| Hmm. Learn something new everyday. So these DRLs are only
| the front turn signal filaments and no other lights?
On some models, yes. GM has many many different implementations though. Some
are high beams at reduced intensity. Some are headlamps at reduced or full
intensity. Some are completely separate/dedicated units (on some large
trucks/SUVs) and others are the turn signal lamp at "near-continuous" duty at
full intensity (they still blink when signaling, then return to being
continuously lit after the signaling is completed).
| Are these lights behind amber or red lens'?
Amber lens AND/OR amber coated bulb in those implementations. Red lamps are
not allowed on the front of vehicles.
| And with the light switch off,
You're funny. There is no such thing as a "off" position on the light switch
on most GM vehicles...The "off" position is replaced by the "Auto" position.
Just so you know...you can't turn all lights off on most models today, even in
the daytime...even if you want to exercise that legal right to do so...your out
| the headlights are on low,
If the car has headlight DRLs and you put the switch on "auto" and it's
daylight out, then yes. If it has turn signal, high beam or separate DRLs then
the headlights themselves are off.
| and turning on the parking lights turns off the headlight
Depends on the implementation. On the Malibu I had (which had headlight-type
DRLs) the answer is yes at night and no during the day. But, different GM
models with the same type of headlamp DRL behave differently. The problem with
the Malibu is that IF you make the mistake and turn on only the "running
lights/parking lights" when it is still fairly bright outside (say in daytime
fog conditions) the headlamp DRLs are still lit. However if it eventually gets
dark enough during your trip to trigger the ambient light sensor (the so-called
"auto" light control system)...the headlight bulbs will actually go OFF (on
their own)!!! Great desigh...huh!?
| Well from what others said about it being illegal to drive with just the
| parking lights on, I guess it all makes sense in a strange wort of way.
No it doesn't. GM's lighting control systems makes no sense at all! The fact
that GM has dozens upon dozens of types and implementations and functional
differences between models and model years within the same models speaks
volumes upon volumes upon volumes to the fact that even GM is extremely
confused about their own light control systems and how they _should_ work.
Damn sad, if you ask me! The NHTSA should really crack down on all this
oddball lighting stuff...set some standards!!!
| Are the turn signal bulbs at full brightness?
If they are turn signal DRLs...yes...full brigntness.
| If so they must get hot!
Sure. That's normal and understood.
| They are normally only on intermittently.
Normal is the operative word. By definition then, are you saying GM's system
is abnormal? ;-) Not that I disagree. The standard bulb duty cycle is
designed for intermittant service, so burn out fairly quickly.
| I knew a trucker who insisted on putting brighter bulbs
| in his running lights. He was always replacing melted
| light fixtures.
That is only because he was using over-wattage bulbs...the housings weren't
designed to dissipate the additional heat.
I've heard that there are problems with burnt and cracked lamp sockets
though...not so much problem with melted hosings and lenses. Of course the
larger problem really is that the duty cycle of the signal filament within the
duel-filamant bulb is designed for intermittant service...so a special
long-life version of the bulb should be used if it is a DRL (or just know
you'll need to replace your bulbs once or twice a year if using the standard
bulb). I believe GM is the only place that the special bulb can be purchased
(last I heard). Hmmm....