Headlights cut out while driving!

[Zapp Brannigan]

Going down the highway at 10PM and my headlights cut out completely! I tried to manually select on the dash... nothing....

Tried manual high beam and momentary high beam.... nothing....

Running lights (ambers) remained on.

Thank God I knew where I was as I have driven that road for years. Got off the highway, and within 30-60 seconds, they magically came back on. I tempted fate and continued on my voyage.

No issues since, and it has been a couple days.

 

[The_Roadie]

Ick! I'd guess something like the auto daylight sensor on the dash, but then the low beams should have reverted to DRL mode (are you stock lamps or HID?) and the high beams should have still worked.

Not much is in the control path to those two functions except the BCM. The power to the relays is straight from the battery. The control pins at the BCM are on adjacent pins on the connector, so you might examine the connector to the flexible PCB at the BCM to make sure it's not wet or full of spilled soda or something. Each of the four lamps has a different fuse, so a fuse block issue is not likely. And the two sides of the headlights have different grounds, so that's not likely to be the issue.

Anything else at all fail, like interior lamps or instrument panel lights? Radio? If so, then you might suspect the ignition switch, but what's your history on ever changing that out?

 

[GrizzlyDippah]

Check your battery cable connections. Sometimes when they are loose your headlights may dim or shut off. Just a thought.

 

[The_Roadie]

Check your battery cable connections. Sometimes when they are loose your headlights may dim or shut off. Just a thought.

And the engine continues to run?

 

[GrizzlyDippah]

Lol. I have worked on older vehicles most of my life...

 

[The_Roadie]

Yah, our alternator will keep the voltage regulated and the engine running even if the battery cables fall off.

 

[7d9_z28]

We have discussed ZAPPs alternator recently and it is suspected to be nearing the end of its life...

Though I don't believe it to be the particular issue here.

 

[Zapp Brannigan]

We have discussed ZAPPs alternator recently and it is suspected to be nearing the end of its life...

Though I don't believe it to be the particular issue here.

Correct.

Ick! I'd guess something like the auto daylight sensor on the dash, but then the low beams should have reverted to DRL mode (are you stock lamps or HID?) and the high beams should have still worked.

Not much is in the control path to those two functions except the BCM. The power to the relays is straight from the battery. The control pins at the BCM are on adjacent pins on the connector, so you might examine the connector to the flexible PCB at the BCM to make sure it's not wet or full of spilled soda or something. Each of the four lamps has a different fuse, so a fuse block issue is not likely. And the two sides of the headlights have different grounds, so that's not likely to be the issue.

Anything else at all fail, like interior lamps or instrument panel lights? Radio? If so, then you might suspect the ignition switch, but what's your history on ever changing that out?

Everything else functioned. I had not looked at the Voltmeter as my focus was not dying, so not sure if a battery connection. To the best of my knowledge all other items functioned, radio, interior dash lights etc...


Thank you for the input all, I will have to check the BCM and battery connections. Also probably needing a new Alternator anyway. I have had power dips a lot recently (usually after letting off the accel). Already done the cleaning of the TB, I am well aware of that common issue!

 

[triz]

Headlight relay. Forget the number. If you need one PM me I have one. The relay heats up and the lights go out. When it cools it comes back on.

 

[The_Roadie]

Headlight relay. Forget the number. If you need one PM me I have one. The relay heats up and the lights go out. When it cools it comes back on.

The OP symptoms were simultaneous failure of the low and high beams. It's true we've been assuming the high beams worked before the incident, and also started working when the low beams came back. Zapp, can you confirm you knew the highs were good before and after the lows cut out?

Otherwise, you're right. It could be that the highs were ALREADY dead, and the common relay failure we all know about took out the lows.

 

[Zapp Brannigan]

Ok so the latest update(s)

The OP symptoms were simultaneous failure of the low and high beams. It's true we've been assuming the high beams worked before the incident, and also started working when the low beams came back. Zapp, can you confirm you knew the highs were good before and after the lows cut out?

Otherwise, you're right. It could be that the highs were ALREADY dead, and the common relay failure we all know about took out the lows.

Sorry I did not notice this question until now. I can confirm that all lights on my vehicle were functioning prior to, and ultimately after this incident.

I had previously been having issues with power dips as I mentioned above:

Also probably needing a new Alternator anyway. I have had power dips a lot recently (usually after letting off the accel). Already done the cleaning of the TB, I am well aware of that common issue!

Found this reply in another thread:

I had the same problem with mine, but the headlights flickered along with the interior and dash lights. When I would watch the gauge it looked normal. I also took the altenator in and had it tested on truck and it came back normal. This went on for almost 6 months and I couldn't figure out what was causing it, I finally took the altenator off the truck and took it in to be bench tested. What was interesting is on the truck it tested fine but on the bench test under load you could see the fluctations. I replaced the altenator and have not had the problem since.

BTW I also tightened up every gorund on the truck while trying to figure this one out and chcecked the headlight switch.

I ran into similar problem last night, took a video:

Sorry for the shakiness, hate using YouTube stabilization, but I wanted to make sure to catch the dashlights, the voltmeter, the headlights, and all while not crashing at 4:30AM.

http://youtu.be/g7HCmIPepTw

 

[The_Roadie]

And you're resisting a new alternator why? Still could be a flaky ground such as the one on the fender near the battery. Did I miss a post in this thread where you took that off and cleaned it up?

 

[Zapp Brannigan]

And you're resisting a new alternator why? Still could be a flaky ground such as the one on the fender near the battery. Did I miss a post in this thread where you took that off and cleaned it up?

No, you did not miss any such post. This issue with the lights 'flickering' just started the other night, but I guess it kind of seals the deal.

Once I am not poor from moving (for the 5th time in 6 years)....

 

[Lonestar245]

Im going to jump in here rather than start a new thread. My truck is a 2009 Saab 9.7x, 4.2 Around 90k miles on the odo. Besides the problem described below, everything on the truck works as expected.

My low beams shut down intermittently. Its a pretty rare thing, and of course, dangerous, but even as I live in a big city where the roads are well lit, there are good chance of getting a ticket while waiting for them to come back on.

When this happens, my high beams still work fine. As do my fog lamps. No other symptoms- no flickering headlights- they are just "off", dash lamps are fine, as are turn signals. Honestly, I never thought to jump out and check the tail lamps.

I have replaced the low beam relay with a known good relay of the same value when it happened once, but this did not fix the problem. I swapped the relays back and purchased a new relay at the auto parts store- some off brand at Auto Zone. Did not fix the problem.

I should mention I did have the passenger side low beam headlight socket melt down a year or so ago, and I have replaced it with a quality aftermarket part, new lamp, I used dielectric grease on the terminals, soldered and shrink wrapped the connections. I kept all the wires as short as possible to not add resistance.
Reading through this thread, I see several possibilities referred to, but not really fleshed out (i'll look for the ground on fender near battery- but since my high beams still work...?). I'm wondering, could any of you make a list of these possible gremlins?

Thanks!

 

[Mooseman]

Did you check the fuse box? It's not uncommon to have it melt at the fuse connector and cause weird stuff. Maybe a loose ground connection. Grab the manuals in my sig for wiring diagrams. Although not the same years as your Saab, the headlight wiring shouldn't have changed much.

Btw, yours doesn't have xenons or HIDs by any chance?

 

[Lonestar245]

Did you check the fuse box? It's not uncommon to have it melt at the fuse connector and cause weird stuff. Maybe a loose ground connection. Grab the manuals in my sig for wiring diagrams. Although not the same years as your Saab, the headlight wiring shouldn't have changed much.

Btw, yours doesn't have xenons or HIDs by any chance?

I believe I have checked the fuse- 99% sure, but I suppose I will replace it, just in case. It would seem a fuse would either work, or be blown, but who knows?

No xenons or HIDs, I have have lowly halogens.

And to be sure, this is a rare occurrence, and there is never any additional load anywhere on the system- no trailer lights, etc....

One thing that popped into my head just now- I think I recall reading somewhere that these low beam headlights run at lower power during the day (DRL's) and, and switch to higher power when in headlight mode? And did I read they go from DC to AC or something like that? IDK, I have too many old cars to keep up with and it is all running together in my old brain.

 

[Mooseman]

Not just the fuse itself, but the place where it plugs into the box has been know to melt on occasion.

Did you happen to notice if you hit a bump or something to jar the truck? Maybe a loose connection. Check the bulb plugs and wires as you may have seen with melting.

Yes, the DRL runs on PWM, kinda like AC. Basically cycles power at 70%

 

[Lonestar245]

OK, I will check the sockets on the relay(s) for burning.

I ordered a new ACDelco 15016745 OE Service Headlamp Relay, just in case- $21.00 on Amazon. Next time this goes out, I will swap out the old with the new one ASAP and see if it fixes it.

I think I will check and maybe replace all the fuses related to this, and I suspect dielectric grease should be used everywhere.

I'll re-check the headlamp sockets too, who knows they maybe have burned up since I replaced the one. I have a set of ceramic sockets that I purchased later, but the plastic clip makes it almost impossible to use due to the small opening in the back of the headlamp assembly on the Saab. I could remove the clip and leave just the ceramic socket, but then the only thing holding it on the bulb would be friction, and I don't know if that is enough. Maybe if I tie the wires down so they cant bounce?

 

[The_Roadie]

The reason the low beams use that special black relay is that it's not a mechanical relay but a solid state transistor switch, that can cycle on and off faster than your eye can see the headlight bulb flicker. It flicks on for 70% of the time, and off for 30% of the time, at a few hundred cycles per second, to create the DRL function.

 

[smt 59]

Good morning folks, just experienced this headlight thing this morning going to work, low beams cut out but still had daytime running lights and all other lights remained working, tried the highbeams and they worked, this is the second time for this in a month. So what did we establish the issue could be? a relay or something else, and is it an easy fix(something I can do).

Thanks in advance.

 

[The_Roadie]

Swap black relays 45 & 46 for a test. It might be oxidation in the relay socket and simply replugging them will be the fix.

 

[smt 59]

Swap black relays 45 & 46 for a test. It might be oxidation in the relay socket and simply replugging them will be the fix.

Excellent Bill, I will give it a shot and give feedback on the results.

Thank you

S