LM headlight switch question

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nmunn
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LM headlight switch question

Post by nmunn »

Having issues with no voltage to my dash lights. Have verified there is no voltage coming through the green wire existing the switch.

Is there a way to test the switch itself?

Thanks in advance.




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66vairguy
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Re: LM headlight switch question

Post by 66vairguy »

The dash lights have a fuse in the fuse box. The shop manual has the wiring diagrams.
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bbodie52
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Re: LM headlight switch question

Post by bbodie52 »

I'm not sure about disassembling the light switch. If no voltage is coming from the terminal connected to the 20 DG wire, the fault could be an internal contact or the rheostat (dimmer) portion of the switch. The switch is probably more than 50 years old and a replacement is less than $20. You might just opt to replace the likely faulty/worn switch assembly.

:link: http://www.corvair.com/user-cgi/catalog ... N&page=84B
Image

Part number C1332: 64-69 HEADLIGHT SWITCH

Weight: 0 lbs 10 oz
Catalog Pages(s): 84B,R-24

Price: $ 16.95

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BACKGROUND INFO...

All of the instrument panel lights are fed by a single wiring harness distribution point behind the instrument panel. The wire color code is 20 GY (20 Gauge Gray). One possible fault location could be inside the 12-pin multi-connector behind the instrument panel. Even if the two plastic halves of the connector shell are tightly seated, a bent or corroded metal pin inside could be a disruption point.

In the Corsa instrument panel, the fuel gauge, tachometer, temperature gauge, clock, instrument illumination lights, turn signal indicator lights, and the high beam indicator light all rely on chassis ground for a ground return path. As shown in the illustration below, there is a single ground strap that provides a ground for all of these components in the instrument panel (necessary because the instrument panel itself is made of non-conductive plastic). This ground strap is secured to the dashboard metal frame (chassis ground) by a single screw. If that screw is loose, missing or corroded your entire instrument panel may not be properly grounded, which can cause the electric gauges and panel lights to malfunction or to only function intermittently. (Only the two engine warning lights are not dependent on an instrument panel ground).

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Reference Section: CORVAIR COMBINED WIRING SCHEMATIC DIAGRAMS

:link: viewtopic.php?f=225&t=12968

Tracing the circuit further back from the instrument panel multi-connector, the fuse block is the power source. It feeds the instrument panel lights and the heater control light. Check for a blown fuse. It is a 3A fuse labeled "PANEL LPS". The schematic diagram shows the power source for the fuse block to be the light switch, via a 20 DG (20 Gauge Dark Green) wire.


1965 Corsa Turbo, right?

The Corvair shop manuals divide the engine compartment, interior, and trunk wiring diagrams into separate sections that are displayed on separate pages. Sometimes it is easier to analyze a circuit if you can trace it end-to-end on the same page. The schematic is displayed below as an embedded image that can be enlarged by left-clicking it with your mouse for better viewing. If the cursor appears with a plus (+), the image can be clicked again to further enlarge it...


Image

Left-click the image to enlarge it for better viewing or "Pan & Scan". Click a second time for maximum enlargement...
1965 Corvair Corsa Full Schematic
1965 Corvair Corsa Full Schematic

1965-1969 Corvair - Instrument Cluster and Body Harness (CORRECTED)
1965-1969 Corvair - Instrument Cluster and Body Harness (CORRECTED)

1965 Corvair Fuse List and Fuse Block.jpg
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible
joelsplace
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Re: LM headlight switch question

Post by joelsplace »

If the running lights work then the internal contacts are working. All that is left is the rheostat but if you turn them all the way bright it bypasses the resistor. If the wiper is bad that would prevent them from working.
157 Corvairs, 5 Ultravans and counting
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nmunn
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LM headlight switch question

Post by nmunn »

Thank you, the green lead from the switch feeds the fuse box so it’s before the fuse I believe based on the diagrams I use.

Didn’t realize the switch was so cheap, I’ll order one.

Joelsplace, can you expand on the comment “if the wiper is bad that would prevent them from working”? I don’t see a dependency in the schematics on the wiper circuit.




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bbodie52
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Re: LM headlight switch question

Post by bbodie52 »

nmunn wrote:...can you expand on the comment “if the wiper is bad that would prevent them from working”? I don’t see a dependency in the schematics on the wiper circuit.
The rheostat in your light switch consists of a fixed wire coil resistor and a moving metal contact, or WIPER, that slides along the coil resistor to tap in at continuously variable points along the coil, which varies the resistance in the circuit to dim or brighten the instrument lights by changing the amount of electrical current flowing.

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Image
Brad Bodie
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Image 1966 Corvair Corsa Convertible
nmunn
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Re: LM headlight switch question

Post by nmunn »

Got it! Was thinking windshield wipers. Thank you all, new switch ordered.


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joelsplace
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Re: LM headlight switch question

Post by joelsplace »

Brad got what I was talking about. Sorry I wasn't clear.
157 Corvairs, 5 Ultravans and counting
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nmunn
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LM headlight switch question

Post by nmunn »

Interesting update. New switch came in and still no interior lights. If I jump power from the red terminal to the green terminal the lights work fine.


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bbodie52
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Re: LM headlight switch question

Post by bbodie52 »

You mean INTERIOR DASH LIGHTS?

1965 Light Switch Closeup.jpg
nmunn wrote: » Thu Jan 03, 2019 6:53 pm

Interesting update. New switch came in and still no interior lights. If I jump power from the red terminal to the green terminal the lights work fine.
If you jumper from 14 R to 20 DG you are applying direct unswitched and unfused BATTERY 12 V DC directly to the fuse block terminal that feeds the instrument panel lights. That would work — and verifies the circuit from the light switch to the instrument panel lights. But the lights would be on at full brightness (not dimmable) and on all the time until the battery is drained.

The internal light switch contacts should connect 14 R to 20 DG, but ONLY WHEN THE LIGHT SWITCH IS PULLED OUT TO RUNNING LIGHTS ON (halfway) or to HEADLIGHTS ON (pulled fully out). Voltage applied to 20 DG is routed via the rheostat, so it is both switched on in conjunction with the headlights or running lights, and dimmed according to the position of the dimming knob that controls the rheostat.

The 14 B/LBL wire supplies power to the headlight/dimmer switch to connect the headlights (normal or high beam option) to power from 14 R. 20 PPL (right next to the headlight wire 14 B/LBL) powers both front running lights when the switch knob is pulled to the halfway position. 20 BRN powers both rear taillights when the switch knob is pulled halfway or all the way out, so that the taillights come on in conjunction with either the front running lights OR the headlights.

When testing the instrument panel light output at 20 DG be sure that the light switch is pulled out to the halfway position or fully out to the headlight position, and be sure the dimmer position is not turned all the way down at CCW (rotate CW to brighten the instrument lights).
Brad Bodie
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nmunn
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Re: LM headlight switch question

Post by nmunn »

Brad, thank you. Yes correct jumping 14R to 20DG was just a test to ensure the interior light circuit worked from the plug forward. I replaced the switch thinking that was the issue. Hard to believe the new switch would be bad as well, but at this point the issue is narrowed down to the plug and/or the switch - I think.
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bbodie52
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Re: LM headlight switch question

Post by bbodie52 »

With a multimeter set as an ohmmeter to test for continuity, and the new switch unplugged, you should be able to see a connection between the switch terminal that normally connects to the 14 R wire, and the switch terminal that connects to the instrument lights (20 DG). The circuit switch should be closed when the switch knob is pulled halfway or all the way out (running lights or headlights). If your multimeter shows circuit continuity through the light switch terminals, you should measure different resistance settings (in ohms); as you rotate the dimmer knob. Continuity testing with an ohmmeter between the various switch terminals and the main input (14 R) should confirm all of the various switch settings, depending on the main light switch knob position.

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NOTE: I FOUND SOME OF THESE PICTURES ON THE WEB — NOT NECESSARILY CORVAIR BUT GM — SOME CORVAIR COLOR CODES MAY BE DIFFERENT.
Brad Bodie
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nmunn
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Re: LM headlight switch question

Post by nmunn »

Think I found it. The 20 B/OR wire was not attached. Didn't realize there was a separate switched power feed for the dash and tail lights.

Thank you all very much for the help.
ensys
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Re: LM headlight switch question

Post by ensys »

Mr.Bodie:

My apologies if this is a stupid/redundant question, but are the wiring diagrams excerpted above proprietary, or are they available for download in a larger file format? If so, where, please.

Thanks.
Keep 'em flying...

S.J.Szabo
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bbodie52
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Re: LM headlight switch question

Post by bbodie52 »

Which versions? The smaller images will enlarge for better viewing when you left-click them. A second click will enlarge them to maximum zoom to allow you to scroll around and see the details. All of the images started from the diagrams posted in the 1965 Chevrolet Corvair Chassis Shop Manual. I just did some combining and editing, and some corrections, cropping, etc. for various illustrative purposes. I used Microsoft PowerPoint for the editing changes and for combining three pages into one to create a continuous wiring schematic.

Image


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1965 Corvair Corsa Full Schematic (Rev. E)
1965 Corvair Corsa Full Schematic (Rev. E)

1965 Corvair Monza Full Schematic (Rev. E)
1965 Corvair Monza Full Schematic (Rev. E)

1965-1969 Corvair - Instrument Cluster and Body Harness (CORRECTED)
1965-1969 Corvair - Instrument Cluster and Body Harness (CORRECTED)
These and diagrams for other model years are available here...
CORVAIR COMBINED WIRING SCHEMATIC DIAGRAMS

:link: viewtopic.php?f=225&t=12968


If you let me know what you plan to do with them, I can try to provide a file copy in a format that might work for you. I could also convert them to Adobe Reader (.pdf) format.
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible
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