What about dual filament bulbs?

I've heard DD talk about dual filament bulbs doing strange things to the 914's electrical system. I was fixing my turn signals last night and discovered when I installed some dual filament bulbs in the car soemtimes the blinker would blink fast as though a bulb was blown and sometimes it would even cause that annoying buzzer to go off.

Is there a place for dual filament bulbs on my car at all? Did the car come with all single filament bulbs? If there are supposed to be both kinds then which kind go where?

Thanks as always

How did you old timers work on cars before computers?

[Joe Bob]

In the rears....

[Dave at Pelican Parts]

The car came with both. Really "special" engineering on that one, I must say...

The front turn signals use dual-filament bulbs. The brake lights, I think, use dual-filament ones as well. I think (but am not certain) that the rest are single-filament.

--DD

[paulhagedorn]

Now you have gone and done it. Which is it, dual, single...

The front turn signals are for sure dual filament?
The brake lighs are for sure dual filament?
Or do they vary from car to car, year to year?

I have dual filament bulbs in the brake lights and the turn signals, which seems to me to be the only logical way to have both work as they should.

Alright, I finally did some of my own investigating.

I got out my 1975 owners manual and it states the following:

Bulb Chart (12-volt system)

Sealed Beam 60/50 W (6014)
Fog Lights 35 W
Stop Lights 32/3 cp (1034)
Turn Signals 32 cp (1073)
Back-up Lights 25 W
Interior Lights 10 W
Parking Lights 5 W
Luggage Compartment and License Plate Lights 4 W
Instrument Lights 2 W
Control Lamps 1,2 and 2 W
Side Markers Lights 2 cp (1895)

Obviously the W stands for wattage but what does the cp and numbers in parentheses stand for?

It also appears that the only dual filament bulbs on the car are the headlights and the stop lights. Agree?

[Dave at Pelican Parts]

The "cp" most likely stands for "candlepower", a rating of how much light the bulb puts out. (The watt rating is how much power it consumes.) The numbers in parentheses are, I believe, part numbers.

Some really very odd things happen when you swap single-filament for dual. Things like the motor continuing to run with the ignition switch off and the key out--as long as the left turn signal is on. Took me a while to figure that out...

Frankly, I don't remember for certain which bulbs in the taillight cluster are single-filament and which are dual. The front turn signals are very definitely dual, unless you have the European split buckets which have two separate bulbs. (If you have converted US turn signal buckets, you probably still have duals.)

Take the bulb out and look in the socket. If you see one metal prong sticking up at the bottom of the socket, it takes a single-filament bulb. If you see two, it takes a dual-filament bulb.

--DD