Greetings All! I need to once again drink from the well of knowledge collectively know as the H.A.M.B. Beautiful day here so I thought I would take the coupe for a drive. Did some preliminary checks, oil, coolant, air pressure, lights. Everything was good until the light check. The driver’s side headlight is dim on both high and low beam. First thing was to swap headlamps. Trouble stayed on driver’s side. Also, the signal lamp is not as bright as the passenger side. Swapped signal bulbs, same. Checked for ground, solid. Checked for 12 volts both on high and low beam. Good Swapped headlamp plugs. Trouble stayed. Disconnected signal and parking wiring from harness, same. Ran a jumper from passenger side headlamp plug to driver’s side, same. Removed driver’s headlamp from socket, jumped from passenger headlamp terminals, still in socket, to bare terminals on driver’s headlamp. Both work fine. I’m stymied. Next step, Buckwheated? The signal flare is up! Be well and safe Jeff
You have a bad ground. Physically pull it apart and clean and check. Happens all the time when cars sit. Good luck.
Hi Dave I just checked again before responding. A good 100 point ground from engine to both. Thanks Jeff
Did you check the ground when the lamps were hooked up and turned on? Voltage loss due to resistance ONLY shows up when there's current flowing. Check the voltage ON the lamp, when turned on, not on the wires, connectors, sockets etc, measure on the actual lamp. You'll find that the voltage is low. Then you start to chase where you lose some of it.
You have high resistance in either the power or ground circuit connected to the dim lamp. Like G-son said, check the voltage at the bulb with the headlamp connected and turned on. With your voltmeter negative lead on a known good ground you should read within 0.2 volt of battery voltage at the lamp. (Example, if the battery voltage is 12.2 with the headlamps on, the voltage at the lamp should be at least 12.0.) If it reads less, you have high resistance in the power supply circuit to that lamp. Now connect the voltmeter positive lead to the ground lead at the lamp (lamp still connected and turned on, voltmeter negative lead still connected to a know good ground), the voltmeter should read 0.1 volt or less. If it reads more, you have high resistance in the ground side of the circuit.
Un hook the ground on that side and run a jumper wire to the other side ground. It looks like you have the ground wire to a bucket mount bolt. Just an FYI, stainless makes a crappy ground sometimes.
G-son Bingo! With the lamp plugged in, the voltage drops to 7. The hunt is on! I’ll report back when I find something. Thanks Jeff
When you found low voltage at the lamp, where were you measuring the voltage relative to? The chassis, negative battery cable, or some other point? If you were measuring the voltage across the light bulb housing and the contact, then you could still have a ground issue....
Well now, from one old timer to another, you have made me see the light my Brother! I was just about to start hunting through the wiring harness for a gremlin when I saw your post. Many thanks Jeff
It pays to double check, and check amount. A couple of times I did continuity tests, and seemed good, but wouldn't take a load. Only one or two strands in a connector were complete giving me a circuit, but couldn't carry the current. Re-did the connections, and back to normal. Glad you got it working.
Thanks to everyone for your troubleshooting tips! Couldn’t have done it without you. I hope this helps someone else down the line. Jeff
Bad grounds can do weird things; my son had an OT car that would die every time he stepped on the brakes. Turned out to be a bad ground in the trunk for the brake/tail lights that would, for some reason, backfeed into the car computer and shut it down.
I'm embarrassed to even admit to this story, years ago, a neighbour asked me to figure out why all the lights on the right side of his ford pickup didn't work. So....two frustrating, chase every wire I could, check every ground I could, days later, another neighbour, the dumbest one on the street comes by to see what I was doing. He says " did you check the bulbs?" Three guesses, first two don't count, turns out the bulbs had gone bad over time, I hadn't asked, or taken the time to check the bulbs, but I learned something that day.
Well trollst, I’ll see you that embarrassing story, and raise you one. After fixing the ground problem today and putting things back together, I did some reflecting. I wondered how the ground went bad from Autumn to now. I replayed all of the things I did to the car over the Winter and, eureka! It was me. I put a half hood on and had to remove the radiator shell to elongate the mounting holes so the I could move it forward 1/4”. I had to remove the headlights to pull the wires out of the shell. So, I sez to myself, while you have all of these washers and mounting bolts out, why don’t you clean them up and paint them? Therein lies the self inflicted loss of ground. When I put everything back together today, I used star washers to get a good bite and a good ground. I’m sorry for inviting you guys to my fire drill today. If there is a next time, hah! of course there will be, I’ll pause to reflect a bit before I call in air support. Thanks again everyone Be well and safe Jeff
12 years at a Buick dealership in the Midwest will teach you a few things. Bulbs, grounds, sockets, switches and pinched wiring. Got screwed by them all. Now how do I get rid of this nervous twitch?
Now that the lights are working great. And thats a pretty cool car your building,,,Find a set of front rims with the right off set**those are wrong, in the photos,if you were thinking about using them,they are bad scrub=set out too far/makes poor braking an steering,plus adds too darty from road bumps. Bring rim /tire in, with-in at least 1 in of norm} >king pin center line points to the road as ref. and that spot should be on or with in the tire contact patch with the road.< the way it is in photo,theres a fairly big gap from kingpin point on ground an tire patch=big scrub. Almost all the fins on drums should be covered by rim,if front is set up right. Yes there some guys driving cars like that,even say it drives great=No it dose not*,they don't know what a good driver feels like, an don't understand the engineering ,some defend there mistake,insted of leaarning. But its still a mistake that needs fixing. Hunt it up more,if what I said dose not seem to ring right in anyway. I owned my own speed shop for 40years,designed an built,an drove race cars all the time,plus hot rods.
Right you are Dana I made a mistake when I got those rims from a company that rhymes with “croaker”. It’s been bothering me ever since. I’ll hunt around for rims with the correct offset. Jeff
OK, I'll do it. The "rim" aka wheel hoop is what the tire is mounted on. The wheel center is what the "rim" is mounted on and can be mounted on in different locations giving you different backspacing. The "wheel" consists of the "rim" and the "wheel center" assembly.
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