Packard Forum Index » V-8 (1955-56)

Hi - my headlamps are very dim - almost useless - when on low beam. They appear to be almost normal - adequate perhaps - on high beam. Any thoughts on what may be causing this?

Chris
56 Caribbean

Presuming the bulbs are correct and headlights aligned, the most common issue with a complaint of dim or non working Packard outside lights on most years is poor grounds. Headlight grounds are not usually as bothered with ground issues as parking and tail lights but can still have problems.

51-6 headlights get their ground via a wire in the cable from the socket in the bucket to the R & L fender terminal strips. The ground is under one of the strip to fender mounting screws. Rust, corrosion, and paint can do a job so the first suggestion would be to clean the ground terminal and screws and also make sure there is a good ground connection between the fenders and body.

Power to headlights is from an always on wire feeding other dash components. A spliced wire from that feed wire goes to the headlight switch. When the switch is on voltage then goes to the dimmer switch and then to lights. A bad connection on one of the wire terminals or a dirty or bad switch could be affecting the power supply to the bulbs. You might clean the terminals and also throw a meter between the ground screw and the Hi and Lo terminals at the right and left junction strips to verify there is a full 12.6 volts at least available to the strips. If not, then recheck grounds or clean or change a switch.

If you still see no difference one possible solution is add relays which would let you get power directly via a heavier wire. Eliminating the long run thru the headlight and dimmer switches via the stock smaller gauge wire often helps brightness a bit. Others have converted to halogen bulbs. If you go halogen bulbs check the wattage and amp requirement as it may be more than the stock lights and would need a relay to avoid damaging the old switches.

Thank you!

Chris, you did say that both high beams are OK, and both low beams appear to be dull (far less illumination). Based on that input:

Since the high and low beams of any one bulb share a common ground at the junction block the likelihood of a grounding problem is reduced. Likewise, since the high beams are functioning normally the circuits to and from the headlamp switch are also likely to be functioning correctly. The inference is circuit 15 (gray) at the dimmer switch is functioning normally, meaning it has the correct voltage when the headlight switch is ON. That leads us to the circuits between the dimmer switch and the low beam connections on the terminal blocks, or perhaps the low beam side of the dimmer switch itself.

I would confirm system voltage on circuit 15 (gray) at the dimmer switch, and then having a helper cycling the switch, the voltages at both circuit 7 (brown) and 8 (light green). Since circuit 8C (light green) powers the high beam indicator we can conclude the circuit 8 (light green) is the high beam (the good one). I don’t remember if the switch is removed from inside the car, or drops away from the cowl. In either way you might be able to conduct all of the tests solo, but it is always acceptable to have a granddaughter help.

We interpret the measured voltages by comparing the high and low beam circuits at the output of the dimmer switch. Both voltages should be about the same when powered, however if the voltage at the low beam is lower than the high beam the dimmer switch or connections would be suspect. If the voltage at the low beam is higher than the high beam voltage the problem is likely between the dimmer switch and the splice that bifurcates the low beam circuit to the left and right junction blocks.

All of this assumes a single point problem, not a simultaneous problem at two locations (like both junction blocks decide to quit working, or the connection at both bulbs somehow have higher than normal resistance). Multi-point failures do happen, but are less common than single point failures . . . assuming the first single point failure can be detected by the operator. Considering the environment the dimmer switch is subjected to I would jump to a conclusion that corrosion on the low beam side of the either the connection or the switch itself has resulted in a higher than normal resistance, and that resistance had reduced the voltage to the both low beams. It doesn’t take a lot of voltage drop to dull the bulb light output.

dp

I would pursue David's approach first as I would first expect some problem in the foot switch or the respective wire to the headlights, as that is the single common failure point of the system.

One thing I am surprised that no one mentioned yet is simply that headlights will dim with age. If the previous owner(s) only rarely used the high beams, it's possible you are just noticing old bulbs. Since few Packard owners drive much at dark, who knows how old they are.

The car benefited from a complete six figure restoration in 2007 - but even then - that was 16 years ago - so I'm going to try new headlights - as that's something I can tackle - if they're not the issue - i'll look a the dimmer switch next. I appreciate - your and everyone's input! Many many thanks.

Kif

HI David - many many thanks. I will definitely look at the dimmer switch on the floor. While the car was restored in 2007 - i'm guessing that it's gotten some grime on it in those 16 years - I would be very proud of myself if I could fix this -hahaha. (Give me a hammer and I'll break my thumb....not handy).

Kif

I would suggest the first step be simply to take some voltage readings to ground as Dave mentioned. Much easier than crawling under the car to clean or swap parts. For something like this, ultimately every part of the system is diagnosable and inspectable. Assuming the issue is not intermittent, then it is only a matter of measurement data to narrow down the problematic area.