Headlights not functioning

[Brian_D]

1997 Blazer LT, 4.3L

Both low and high beam lights do not turn on. If high beam is selected, dash indicator does not light either.
Rear lights work fine.
Daytime running lights work fine; however, dash indicator does not always light.

When this last occurred approx. 1 month ago, if the park brake was engaged (to turn off the daytime running lights) then released, the low and high beam lights began working again.

I am not trusting the wiring diagrams in the Chilton book as it does not show ANY wiring connection to the Headlight Switch ON position, and it does not show the connections between the emergency brake switch and the daytime running lights.

I believe this may be a problem with the multifunction switch (headlight dimmer switch) even though I had replaced it with a new $365 GM switch in 6/05.

Does anyone have more accurate wiring diagrams and/or can tell me the location of the Daytime Running Lights Control Module and the Fuse Link supplying power to the Headlight Switch?

As I see it, the Daytime Running Light Relay is functioning properly but I still need to eliminate the Headlight Switch.

Thanks for any input.

[MT-2500]

Sealed beam or composite headlights bulbs?

[Brian_D]

composite headlights. btw, thanks for the pm should help tremendously. will update thread with the final resolution.

[Brian_D]

As promised, posting back with resolution - bad headlight switch. After opening switch and cleaning contacts, found problem is with the design of the switch.

Symptoms:

• No headlights - high or low beam.
• Headlights shut off when high beam is selected.
• Dim headlights.

Design:

The RED wire supplies power for headlights only and is HOT at all times.
The YELLOW wire is the power output for headlights to the Multifunction Switch (High Beam/Low Beam selector) and is only active in the ON position.
The Headlight Switch Contacts connect the YELLOW terminal to an OPEN terminal between the RED and BROWN terminals (brown powers the park lamps).
The OPEN and RED terminals are connected internally by a "points contact".

Problem:

The "points contact" becomes corroded and gradually increases in resistance over time.

Correction:

Use electrical contact cleaner to clean the headlight switch contacts. Then replace the corroded "point" with an inexpensive set of points from the auto supply house.

-or-

Pay the Dealer approx. $35.78 + tax for a new headlight switch.

BTW, on my '97 Blazer, I only had to remove 2 screws to gain access to the Headlight Switch - instead of dropping the steering column, etc. as outlined in the Chilton manual.

Can take pictures this weekend if there is any interest.

[MT-2500]

Thanks for posting back how it went.
Glad you found the problem and got it fixed.
MT