Turning Signal/drl

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xoalvinox

New member
Greetings ALL!
Quick question regarding our turning signals/Daytime Running Lights...
In the manual, the bulb application list prints that the bulb used is "4157"

1)Is it cross-referenced to 3157 and 7443 bulbs? Essentially, can we use either/or?
2)It is a dual filament bulb. Is there a purpose for that? Because only the 27w output is used (DRL: constant 27w, Turning signal:Cuts power to the DRL so that it blinks)
Therefore, why do we use a dual filament bulb when only one current is used?

Any input is appreciated....

Alvin
 
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The dual filaments are used to distinguish the DRL from the turn signal... bright filament is used for the DRLs and the dim filament is used for the turn signals... Same concept used for brake and tail lights...
 
Thank you Bryancos...

Are you sure the outputs are different? 8 watts and 27 watts are huge differences when lit. Seems to me when the turning signal is going, it lights up just as bright as the DRL on the other side.

Lastly, can't find any aftermarket 4157 bulbs...are there any alternatives?
 
Hmm ... I'm not convinced of this. IIRC, the wiring diagram doesn't show two different circuits for the DRL and Turn signals. I'll check it again when i get home.
 
Yah, somebody mentioned something about alternative bulbs before too. I asked where they got that info, but never saw a response. From what's been worked out here and at Yotatech forums, the only difference between DRL and non-DRL systems is the flasher relay.
 
OK, here is the deal. Models equipped with factor DRLs have a 3 pin connector (F5, F6) at each front turn signal. Non-DRL models have only a 2 pin connector. Regardless, there is only 1 circuit active. In the DRL case, the same two pins are powered for the turn signals as are when the DRLs are on. It does not appear to be a hi/low thing according to the Factory Wiring Diagrams.

I search the entire manual and those connectors never appear in another circuit. To confirm, maybe someone with factory DRLs can take a look at the backside of the turn signal and check the wiring. Do you see 2 or 3 wires? Accoring to the manual, you will see only 2 (R-B & W-B on the left, R-Y, W-B on the right). The wires should be on pins 3 & 2 of the connector. For the non-DRL folks, you should see a 2 pin connector with the wire colors as above (obviously on pins 1 and 2).

What is certain is that f you add the DRL flasher, your DRLs will work. Perhaps the dual filiment bulb is brighter, longer lasting, or has some other special property. It's also possible that the 3 pin connector is internally bridged such that both filiments come on together (i.e. brighter).
 
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All the cross refs I've looked at show that 3157 will work... but then folks will say anything to sell a product...
 
I couldn't find anything about the bulbs in the factory service manuals. Where did you find the bulb info?
 
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