<VV> instrument lights

FrankDuVal corvairduval at cox.net
Thu Aug 17 21:26:21 EDT 2017

Close, except the resistor is connected to +12 volts, not ground! See 
1961 shop manual figure 8-72. The resistor element is in series with the 
instrument lamps. It is this way on most every GM car from way back into 
the 80s.

+12 Volts - variable resistor - lamps - ground.

The instrument lamps ground at each lamp.

Yes there is a switch also at the front of the headlamp switch that 
grounds the dome lamp circuit when the knob is rotated CCW. This is also 
the minimum resistance of the instrument lamps circuit. The whitish 
plastic cam in your picture activates this switch.

Frank DuVal

On 8/17/2017 4:20 PM, Doug Mackintosh via VirtualVairs wrote:
> The dimmer is a contact against a semicircular resistor consisting of coiled tiny cross-section wire. One end of the resistor is connected to ground. The instrument light power goes to the contact which is attached to the knob. As you rotate the knob it moves the contact along the resistor. At one extreme of the rotation most of the resistor is in the circuit (hence lots of resistance and dim lights); at the other extreme only a short piece of the resistor is in the circuit (hence low resistance and bright lights).
> I have had Corvairs where the contact between the contact and resistor was hit or miss due to corrosion. The resistor wire is also fairly delicate and can break, therefore breaking the circuit. I had one that worked intermittently for months. I got pretty good at wiggling the knob just right to get the lights to go on; sometimes pushing the knob inward slightly helped.
> Take the switch out and take a look (the resistor and contact are right at the front of the switch and clearly visible once you remove the switch). Test it with a continuity meter while you rotate the switch. I have been able to get one working in the past by some cleaning. Other times i had to replace the switch with a new used one.
> I made some notes and a diagram which I have attached for what it is worth.
> <<Date: Wed, 16 Aug 2017 16:57:17 -0400
> From: Byron LaMotte <bhlamotte at gmail.com>
> To: VirtualVair <virtualvairs at corvair.org>
> Subject: <VV> instrument lights
> Message-ID:
>      <CAN9cQMCS-u4Gr45bWVW=b4ayD+3b27KrXc+goqPvw=KjG-gXjQ at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
> Last night my instrument lights went out on my 1964 while fiddling with the
> dimmer on the light switch. I suspected a fuse but they look okay?
> Thoughts?
> -- 
> Byron (Brud) LaMotte
> 4501 World Farm Rd.
> Oxford, Md. 21654
> 410-924-1311 cell>>
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