Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 9 of 9 Posts

·
Registered
2004 chevy trailblazer_lt
Joined
·
19 Posts
Discussion Starter · #1 ·
Good Morning All! This morning, I attempted to turn on my fog lights and dscovered they don't work. The small light by the button comes on when I push it, but all I get is a "click" from under the dash and no lights. I'm not good with elecrtical problems, has anyone encountered this before? I checked the fuse and it's fine, so please, guidance anyone????? Many thanks.
 

·
Registered
Joined
·
8,781 Posts
it may be the relay.. try swapping it with a similar relay and see if they come on... if they do.. swap the relays back and replace the broken one
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
19 Posts
Discussion Starter · #3 ·
Thanks!

Thanks for your suggestion about the relay. I tried the swap, but still no lights. I know the fog light lamps are good, can you give me another suggestion? I appreciate your help.
 

·
Registered
2009 chevy
Joined
·
6,431 Posts
Petty simple circuit. Power is from fuse #11, under the hood.

Pushing the button tells the body control module that you want the fogs on.

The BCM sends a ground to the fog relay (#39, under hood), operating the relay.

Relay contacts close a circuit to the lamps, which have ground wired to the socket.

The "on" led is turned on by the ground that operates the relay.

So, good relay and good fuse, the lamps should light (if the lamps are good and they are grounded).

Remember, the BCM only provides a ground when the low beams are on, but (and I don't remember if this happens) the "on" led is only on when the fogs are on. According to the drawing, the led goes out when the high beams are on.
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
19 Posts
Discussion Starter · #6 ·
well, I tried..........

Thanks for your replies on my dilemma. I tried swapping the relays with no success, and I understand the circuit now, but I still get a green indicator light when I push the fog light button, so maybe both lamps did go bad somehow?

I'm going to install new lamps and see if it was the problem. If not, I'll be back for more advice if you have any.

Thanks again for your assistance, I appreciate it.
 

·
Registered
2009 chevy
Joined
·
6,431 Posts
Remember, the BCM only provides a ground when the low beams are on, but (and I don't remember if this happens) the "on" led is only on when the fogs are on. According to the drawing, the led goes out when the high beams are on.
I tried this today, the led go on/off with the fogs. So, when highs are on, the fogs go out and the led goes out.

I'm going to install new lamps and see if it was the problem. If not, I'll be back for more advice if you have any.

Thanks again for your assistance, I appreciate it.
I'd try new lamps first as well :thumbsup:
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
19 Posts
Discussion Starter · #8 ·
Thanks!!

It was the lamps! Go figure they both went bad. A new set of silverstars did the trick. Thanks to all for your advice.
 
1 - 9 of 9 Posts
Top