Headlight issue

[hflier]

Is anyone having mysterious headlight issues on their vehicles that are hard to find?

 

My son has low beam headlights that are both very dim.

His passenger high beam headlight does not come on at all.

 

He has one normal high beam headlight working.

 

1. All headlight bulbs have been replaced.

2. All headlight fuses and relays have been replaced.

3. The drl module has been replaced.

4. The bulkhead connector F109 below the fuse block has been checked and found to be free of corrosion, but has been coated with dielectric grease to prevent corrosion.

 

Still has no low beams - just a slight glow in each bulb.

Still has no passenger high beam.

 

Each bulb has the expected 12 volts on the bulb.

 

So, the problem is certainly on the ground switching side of the circuits.   Just have not been able to find the problem.

 

Any thoughts?

 

[ivans imports]

in the under hood fuse box is two fuses marked left / right headlight check those first also will see realys left / right headlight should click when headlights are turned on

[Rooster2]

Recommend to check further for a bad electrical ground.

[mikaleda]

IMHO i would Start by checking grounding to the lights that is most likely culprit, 12 volts is actually a little low but not enough to make the lights do that.

 

Edit: also I believe that gloyal has a write up on here about dim head lights and making a new wiring harness to make them brighter.

Edited February 20, 2013 by mikaleda

[hflier]

It is all fine and dandy to talk about grounding and checking grounding, but in the tribeca, that is a difficult thing to do.

 

All headlights have the correct voltage on the supply side of each headlight bulb.

 

Of course, in this vehicle - all switching for each headlight bulb happens on the ground side of the bulb.

 

So, one can not short out the ground side of the bulb to ground, because of the circuitry that goes on past that point.

 

If, I cut the ground wire to each light bulb, and ground out each light bulb at the light bulb, the bulb works just fine as expected; since the bulb is a new one for each location and each headlight relay and fuse was checked and found to be good, and the voltage on each light bulb was checked and found to be good.

 

The issue is how to figure out where the problem is on the ground side of the bulb.  There is a lot of wiring and switches between the ground side of the bulb and the actual vehicle ground.

 

Drl wiring, drl connector, wiring harness across the vehicle, wiring harness going through the firewall under the dash, etc.

Edited February 20, 2013 by hflier

[Cougar]

I suggest you check the voltage at the switch since the trouble could very well be at that point. The ground for the lights should tie to a common point through the switch and then to ground. If there is a voltage drop across the switch and chassis ground while the lights are ON then you have found the trouble spot. If there isn't a significant voltage drop across the switch and the voltage is near zero then the problem is between the light return wire and the switch connection to ground. When dealing with this kind of trouble it pays off big time to have a factory wiring manual to refer to. It will show you where every connection point is in the wiring for the circuit. Ebay is a good place to get factory reference manuals at a good price.

[hflier]

Cougar,

Thanks for your thoughts.

I do have the factory manual - I signed up for a 4 day service from the official Subaru factory on line service that is used by the subaru dealerships.

 

But even these sources leave a lot to be desired with respect to actual location information. Yes, I have the detailed schematic.

But, it is often very very difficult to find the items listed in the schematics. i.e. where is the drl relay? Where is the DRL module.

Where is the actual ground connection for the head light switch?

 

Sure it is on the schematic, but where is it in the car?

 

Thanks again - still searching.

[ivans imports]

check all bulbs some lights have more than one headlight bulb had a svx that had two burnt headlight bulbs but still had high and low headlights but no drl it used 6 headlight bulbs on for low one for high and one for drl on each side

[hflier]

Ivan,

Thanks for your thoughts.

All 4 head light bulbs are brand new bulbs, that each work when 12 volts is applied to one terminal and ground on the other terminal.

[Cougar]

You're welcome for the help Hflier.

 

The factory service data shows the connector number of every connection of the wiring. It also has various pictures of the car along with the wiring harness routing through it and where the locations are of the numbered connectors that are shown on a list that you can compare with the connector number and the fuction of the device it ties to. There is also a ground wire pictorial and list that shows the grounds.

 

If you think there is a ground problem to the light switch then use your voltmeter on the lead to see if that is true using a good ground point for your meter reference. If the connection to ground is bad then there will be voltage on that lead while the circuit is on. If the voltage on the lead is near zero volts then the ground is ok.

[hflier]

Cougar,

Excellent tip on the use of voltage checking on a wire that should be at ground potential but may not be there due to a bad ground.

 

That idea had not crossed my mind, but such a simple but effective way to check.

 

thanks again.

hflier

[Cougar]

You're welcome. Having a meter to test with gives you a lot possibilites and ways to test circuit problems out. Checking for voltage drop problems is one good method.

[hflier]

Cougar,

Since you seem to have a very good handle on the Subaru vehicles, do you have a source where one could obtain the factory manual?

[hflier]

My son was back from his business trip and we were able to spend some time on his vehicle.

First, I finally sat down and got my head turned about a 1/4 turn to the right, after I finally realized that the color coding for the wires on this vehicle from the conventional american vehicles that I am used to working with. i.e. from a lighting situation, we effectively have a positive grounded vehicle in a manner of speaking. i.e.  they color the ground wires with red colos and the color the voltage wires with browns and black.

This had given me issues when doing my  initial trouble shooting because I would just automatically look for ground on the brown and black wires and voltage on the red colored wires. However, the opposite is true.

 

I went back to basics, as Cougar and others have suggested and just started from the beginning on the belief that I had missed something initially.

Have correct voltage at the output of fuse 6 and 7 which are the headlight fuses. But I DON't have voltage at the bulkhead pin, where the voltage is supposed to leave the fuse block.

So, it appears that there is an open circuit on the inside of the fuse block, between the output of pin 6 and the bulkhead connector of pin 6.

Furthermore, when I check the front wiring harness from the fuse block bulkhead connector over to the main connector on the front frame for the headlights, I find another open in that wire as well.

 

If this continues to check out, I am guessing that perhaps a wire got pinched or shorted out and burned open, and also did the same thing for the fuse block connector. The interesting thing about this situation is that it did not cause a fuse to fail.

 

Since we did not have another fuse block on hand, I installed a temporary wire from the + 12 volt battery terminal to  a fused 15 amp wire over to the high beam + wire on the high beam headlight.

 

This fix temporarily took care of the lack of passenger side high beam light.

It also took care of the very dim low beam lights that were lighting up due to sneak currents passing backward through the high beam light bulbs.

 

However, there is still an issue on the low beams.

I have no drivers side or left side low beam light.

Also, the passengers side low beam light although  much much brighter than what it was, but is still only about 1/2 brightness level.

 

Unfortunately, my son had to pack up and leave for now, so was unable to do any more voltage checking.

 

Since the fog, high beams on and off,  I suspect that the light switch is all right but have another issue with the front wiring harness on the vehicle.

 

When more time allows, will continue the testing and checking

[Fairtax4me]

It's a switched ground system. Only difference between this and the old systems is the DRL module controls the ground side of the bulbs rather than a switch, but the concept is still the same.

It would be nice to know what voltages are present on the high and low ground pins at the lamp socket with the lights on and with them off.

 

Unplug the lamp socket, turn the key on and check each pin for 12v. Whichever one has 12v, that's the power into the lamp. The other two wires are grounds controlled by the DRL module. One ground will be "on" and the other will be "off" depending on the position of the dimmer switch(hi/lo). If the DRL module is not grounding the lamps properly you will have 12v at the power into the lamp and something less than 12v but more than 0v on the hi/low pins.

If the highs are On, the hi pin should have 0v. Highs off, high pin should show 12v.

Same applies for the lows.

As I said in the other thread, with the DRL module unplugged the lamps should have no ground path, and with the key ON all 3 pins at the lamp socket should have 12v. If the hi and lo pins show less voltage than the power in there is a connection issue at the bulb. If all 3 pins have 12v check for 12v at the high and low pins at the module. If 12v at the pins in the module connector, the issue is in the module. It sounds more like a poor connection between the junction block and DRL module or between the lamp sockets and junction block.

[hflier]

Fairtax,

I am thinking at this time that it is a connection issue between the lamp sockets and junction block caused by an issue in the front wiring harness.

 

More checking will determine the cause.

[ivans imports]

the headlights are powerd by realys the realys are turned on by the switch i still think its a power feed to realy problem i see lots that overpower the headlight realy fuse and will not turn on the realy or a shorted drl module you should be able to jump the conector at realy and turn the lights on to test curcit

[ivans imports]

one more thing the drl gets hot so might have overheated check it for heat damage

[hflier]

Ivans,

The DRL has been replaced with a new one, with no change.

All headlight relays and fuses have been replaced with no change.

 

I think you are right in that it is a voltage supply issue.  Right now, it seems like I am having an issue with the front wiring harness.  I have found one open wire, and they may be more.

 

Roger

[Cougar]

 

Cougar,

Since you seem to have a very good handle on the Subaru vehicles, do you have a source where one could obtain the factory manual?

 Ebay is a good place to find manuals on CD and book form at a good price.

[hflier]

Cougar,

It is too bad that there is not a nice illustrated Haynes or equivalent factory manual available for this car.

Roger

[Fairtax4me]

You can get the factory manual from Subarus website, just have to download all of the sections independently. Kind of a PITA.

 

What model year is the car?

[hflier]

Fairtax4me,

The vehicle is a 2006 Subaru Tribeca

 

Thanks for your thoughts.

 

Roger

[hflier]

Finally fixed.

After following all of the schematics and eliminating the reverse currents being back fed - the problem was an open wire that fed the high beam headlight on the passenger side.

 

To fix it, I cut the wire about 10 inches from the fuse block, spliced in a replacement wire, and connected it to the headlight - about 10 inches from the headlight.

 

Then, from the time that I started looking at the  problem, until today, one more head light bulb - had burned out - which of course - changed the symptoms

 

When doing the testing, I noticed a low battery voltage. As a result, I had the battery checked and found it defective.

 

So, I put in a new battery and now the voltages  read correctly.

 

At the end of the day 

1- wire $1.

A pair of high intensity light bulbs:  $30

A new battery  - replaced under partial warranty for $30.

 

Alls well that ends well.

 

Roger

 

[Fairtax4me]

So rewarding to find the source of a wiring problem! Glad to hear you got it fixed finally.