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HEADLIGHT PROBLEM


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What could cause the drivers side low beam headlight to go out only when the light switch is pulled all the way out with the dimmer switch in the low beam position. The low beam works fine with the light switch in the next position inwards so the bulb must be good. The high beams work in all light switch positions. 

Edited by LAS VEGAS DAVE (see edit history)
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With the switch all the way out (fourth position), the driver's side should be on high beam, even with the dimmer switch in the low beam position.  The only light that switches in that mode is the passenger side.  In the third position, both lights will switch.  Also, the parking lights will go out when high beam is selected, and will be on when low beam is selected.

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4 hours ago, DonMicheletti said:

Read the manual - I believe that is the it is supposed to be,  I think they explain the logic too.

Don do you think the manual says the DRIVERS light is supposed to go completely out with the switch in the fourth position and the DIMMER on LOW BEAM?  Keep in mind that my car is a 38 not a 37.

 

 

Edited by LAS VEGAS DAVE (see edit history)
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7 hours ago, jeff said:

With the switch all the way out (fourth position), the driver's side should be on high beam, even with the dimmer switch in the low beam position.  The only light that switches in that mode is the passenger side.  In the third position, both lights will switch.  Also, the parking lights will go out when high beam is selected, and will be on when low beam is selected.

 

Jeff, you are right but I never noticed until you posted  that the parking lights go OUT if the light switch is in the fourth position and the high beams are on. They come back ON if the dimmer switch puts the LOW beams on. However in the high beam position my drivers side light goes OFF COMPLETELY if the light switch is in the fourth position. If the light switch is in the third position both high beams work as expected and also the low beams work as expected and both parking lights are always on.  To me it seems plausible that my drivers side light goes off if I hit the high beams in the fourth position so as not to bother the on coming traffic. It seems the fourth position should be used where you mostly use dim lights such as driving around town. Position number 3 is just like modern car lights with a normal high and low beams. Still I have a hard time thinking they would ever want one of the headlights to just shut off completely although when that happens the running light magically comes back on. Did they have drugs in 1938 as its possible the guy that designed the headlight circuit was on them.

 

Edited by LAS VEGAS DAVE (see edit history)
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Exactly as my '39 works - when in fourth position with high beam on the left bulb goes out.  With high beam off, fourth position lights are on.  High beam on at both lights in the third position.  I assume manual wording "asymmetrical" is what this is called....?

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Yesterday I found some thread here on the AACA that had a table of "what is on and what is off" in the various positions of the headlight switch for 1938 Buick. I have been searching for a half an hour now and cannot find it. If anyone knows where that thread is, please post.

 

I don't know what the source of the table was. I just remembered it was different than 1937, so did not post it in GaryW 's thread, so as not to muddy up the waters over there.

 

The main difference I remember is that the in position 3, both 1938  headlights beamed up and down with the floor switch.

 

I do not remember any position with one headlight out.

 

Does anyone have a wiring diagram for 1938? How about an owners manual that explains what should happen?

 

Edited by Bloo (see edit history)
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1 hour ago, jvelde said:

I assume manual wording "asymmetrical" is what this is called....?

 

Maybe, but in 1937 (and 1936) "asymetrical" meant Passenger side on low and drivers side on high. (They shine across each other, so the passenger side light is the one that shines into the oncoming lane.)

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2 hours ago, jvelde said:

Exactly as my '39 works - when in fourth position with high beam on the left bulb goes out.  With high beam off, fourth position lights are on.  High beam on at both lights in the third position.  I assume manual wording "asymmetrical" is what this is called....?

 

My car LIGHT CIRCUIT is EXACTLY like yours and it was made late in 1938 and the paint on the motor is also like 39! I am amazed at this circuit, when did they do away with this and return to the way cars headlights are normally wired? My car also has a different fuel pump FROM THE FACTORY with a vacuum assist on it with factory fuel lines. I found documentation showing that as an option. 

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1 hour ago, LAS VEGAS DAVE said:

when did they do away with this and return to the way cars headlights are normally wired?

 

That wasn't a standard until 1940 when sealed beams came out.  Before that, cars existed that simply dimmed but there were also cars that did not, and I have even seen documentation of something that had a five position switch. I don't remember what it was.

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Bloo,

 

I can't find where anyone has posted that on the forum. Attached is the 1937 Service Manual explanation of the Multibeam headlights for both 1937 and 1938. While the page numbers and a little bit of the formatting is different, the 1937 and 1938 Service Manual explanations are identical. This does not surprise me as they both use the same lenses, reflectors, trim rings, and most of the same internal headlight pod parts. There is some minor changes in the horizontal aiming assembly part numbers. The headlight pods themselves are different, which I think is mainly just different chrome trim. 

 

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5 hours ago, MCHinson said:

Bloo,

 

I can't find where anyone has posted that on the forum. Attached is the 1937 Service Manual explanation of the Multibeam headlights for both 1937 and 1938. While the page numbers and a little bit of the formatting is different, the 1937 and 1938 Service Manual explanations are identical. This does not surprise me as they both use the same lenses, reflectors, trim rings, and most of the same internal headlight pod parts. There is some minor changes in the horizontal aiming assembly part numbers. The headlight pods themselves are different, which I think is mainly just different chrome trim. 

 

Thank you for posting that!

 

The 1938 manual pages do clear up one point, the one that has been bothering me the most.

 

"The circuits of the control switch have been modified to enable switching from the upper beam to the fully depressed beam when in the third position as well as from the upper beam to the asymmetric passing beam when the switch is in the fourth position by operating the foot switch."

 

I don't see how they could have accomplished this without changing both the wiring harness and the switch.

 

 

 

 

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5 hours ago, Bloo said:

 

Thank you for posting that!

 

The 1938 manual pages do clear up one point, the one that has been bothering me the most.

 

"The circuits of the control switch have been modified to enable switching from the upper beam to the fully depressed beam when in the third position as well as from the upper beam to the asymmetric passing beam when the switch is in the fourth position by operating the foot switch."

 

I don't see how they could have accomplished this without changing both the wiring harness and the switch.

 

 

 

 

Bloo,

 

That same text also appears in the 1937 Service Manual. I am guessing that must describe a change from 1936 and they left the same text in the 1938 manual as well. Perhaps the word was still just getting out to people, or maybe they just did not want to bother to update the text since the circuit was identical to the 1937 circuit. The only curious item is that the 1938 switch has a different part number. Perhaps it came from a different supplier, or perhaps there was some minor improvement of some component. From the two service manuals, it appears that the 1937 switch and the 1938 switch operations are identical. 

 

With a quick glance I see a difference in the source of power for the dash lights and map lights being the only difference between the 1937 and 1938 wiring harness. Maybe you see something else.

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Here are the pages on headlights from the '39 Service Manual - as you will note, it references the '38 Service Manual for items that did not change, and discusses what did change.  Really convenient in trying to piece things together by bouncing between two manuals!

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Edited by jvelde
Made scans to show pages better. (see edit history)
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After reading those several times... I don't see it.

 

I don't see how it can be normal. I am still trying to get my head around how they made All-High/All-Low work in position 3. If I can ever figure that out, maybe we will have the answer. For the moment I suspect that that contact at the very end of the switch, pin 12, has failed. I suspect several people have the same failure.

 

It looks (for the moment) like all 37-39 should behave like the 1938 table above, with the possible exception of the fender lights. This guess could change...

 

 

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Dave, I don't see anything in either the '38 or '39 Service Manuals about the fourth position light going out on high beam.  It looks like to me, the right side should go to normal on high beam, which would indicate we have something wrong somewhere in the wiring or the dimmer switch.  Mine has been this way since I purchased it in 2010, and I just select third position for high beam and don't worry with it.  I tried correcting this issue when i installed a new wiring harness several years ago, and never found a solution. The inspection station I use lets me get by since I have high beam in both lamps in position three.

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I suspect there is something wrong with our lights also. I think you are right about the contacts  in the switch being the possible cause. We know the bulb and the contacts in the bulb socket are good as the light works properly in position 3 so whats left but the switch. Did you say you had a Rhode Island wiring harness?

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Jvelde, I have a YNZ wire loom made in California. According to their schematic their wire number 4 is not connected to my light switch. The post on the light switch that it is supposed to connect to becomes hot when position #4 is selected and the low beam switch is selected, otherwise it is not. I can not find the wire under my dash but I believe that is why my low beam goes out completely when I select low beams on the dimmer in the #4 position. Number 4 wire is at the fender board and is the low beam wire in the #3 position. I am going to live with it the way it is as I can use #3 position just like a later model car and #4 if I just want hi beams and no running lights. I tried a jumper at the fender board but although I can get the light to work in position 4 on low beams it makes it so that on position 2 the headlights are on with the parking lights when only the parking lights should be on. If I ever can find a #4 wire under my dash that is not hooked up I believe I could solve my problem but I can't find any wire not connected to something. The car had the loom installed when Lewis Jenkins owned the car by his mechanics at his Buick museum.

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Dave, 

I have not seen a schematic for the actual headlight switch contacts to know exactly how the headlight switch is supposed to work. I suspect that this obviously somewhat common problem is a common failure mode of the headlight switch itself. If you were to swap to a different headlight switch, I think it might solve this minor problem. 

 

In the near future, since I have the headlight switch out of my 1938 Century project, I will see if I can disassemble the switch and figure out exactly how it works to see if I can figure out what causes this failure.

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4 hours ago, MCHinson said:

Dave, 

I have not seen a schematic for the actual headlight switch contacts to know exactly how the headlight switch is supposed to work. I suspect that this obviously somewhat common problem is a common failure mode of the headlight switch itself. If you were to swap to a different headlight switch, I think it might solve this minor problem. 

 

In the near future, since I have the headlight switch out of my 1938 Century project, I will see if I can disassemble the switch and figure out exactly how it works to see if I can figure out what causes this failure.

 

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Dave, 

 

According to the 1938 Service Manual terminals 6 and 10 on the headlight switch are not supposed to have a wire attached to them. Are there three terminals without a wire on them on your car? If so, which other terminal does not have a wire attached to it? I still think your problem is likely to be an internal issue in the headlight switch.

 

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Just a quick reminder....  The headlight systems on these cars has one more confusing issue. Like Bloo said earlier, the headlights are effectivly reversed from left to right. The headlights are aimed to be "cross eyed". The drivers side light lights the right side of the road and the passenger side headlight lights to the drivers side of the road. Just tossing that out again as a reminder.  I also have a YNZ harness being installed in my 37 Roadmaster this winter. I had the harness custom altered to allow turn signals with the existing fender lights and brake lights. My car had sealed beam headlights fitted in the early 40's and a relay box added to handle the higher current required. I am fairly sure my headlight switch is in proper working order. When I get some free time I will collect it and map out the contact arrangement for all positions.

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5 hours ago, MCHinson said:

Dave, 

 

According to the 1938 Service Manual terminals 6 and 10 on the headlight switch are not supposed to have a wire attached to them. Are there three terminals without a wire on them on your car? If so, which other terminal does not have a wire attached to it? I still think your problem is likely to be an internal issue in the headlight switch.

 

 

MAC, on my switch there are 5 terminals on one side and 4 terminals on the other side not including the thermal fuse part. According to YNZ there should be the YNZ#4 wire hooked to the 3rd terminal back from the pull knob on the side of the switch with 5 terminals. The second terminal and the last terminal on the same side do not have wires to them on their diagram. Does this seem right to you?

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3 hours ago, 37_Roadmaster_C said:

Just a quick reminder....  The headlight systems on these cars has one more confusing issue. Like Bloo said earlier, the headlights are effectivly reversed from left to right. The headlights are aimed to be "cross eyed". The drivers side light lights the right side of the road and the passenger side headlight lights to the drivers side of the road. Just tossing that out again as a reminder.  I also have a YNZ harness being installed in my 37 Roadmaster this winter. I had the harness custom altered to allow turn signals with the existing fender lights and brake lights. My car had sealed beam headlights fitted in the early 40's and a relay box added to handle the higher current required. I am fairly sure my headlight switch is in proper working order. When I get some free time I will collect it and map out the contact arrangement for all positions.

 YNZ maks a great loom. Lewis Jenkins used them in all his Buicks.

 

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7 minutes ago, LAS VEGAS DAVE said:

 

MAC, on my switch there are 5 terminals on one side and 4 terminals on the other side not including the thermal fuse part. According to YNZ there should be the YNZ#4 wire hooked to the 3rd terminal back from the pull knob on the side of the switch with 5 terminals. The second terminal and the last terminal on the same side do not have wires to them on their diagram. Does this seem right to you?

 

If I understand you correctly, you are describing terminals number 6 & 10 which is should not have any wires connected to them. Please look at the switch part of the wiring diagram in the service manual, Section 12-42 on page number 270 of the 1938 service manual. 

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Thanks once again Matt, I see now on page 270 that the terminal that has nothing on it, not even the terminal screw, is terminal #9 on my light switch which they show a wire from it to the low beam in the drivers side headlight. So I am definitely missing that wire. I have no idea why. There is an extra wire from the new loom under my dash that has been snipped off kind of short and of course there is no number on it. I tried to put power to it with a jumper but the headlight did not light. It came out of the loom under the dash so I thought that I had found the wire but its been snipped for a reason and I will never know why. I could run my own wire but it would not be in the loom and it would stick out like a sore thumb. I hate that it doesn't work but I think I might just have to live with it. 

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Dave,

Please post a photo of the switch. The way you described it earlier would be terminal 6 and 10, not 9. Terminals 6 & 10 are not supposed to have any wires attached on a 1938 Buick headlight switch. I still think you have a headlight switch problem and not a missing wire. If that bulb works on position 3 and not on position 4, it would seem that the wire to that filament is not missing. 

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Matt, you are right that terminals 6 and 10 do not have anything on them. My terminals 6 and 10 also do not have anything on them but terminal 9 is supposed to have a wire on it that goes to the low beam according to the 38 shop manual and mine does not have that wire either. Terminal 9 only becomes hot in position 4 when the dimmer is on low beam. If i had the wire on terminal 9 like it shows in the shop manual leading to the fender terminal block everything would work----- I THINK.

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