Hi guys,

Looking for some opinions and guidance on an issue that recently popped up.

I was in route to get my annual MA state inspection sticker this past week. Did my usual check, everything was operating normally; i even remembered to put a front license plate on this time .

Unfortunately, by the time I made it to the inspection station, the drivers side high beam was out. The passenger side high beam was functioning as normal. Seemed simple enough, but this thing has had me stumped all weekend.

Here's what i've tested thus far -

1. Confirmed it was not a problem with the bulb itself.
Swapped passenger and driver side lamps; drivers side bulb worked fine in passenger socket. passenger side bulb did not illuminate in drivers socket.

2. Confirmed normal operation of the high beam switch.
The switch operates the passenger side high beam as normal. The switch activates high and low as normal.

3. Confirmed the drivers side high beam socket had power.
Confirmed it is getting power with my test light (test light lit normal and bright). Haven't tested with my multi meter, but that is my next step. Confirmed power to the drivers side high beam socket when the switch was in high beam mode. Confirmed no power to the drivers side high beam socket when the switch was in low beam mode.

4. Checked the grounds for any obvious signs.
Checked grounds from high beam socket to head lamp socket and from head lamp socket to ground source.

5. Ran ground from a test wire to the driver side high beam.
I ran an independent ground wire to the drivers side high beam, while using the normally supplied power source to the high beam, and no luck. Confirmed ground source, tried again, no luck.

So, here is where i'm stuck guys. I'm going to confirm voltage numbers at the drivers side high beam socket with my multi meter.

Besides that, am I missing or overlooking anything here?

 

An electrical item receiving VOLTAGE can be found with a test light. But, knowing that the same item can carry necessary CURRENT can not be determined with a test light.

Inspect the 'ground' connection and wiring on the socket for that 'problem' lamp position. Make an ohmmeter check from that terminal in the socket to a CLEAN grounding point. It should read almost ZERO ohms. If you have some resistance there....or there is no connection, you've found your problem.

 

Thanks. Quick update...I had a few minutes to get over to the garage this evening. I tested both the ground wire (ohms) and power wire (volts). Ohms read next to zero and volts read 11.9. I tested the passenger side too just for comparison sake and the numbers came out the same.

So, I have ~12V power and ~zero resistance.

Any guidance or input is appreciated!

 

Since you tried changing bulbs and both work in passenger side I would verify the socket and clean and make sure good contact. May need to take clip out and squeeze to ensure good connection. Only other item that comes to mind is if the 12 volts you read will carry current. You could jumper the ground to bulb and put ammeter is series on higher current scale and see if you can draw current. Maybe the 12 volt wire is worn somewhere and onlt few strands holding together. Lights draw quite a bit probably 5 amps so may read voltage without load but not carry current.
Good Luck

 

Rookie advice: The contacts inside the socket may be collapsed/corroded/glazed-over and do not touch the high beam blade on the back of the bulb. I think the contacts inside the socket can be removed for cleaning and for "re-arching" to make solid contact with the blades on the rear of the bulb.

 

Hmmm.... Since your low beam filament in that lamp works using the same grounding pin, the ground is not likely your problem. Wish I had thought about that earlier.

Can you rig up a way to insert the bulb into the socket, but have the positive voltmeter lead also touching the power pin for the hi beam (and negative going to a good ground location). Then turn on the lamp (it still should not light...or be extremely dim) and read the voltage. If it is significantly lower, there is some corroded contact or connection somewhere in the hi-beam power to that socket. And since the right side works OK, the fault will NOT be with any component that passes power to BOTH bulbs....it must be a separate contact/terminal/connection.

 

Your Low beam bulb is duel element so inspect the crimp connectors at both right side bulbs.
The High beam element of Low beam bulb jumpers over to the single element of the High beam bulb.
I had the same problem with my Low beam passenger side. I removed the series 59 crimp connector from the housing and found a bad crimp and wire was almost broken on the jumper side wire of the duel element bulb.
If you need to replace that crimp connector (the duel jumper wire crimp) the part number is GM #2973215. If you have a bad single wire crimp the number is GM #2973216
These are not your standard 1/4" series 56 connector they are 5/16" series 59.
My bad crimp and a practice crimp

 

Interesting possibility....

 

Thanks guys. This gives me good direction to continue diagnosing the problem. I'll report back once i'm able to dig in.

 

Alright guys, back with another quick update based on the advice you have provided...

I first followed Henrikse and Doorgunner's advice and removed the contacts from within the socket. They looked good, but I cleaned them up to be safe.

I then followed 7T1Vette's advice and inserted the bulb into the socket, with my tester on the positive lead, while touching the power pin for the hi beam (and negative going to a good ground location). As soon as the positive lead touched the bulb contact, the volt reading dropped from 11.9 to 0. This tells me that there is a corroded contact or bad connection going to the high beam socket and that the initial 12Vs at the jumper wire is not carrying current.

Finally, following what bmotojoe mentioned above, I inspected the jumper crimps and did notice one crimp (the duel jumper wire crimp) that didn't look great, despite the clip looking fine.

Oh, I also went ahead and ran a 12V hot wire to the high beam, while using the properly supplied ground source just to 100% rule out a ground issue (despite the ~0 ohms reading already verifying this). The beam lit up no problem, confirming a good ground source to the socket.

I ordered the new GM clips and my next plan of attack is to replace the duel jumper wire crimp, as well as the 6 inch jumper wire itself.

Any feedback or further guidance is always welcome.

- Chris

 

Sounds good. It's nice to have someone willing to try the suggestions provided to them. I'm sure you are on the way to getting it back up and running like you expect.

 

The jumper wire:
Using Mr. Willcox 1979 line diagram it looks like that jumper is Lt.Green and 0.8, I think that converts to like 18 gauge, you can certainly use 16 if you want and it may actually give you a tighter crimp on both of your repair ends.
You want to use either type SXL or GXL automotive wire, both have the same heat ranges (-51C to 125C) and used in these old cars. SXL is Cross-linked in design and the insulation is just a little thicker.
Personally I have been using GXL only because the insulation is a hair thinner. Just not as bulky when you bundle.
Let me know if your having trouble locating SXL or GXL wire.

 

Let there be light! The culprit: bad Jumper wire/crimp.

Back in action just in time for the weekend! Thanks for the great advice you all provided.

Cheers,
Chris