Bulb failure, no power to under hood fuse #17

[skander]

• Driver side low beam bulb failed.
• Decided to replace both sides with new H7 bulbs.
• Connectors on both sides had disintegrated.
• Spliced new connectors on both sides.
• Replaced bulbs.
• Now *passenger* side bulb stopped working, driver's side fixed.
• No power to pigtail.
• Fuse #17 under hood for passenger low beam looks good.
• Checked power to Fuse #17 using multimeter and it is receiving zero volts when headlight switch is on and driver's side is working.
• Checked 15 Amp fuse inside car at the panel between driver's door and dash. It is for both low beams, fuse good, power checked via multimeter shows good.

Stumped.

Thank you -

[FirstVolvo]

• Driver side low beam bulb failed.
• Decided to replace both sides with new H7 bulbs.
• Connectors on both sides had disintegrated.
• Spliced new connectors on both sides.
• Replaced bulbs.
• Now *passenger* side bulb stopped working, driver's side fixed.
• No power to pigtail.
• Fuse #17 under hood for passenger low beam looks good.
• Checked power to Fuse #17 using multimeter and it is receiving zero volts when headlight switch is on and driver's side is working.
• Checked 15 Amp fuse inside car at the panel between driver's door and dash. It is for both low beams, fuse good, power checked via multimeter shows good.

Stumped.

Thank you -

Power to the headlights comes from a relay the CEM controls and goes to the fuse box in the engine compartment on a single line 15/22:1 and this single line provides powers both fuses 17 and 18. Since the driver's side headlight works, power is getting to fuse 18 okay so if there's no power to fuse 17 the problem would have to be where the single power line branches off to fuse 17 in the fuse box. This seems unlikely but since the passenger side was working before but anything is possible. Did you measure both fuse contacts for power with fuse 17 pulled out? Not sure which side power comes in on so both sides should be checked. If there's no power to either side when headlights on are on and fuse 18 has power then the problem would be in the fuse box.

[skander]

I checked power to Fuse #17 the same way I checked it to #18, by inserting the two multimeter leads into either side of the fuse receptacle. Fuse receptacle #18 shows 12 volts and fuse receptacle #17 shows zero. So weird, passenger side was just working minutes before I spliced in the new pigtail h7 connector.

[FirstVolvo]

I checked power to Fuse #17 the same way I checked it to #18, by inserting the two multimeter leads into either side of the fuse receptacle. Fuse receptacle #18 shows 12 volts and fuse receptacle #17 shows zero. So weird, passenger side was just working minutes before I spliced in the new pigtail h7 connector.

Connect one lead of the multimeter to ground and then check for 12V with the other multimeter lead connected to either of the two fuse contacts (fuse 17) with the fuse pulled. If your splice or bulb has an open you may not see 12V across the two fuse contacts because there might not be a path to ground.

[skander]

Wow, this was an interesting check. I have 12 v if I ground the multimeter outside of the fusebox and touch the multimeter to one side of the fuse receptacle (#17). Does this mean that the ground wire leading to the fuse receptacle has a bad connection?

[FirstVolvo]

Wow, this was an interesting check. I have 12 v if I ground the multimeter outside of the fusebox and touch the multimeter to one side of the fuse receptacle (#17). Does this mean that the ground wire leading to the fuse receptacle has a bad connection?

It means you have an open between the 12V supply line from the fuse to ground, it could be the 12V line to the headlight bulb connector between the fuse box and headlight connector, the bulb itself or the other headlight connector to ground. With the fuse installed and the lights on measure for 12V at the headlight connector. Connect one of the multimeter leads to a good ground and then check the contacts at the unplugged headlight bulb connector, one should have 12V on it (blue yellow wire side). If you measure 12V at the head light connector then do a resistance, continuity check on the other connector to ground (black wire side), you should see 0 ohms. If both readings look good where you have 12V and the ground side checks out okay then check the bulb but you've likely have done this already so I expect you'll find the problem is with one of the wires.

[albertj]

It means you have an open between the 12V supply line from the fuse to ground, it could be the 12V line to the headlight bulb connector between the fuse box and headlight connector, the bulb itself or the other headlight connector to ground. With the fuse installed and the lights on measure for 12V at the headlight connector. Connect one of the multimeter leads to a good ground and then check the contacts at the unplugged headlight bulb connector, one should have 12V on it (blue yellow wire side). If you measure 12V at the head light connector then do a resistance, continuity check on the other connector to ground (black wire side), you should see 0 ohms. If both readings look good where you have 12V and the ground side checks out okay then check the bulb but you've likely have done this already so I expect you'll find the problem is with one of the wires.

As you know, halogen bulbs will fail very quickly if they get fingerprints or other oils stuck to the bulb envelope. Could it be your bulb died from handling? Consider taking the bulb out & check for continuity...

Albertj

[skander]

The problem was my splice on the power wire on the connector was not making good contact. I'm still scratching my head because it was soldered and shrink tubed and looked good, but something weird was going on there. I respliced using a different method.

I was only able to narrow it down thanks to both of you that helped me. Thank you -