98 Blazer headlights auto-on disable

[Robert Trank]

Hello
I have a 98 Chev Blazer and want to disable the headlight "auto-on"
feature when it gets dark outside. I want to just turn my lights on and
off manually, just like in the old days. I have located the light
sensor, and tried unplugging it. That was NOT the answer. The lights
were just on all the time then.

I contacted Chevrolet and asked them for help (via internet @
www.chevrolet.com) and they basically blew me off with some liability
BS.

I am an electrical engineer and understand detailed electrical
instructions. Unfortunately, I do not have the service manual. That
would also help if someone had one and could scan in a page and attach a
.jpg or pdf of the applicable sections dealing with how the wiring
bypasses the on/off switch on the dash.

Any help would be appreciated. Please cc my e-mail address with any
responses.
Thanks much.....Bob

[Superstar]

This is a safety feature. I wouldn't touch it at all. No point in turning on
your lights manually. Don't even bother messing around. This can be
dangerous.

superstar

Robert Trank wrote in message <7514aj$j...@newsops.execpc.com>...

[Wayne Roller]

Are you talking about daytime running lights or auto on light that work on a
photo cell? If it is the former, I have information for my K1500 that
should be the same. If it is the later, I would check to see what output
comes from the photo cell (most likely a voltage or resistance that changes
with light level) and reproduce a daytime condition with resistors.

[Bryant D.]

"Most" of the GM Daytime Running Lights and auto-on feature at night can be
overriden with the Parking Brake. Obviously you do not want to run around
town with your Parking Brake on all the time. There should be some wires
that come from the Parking Brake switch that control the light in the
cluster and also the status of the DRLs and auto-on feature. This is
assuming there are three wires(ground, cluster wire, DRL wire). If there
are only two wires, you will probably end up indicating the Park Brake
telltale in the cluster forever. Finding the right wire and tying it to the
appropriate state should solve the problem.

As far as safety is concerned, GM tries to sell the DRLs and auto-on feature
for safety and it probably helps. It is law in Canada that GM is required
to sell all of their vehicle with DRLs. However, there are no such laws in
the good ole US of A(yet).

[Robert Trank]

Thank you Wayne
I ended up with a 1k resistor directly across the light sensor (through a toggle
switch so I can enable or disable it). With the 1K resistor in place, the
output of the sensor went up to around 3.5 volts which was enough to simulate
daylight. (input to the sensor is 5vdc)

Where I live, we have a special Christmas light display in a local park and so
people just drive through slowly with parking lights on. (There's even signs
telling you to turn off your headlights!)

Anyway, it worked and I'm a happy camper about it. D#@$ the gm engineer for not
including a bypass switch for this feature.

btw, I also did not like the daytime running lights. I found a diode in the
fuse compartment under the hood labeled DRL (Daytime Running Lamps). Simply
unplugging the diode (shaped like a mini-fuse) took care of that problem too :-)

Any other curious folks...... be careful. On my wife's 97 grand prix, the diode
under the hood was for something else (something to do with air conditioning).
To fix her car, I found a 10 amp fuse on the fuse bank INSIDE the car labeled
DRL. Pulling this fuse took care of both the daytime running lamps AND the
"auto-on" feature.

Thanks again........Bob

[Wayne Roller]

The diode on your wife GP is a diode used to drain current from the AC
clutch when the relay opens. This is like any other DC circuit with a
inductor. If you don't have a diode, you will get a great deal of arching
on the relay contacts. Removing this diode will definitely cause relay
failure.

Robert Trank wrote in message <752v9t$f...@newsops.execpc.com>...

[Wayne Roller]

According to my shop manual on my 97 K1500, the park brake switch connects
to the DRL controller. With just a cursory look, I could not see a way of
separating the DRL from the Brake lamp on the dash. I'm sure there is a way
but it's not obvious. Looking at a previous listing, removing the DRL diode
does the trick.

Bryant D. wrote in message <75278m$an7$1...@remarQ.com>...

[Bryant D.]

Another option may be to just disconnect the DRL module. Assuming of course
it does not control anything else.

[Zaw Oo]

hmm.. There is a Relay center under you dash board.. one of them you have to
disconnect. to test which one you just trun the key to ON posittion with
Parking breads off or set the Gear to "n". which ever click try
disconnecting it..its real hard to get it there i havn't found a time to
take a look at it my self or anything yet. i'll soon.

[Zaw Oo]

that's kickass man.. finally I got answer to long waiting questions.

thanks.

Robert Trank wrote:

[person]

For sale Parts interchange manual. All GM Cars years 64-75. 3 books $125
Interested??

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VBDev...@worldnet.att.net

[MJS]

This is copied from a posting that I wrote earlier. It applies to my
'98 GMC Sonoma, but it might be of help to you. Good Luck.

Look under the dash up at the top of the emergency brake pedal
mechanism and there should be a single wire going into a connecter
that is connected to a copper switch mechanism. Unclip the wire
connector and pull it out of the way for now. The copper switch
which is bolted to the parking brake mechanism turns the DRL's off
only when the brake is set, so you need to "fool" your truck into
thinking that the parking brakes are set. I did this by installing a
toggle switch that allows me to turn the DRL's on or off.

Before you think that I am not addressing your question, I must
explain that the following procedure is necessary to give you the
result you are looking for, which is to have complete control of your
headlights (turn them on and off at will with the engine running).
Now, back to the operation . . .

The most important thing that you must do first is loosen the
screw that holds the copper switch in place and rotate the switch
upward about a quarter inch so that it is no longer affected by the
parking brake's position. This step will require some very
interesting double jointed contorsions of your body and creative use
of socket wreches and extensions. Next cut the wire that leads to
the connector which attaches to the copper switch and splice in a
simple toggle switch and mount that somewhere in your dash plastic.
(I used a rocker type toggle switch instead of those old funky metal
ones. Look better. Also, this instruction does not include info on
how to install a "lighted" toggle switch.) I just cut a little hole
in my dash down by the brake release and mounted it there, it looks
fine. Plug the original wire connector back in to the copper switch
at the top of the parking brake mechanism and your job is done.
Note, this will only work if you have followed the instruction to
properly rotate the copper switch upward so that it is no longer
affected (turned on or off) by the parking brake itself.

Next, if you want to have complete control of your headlights
(bypassing the automatic headlamp sensor), it's easy. Just make sure
that your newly installed parking brake bypass switch is "on" before
your start your vehicle and you will have complete control of the
headlamps. Once you turn your new toggle switch "off" AFTER you've
started your vehicle, the headlamp sensor becomes active again until
the next time your start your vehicle with the new switch "on".
Since your parking brake will no longer have any contact with the
switch that you have tinkered with, the parking brake indicator light
on the dashboard will either be on or off depending on the position
of your new toggle switch now.