Electrical gremlins in dashboard

[markdt]

I took the dash off to try to figure out why the tachometer wasn't working. The post for the brown wire was grounding to the case causing the stall when I tried to connect it to the coil. The red plastic washer wasn't insulating for some reason and I had continuity between the threaded post and the tach case. I added an insulated washer and reconnected the brown wire. I could now connect the coil without it stalling but still I get no reading from the tach. I am getting 12 volts to the positive connection. I tried connecting an independent wire from brown post to coil, but that didn't work either. The tach needle will bounce up if the tach is tapped on so it seems the spring is working.

I'm willing to pull the tach out if can anyone share a step by step bench testing process. The only tachs I could find for sale were listed with no guarantee that they were operable.

Now the Gremlins. The temp gauge and clock work as do the speedo lights and warning lights. Interestingly though, the tach lights don't work and the right turn indicator light stays on whenever the lights are on. The signal indicator works, but the dash light doesn't blink or go off.

Could this be related. I double checked that the ground strap is present and is tightly screwed against the dash.

Finally, I did see an extra connector behind the dash with pink and green wires that looked similar to the connector that is already on the speedo. The wiring was replaced by the PO. Might this an extra for something that I don't have or a different configuration.

Thanks in advance.

[bbodie52]

1965 Corvair Corsa Full Schematic

I took the dash off to try to figure out why the tachometer wasn't working. The post for the brown wire was grounding to the case causing the stall when I tried to connect it to the coil. The red plastic washer wasn't insulating for some reason and I had continuity between the threaded post and the tach case...I am getting 12 volts to the positive connection...The tach needle will bounce up if the tach is tapped on so it seems the spring is working...

THIS WOULD SEEM TO INDICATE A DEAD SHORT THROUGH THE INTERNAL CIRCUIT BOARD TO GROUND. IT IS NOT THAT THE POST IS NOT INSULATED FROM THE TACHOMETER METAL HOUSING — IT IS A PROBLEM WITH THE COMPONENTS ON THE TACHOMETER CIRCUIT BOARD. The circuit should appear as a high impedance input that reads the impulses that occur as the ignition points open and close — switching the coil on and off as the electrical current from the positive terminal passes through the coil primary winding and then passes out through the negative terminal and to chassis ground when the points are closed.



Description. Here is a simple circuit that can be used as a tachometer. The circuit is basically a frequency to current converter which converts the incoming signal into a proportional current to drive the meter. The deflection on the meter will be proportional to the frequency (count) of the incoming signal pulses from the coil negative terminal. The input on the is connected to the base of the Transistor Q1, which switches the current fed to the meter M1 on the right. More pulses from the points causes more current to flow through the transistor, which increases the meter deflection which indicates a higher engine speed. The transistor has a high impedance input so essentially no current can flow from the coil negative connection through the tachometer to ground. A faulty component to the left of transistor Q1, such as a shorted diode, could be the cause of your tachometer failure. NOTE: THIS SCHEMATIC IS NOT THE ACTUAL CORVAIR TACHOMETER SCHEMATIC. IT IS ONLY A REPRESENTATIVE DIAGRAM OF A TYPICAL TACHOMETER CIRCUIT.

Since you are seeing a short to ground from the tachometer input terminal, there is apparently a failure of the transistor input circuit that is now shorted to ground, which kills your engine when you connect the coil negative terminal to the defective tachometer. Your notes indicate that 12 VDC is available on the other post to power the tachometer circuit, and the tachometer case is grounded to complete the power circuit.

http://dandmrestoration.com/tachometer-repair/

D&M Restoration rebuilds and repairs almost any antique, classic or vintage car tachometer to its stock/ original condition, or we can convert a mechanical tachometer to an electric tachometer while keeping the original appearance. We have designed our own circuit boards for upgrading and repairing many of the electric tachometers. When we rebuild your tachometer we upgrade it so it will work with a H.E.I. (High Energy Ignition) system. When we install the new meter movement on bi-coil tachometers, we can also replace the meter movement as well with a 4 pole one, which makes it quicker and more responsive. This new system is the latest in tachometer technology and is MORE ACCURATE than the original and is more RESPONSIVE!

Now the Gremlins. The temp gauge and clock work as do the speedo lights and warning lights. Interestingly though, the tach lights don't work and the right turn indicator light stays on whenever the lights are on. The signal indicator works, but the dash light doesn't blink or go off.

Could this be related. I double checked that the ground strap is present and is tightly screwed against the dash.

The power and ground for each individual tachometer illumination bulb socket needs to be checked with a multimeter, and each bulb needs to be checked to see if it is functional.

Both the right and left turn signal circuits use the same fuse block power source and flasher unit to power each side. Moving the turn signal lever changes the switching to connect the left or right turn signal circuit (front bulb (1157), instrument panel directional indicator bulb (1445), and rear bulb (1157)) to the fuse block flasher switching on/off voltage output. The flasher will only function properly as an on/off switch if it is fully loaded by all three bulbs. If one or more bulbs is burned out or not installed or grounded properly, the total current flow will be reduced and the flasher will hang up and not switch at all, or it may flash at a faster rate. The proper 3-bulb load controls the total electrical current draw, which regulates the internal on/off switching rate of the flasher.



How Turn Signals Work
https://auto.howstuffworks.com/turn-signal2.htm

1965 Corvair Chassis Electrical - Bulb Specs

Corsa Instrument Panel (Rear)

[markdt]

Thank you for the link to the tachometer repair. I will check the bulbs and lighting with the multimeter.

Regarding the turn signals: I didn't make myself clear. The turn signal switch seems to work correctly in that the front and back signal bulbs and the left dash indicator bulb all work as expected. The the right dash indicator bulb either does not light at all if the headlight switch is off or receives constant power if on and stays lit at all times. Yet, the right front and rear indicator bulbs work as expected and blink at the normal rate. The right dash bulb does not blink when the right front and rear bulbs blink, nor does it go out when the left bulbs are flashing.

I need to track down why the right dash indicator bulb is getting constant power when the headlight switch is activated

[bbodie52]

So the right turn signal indicator bulb is off when the headlights are off, and is on continuously when the headlights are on. With the headlights on, does the right indicator bulb go off when you switch the headlights to low beam? If it does, it sounds like your right indicator socket is wired to the high beam/low beam indicator bulb. The wire for the right turn signal indicator may not be connected at all.

RH Turn Signal = 20 DBL
LH Turn Signal = 20 B/LBL

High Beam Indicator = 20 B/LG


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1965 Corvair Corsa Full Schematic

CORVAIR COMBINED WIRING SCHEMATIC DIAGRAMS
viewtopic.php?f=225&t=12968

[markdt]

No, the right dash turn indicator stays the same whether on high or low. It does dim using the headlight potentiometer that controls the dash lights.

Currently about 115 degrees in my garage, so I'll wait till tomorrow morning to continue trying to exorcise the demons. Have to love a Phoenix summer.

[bbodie52]

The light socket could simply be wired as an instrument illumination bulb, since it only comes on with the light switch and dims like an instrument light. Somehow you ended up with a gauge illumination bulb inserted into the turn signal socket!