as well; the only incandescent bulbs left in my interior are the alternator warning light (HAS to be a bulb for 2 reasons) and the flasher repeaters in the tach, Until I get around to updating the wiring to 85-up spec via the 3-pin relay mod that eliminates repeater "ghosting" with LEDs https://forums.pelicanparts.com/porsche-911-technical-forum/819548-flasher-hazard-mods-my-80sc.html.

I don't believe the ashtray bulb is fused, stock?.Dash Lamp Replacement Question

[Nditiz1]

Be very careful when doing this. I put in the one shown above without the modification and fried my headlight switch. Definitely put a fuse inline on the power source for the headlight switch. Do not use bulbs with backing on both sides.

[91166 Carrera]

Thanks for the feedback. I solved the problem, I believe, and the solution worked. On the LED replacement bulb, the electrode pins wrapped around the part that inserts into the socket. By snipping off the portion of the pin that wraps around the insert part of the bulb, it only contacts one of the plates inside the socket. It worked. Thanks again.