Tail light bulb orientation for the 1158s

[konrad]

So I got in a batch of 1158 tail light bulbs from octane lighting, but there is no 'top' listed on the base of the bulb, indicating insertion orientation.  Does it really matter?

I do note that one filament is slightly higher than the other inside the bulb.  Can that indicator be used for proper orientation in the socket?

[rialto]

The one filament is brighter than the other. The bright one is for stop and turn signal. The dimmer one is running light. You will have to try them back and forth 180 degrees until they are right.

[konrad]

The one filament is brighter than the other. The bright one is for stop and turn signal. The dimmer one is running light. You will have to try them back and forth 180 degrees until they are right.

So which is which...the higher or lower filament?

Since the sockets have an orientation based on how they reseat in the tail lights, there should be an orientation of the filaments respective to that...and I'm just wondering if anyone has made note of that before. 

[Gordie]

If the tips are staggered on the socket and the bulb there is only one way to install them correctly.

[konrad]

If the tips are staggered on the socket and the bulb there is only one way to install them correctly.

Nope, on the 1158s the pins are not staggered.  And it appeared to me that the indents in the socket were also at the same level on both sides.

[flamingchariots]

If the tips are staggered on the socket and the bulb there is only one way to install them correctly.

Nope, on the 1158s the pins are not staggered.  And it appeared to me that the indents in the socket were also at the same level on both sides.

 
 
Yes.  When I have encountered that kind of socket, you have to try the bulb one way then the other (like rialto suggested).
It helps to have someone else step on the brakes while you look.  Use the brighter for brakes unless you want to get rear-ended.   
I seem to recall that there is a thin filament (brake/turn) and a heavy filament (running).  I may be wrong on that.
Seems easy enough to remove the bulb from the socket and re-insert til correct.
 
 
 

[konrad]

Not a problem...just the wear and tear on the socket in removing/replacing it...these are not new fixtures.

I will see if I can determine an orientation as I replace these bulbs...perhaps I can add something to the knowledge base.

[Fid]

I recently installed these in my Allstate which is why I noticed the "Top" stamp on the ones I had.  Still, the wires were not connected to the socket so I had to figure out which one was which. You will notice the brake light filament is significantly brighter than the tail light filament.  Having a helper watch as you step the brake is a big plus.

[Corsairdeluxe]

For what it's worth.

[konrad]

Okay, just replaced my tail light bulbs with the correct 1158 bulbs, and there is an easy way to orient them correctly without trial and error.

As the socket only snaps in one way into the tail light, if you hold the socket in the correct orientation for reinsertion, the higher filament side of the bulb goes to the outside, the lower filament to the inside.