High Beams Not Working

[LordFly]

Trying to pass a safety and I have no high beams. Nothing on the secondary side of the low beams either. All fuses seem to be ok, and I can hear the relay clicking behind me. Blue high beam symbol comes on on the dash, just no headlight changes. I've got 4 new bulbs coming this afternoon on the off chance its that, but I don't expect it is. Any suggestions on the most common cause?

[Dangermouse]

A bad fuse would seem to be the most obvious choice if all 4 filaments aren't lit.

Fuse "seems" to be OK, implies that you have only looked at it. Take it out and test it properly. Should be a 20A

[DMCMW Dave]

Or a bad relay or the switch itself.

[Elvis]

Blue bulb is in parallel to the high beams, therefore - if the wiring is stock - fuse, switch and relay should be OK.

Is there anything modified on your car ?
LEDs in the dash ?

With the schematic in your hand and a multimeter next to you - it should be easy to find the problem.

[Dangermouse]

I'm guessing that the switch is OK if he is hearing the relay click.


Actually, now that I am looking at the wiring diagram again, I see that all that is down-stream of the fuse are the 4 filaments as well as the Blue light on the dash. I presume that there is a junction below the dash somewhere where the Blue light is fed from, and the circuit is good up to that point.

[DMC5180]

High beam Feed is (BLUE/white) Check for a corroded pin connection at the (Main to Front harness connector) You must drop the Washer fluid tank to gain access to it.

Another remote possibility is that a mouse chewed the wire.

Your odds of having 4 bulbs out would be like winning the Lottery.

[Bitsyncmaster]

Like Elvis stated, if the blue indicator comes on your relay, fuse and switch are working. That leaves the wiring and or the bulbs. My bet is both bulbs are bad.

[SS Spoiler]

I'm continually amazed at the quality of information and speed of everyone pitching in to help each other. Is this true on all exotic car sites, or are we the exception?

[Dangermouse]

We have a distinct advantage in that we have many people called Dave or David.

[OverlandMan]

Like Elvis stated, if the blue indicator comes on your relay, fuse and switch are working. That leaves the wiring and or the bulbs. My bet is both bulbs are bad.

I have the same problem on my car as the OP described. I replaced all 4 headlamps. The low-beams come on but no high beams. Switch works, relay works, indicator comes on cluster. I'm betting the issue is on the front harness where the church connecters "mate". I had a burned up pin/plug for one of my cooling fans already in that same spot. Just haven't had the time to get back into the wiring in that spot again.

17713

[David T]

It is easy enough to check the filaments with a meter. It is very possible for all of the high beam filaments to be burnt out. While checking the filaments you can also check for voltage on the low and high beam connectors and if the grounds are intact.
David Teitelbaum

[LordFly]

A lot of good guess in there, but after finding the problem, I can't blame anyone for NOT getting this answer:

The PO had the bulbs backwards :shocked: Yes, 3 pronged low beam plugged into the 2 prong high beam socket, and 2 pronged high beam plugged into the 3 prong low beam socket. Not to mention most of my headlight bezels are held in with wood screws :thumbdown: I'm glad I took this car away from the PO before he did any more "work" on the car. It's ok baby, I got you now, I'll take good care of you :kisses:

[Dangermouse]

That was going to be my second guess :)

[Bitsyncmaster]

By the way, the headlights have two ground wires running from the front harness to the relay compartment. Don't know why they did that other than a plan to make a blown headlight indicator. But I changed my headlights to use the frame ground. That gave me two extra wires up front to use for other things (my side light circuit). It also eliminates two of those pins that could fail on those "church" connectors.

[David T]

There is no way we can guess at all of the possible permutations and mistakes DPO's can make. We base our best guess on the assumption that it actually worked previously. Obviously that was not so in this case. We rarely have all of the history on which to base our guesses. The methodology was good though. Once you removed the headlights to check grounds and filaments you discovered the real problem.
David Teitelbaum