Electrical Schematic Question

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Merkava_4

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Jan 30, 2007
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Clovis, CA
2000 Buick LeSabre
Issue: Left high beam does not work

Question: Is Pin B the ground side of the connector ?

Left high beam connector
Pin B: If I touch the test light to this pin from the positive battery terminal, the test light will not light.
Pin A: If I touch the test light to this pin from a good ground and close the high beam switch, the test light will light.

Right high beam connector
Pin B: If I touch the test light to this pin from the positive battery terminal, the the test light will light.
Pin A: If I touch the test light to this pin from a good ground and close the high beam switch, the test light will light.

DSCN1982_zpsw0ut9kgf.jpg
 
That picture is a page out of the factory service manual. I'm still going over all the schematics. I know I have a bad wire on the left high beam circuit; I'm just trying to determine whether it's the dark green and white wire or if it's the pink wire. I'm still not sure which wire supplies the connector with power and which wire is the ground. Most 2-pin connectors that I've dwelt with have had a feed wire and a ground wire. This connector has a feed wire and an output wire. I'm not sure what an output wire is.
 
That car has daytime running lights and you need the whole schematic. Some designs do screwy stuff like throw a relay in there and make the bulbs in series for DRL and in parallel for real high beams.

Losing a high beam is a classic sign of a fubar DRL system.

You'll notice they call it "headlamp output", not ground, and the wire colors aren't indicative of ground, either.
 
Originally Posted By: eljefino
That car has daytime running lights and you need the whole schematic. Some designs do screwy stuff like throw a relay in there and make the bulbs in series for DRL and in parallel for real high beams.

Losing a high beam is a classic sign of a fubar DRL system.

You'll notice they call it "headlamp output", not ground, and the wire colors aren't indicative of ground, either.


Here ya go, with DRL...

1circuit_diagram_1.png
 
Find the schematic that shows the whole path back to the Body Control Computer. I don't know if the 2000s have as convoluted a system as does my 04 but I finally had to replace the BCC last year to cure a maddening DRL headlight issue. I wish you better luck sir.
 
Originally Posted By: TFB1
Here ya go, with DRL...

1circuit_diagram_1.png



Great schematic, but shouldn't North be pointing to the left of the page instead of up just like an antique Spanish map?
 
Originally Posted By: Papa Bear


I'm a retired electronics tech ... this is priceless !! ....
thumbsup2.gif



Yeah agreed, I serviced TV for almost 40 years... One of my buddies sent it to me, I like to pass it along...
 
Originally Posted By: Merkava_4
2000 Buick LeSabre
Issue: Left high beam does not work

Question: Is Pin B the ground side of the connector ?

Left high beam connector
Pin B: If I touch the test light to this pin from the positive battery terminal, the test light will not light.
Pin A: If I touch the test light to this pin from a good ground and close the high beam switch, the test light will light.

Right high beam connector
Pin B: If I touch the test light to this pin from the positive battery terminal, the the test light will light.
Pin A: If I touch the test light to this pin from a good ground and close the high beam switch, the test light will light.


Based on what you say here:

1)Right hand high beam is working, left hand high beam is not.

2)Right hand pin A is positive (ground/negative - positive lights up the test light).

3)Right hand pin B is ground/negative (positive - ground/negative lights up the test light).

4)Left hand pin A is positive (ground/negative - positive lights up the test light).

5)Left hand pin B is bad (open connection - positive does not light up the test light).
 
Originally Posted By: eljefino
That car has daytime running lights and you need the whole schematic. Some designs do screwy stuff like throw a relay in there and make the bulbs in series for DRL and in parallel for real high beams.

Losing a high beam is a classic sign of a fubar DRL system.

You'll notice they call it "headlamp output", not ground, and the wire colors aren't indicative of ground, either.


What the ....

but still you can troubleshoot this without a schematic:

Test the system 1 bulb at a time with bulb in the other socket, and test both in the DRL / high beam. Test light output may be reduced in the DRL case.

What happen to good ole multimeter? You can test all sorts of fubar design with a $10 meter. They probably cost just as cheap as a real test light anyways.
 
Pin B is the ground circuit. Do you have a DVOM to check the resistance? If not you can backprobe & create a temporary ground to see if your bulb will work
 
Mehullica, you are one smart cookie.
smile.gif


I took your ingenious idea and ran with it. The high beam bulb works fine if I backprobe Pin B to ground. I'm hoping the pink wire has a break in it between the bulb connector and the underhood fuse block instead of the black wire having a break in it between the DRL relay and G103.

DSCN2086_zpsphkjgyup.jpg
 
The answer to your original question: pin B eventually is your ground, but it does go through a relay prior to that.
 
yes, the DRL relay together with the Hi Beam relay switch between DRL or High beam.

If the DRL relay stays switched, the LH high beam bulb will switch off when you try to turn on the high beam (12v to both sides of the bulb).
 
Last edited:
At this point, the easiest thing would be to swap relays with another and see if that fixes the issue. If not, then tI'm to go more in depth.
 
Originally Posted By: eljefino
That car has daytime running lights and you need the whole schematic. Some designs do screwy stuff like throw a relay in there and make the bulbs in series for DRL and in parallel for real high beams.


That's what the schematic says, right?
Series both filaments for DLR, parallel them for regular operation and "high-beam flash".

I'm surprised the RH DLR works at all if the LH DLR doesn't.
EDIT: I guess the OP never said one DLR one works, the other doesn't. He just said high beam.
 
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