Looking for assistance with aftermarket gauges

[wgFlatliner]

Alright, first off, the gauges i have are from the Autometer Cobalt series. I have the wideband, mechanical boost/vacuum, and electric oil pressure.

The electric gauges have their accompanying wiring harnesses with them.

My question has to do with hooking up the wires the correct way.

Lighting.
The wideband doesn't have illumination so this would only involve two of the gauges.

I was thinking of hooking up the power wire from the lighting dimmer switch from the dash (the knob you can twist to brighten or dim the lighting on the dash) to the first gauge's + terminal, then a wire from the - on that gauge to the + on the other gauge, then the - on THAT gauge to the chassis ground. would this work?

[shorod]

How do the gauge instructions say to wire them up? Is the positive wire supposed to go to a dimable power source? By wiring the gauges in series like you propose, each gauge in this case would only be seeing half the total voltage, meaning if the guages use incandescent bulbs, they will be quite dim. If the gauges are pretty new, they likely use LED illumination with currently limiting resistors. If you half the voltage to each, you probably won't notice any illumination. Most likely, you should parallel the illumination inputs of each of the gauges. But again, check your owner's manual for the gauges to see how they are supposed to be connected.

-Rod

[wgFlatliner]

Originally Posted by shorod

How do the gauge instructions say to wire them up? Is the positive wire supposed to go to a dimable power source? By wiring the gauges in series like you propose, each gauge in this case would only be seeing half the total voltage, meaning if the guages use incandescent bulbs, they will be quite dim. If the gauges are pretty new, they likely use LED illumination with currently limiting resistors. If you half the voltage to each, you probably won't notice any illumination. Most likely, you should parallel the illumination inputs of each of the gauges. But again, check your owner's manual for the gauges to see how they are supposed to be connected.

-Rod

This is the second time i've heard the phrase to parallel the gauges.. can you explain the term parallel? The gauges are brand new, LED illumination. The instructions don't say whether or not it can go to a dimming source. The instructions only reference the lighting wire as "12v dash lighting" which i would assume all lighting to the dash is 12v, dimming or not.

[shorod]

Okay, if the + wire you are referring to is the "12V dash lighting" wire in the instructions, you should be fine to use the instrumentation illumination wire from the dimmer. There may be some rare cases where the instrumentation illumination wire is a 5V or other level, but I'm not aware of any particular vehicles where that's the case.

To parallel the guages you'd run the + 12V dash illumination wire of each gauge to the dimmer switch output and the - ground wire from each gauge to ground. This is a parallel configuration. As you can probably understand from drawing this up, both gauges would receive equal dash illumination voltage and they would be completely independent of one another.

If you went with the series configuration you proposed above, you'd basically end up with a voltage divider circuit. The dash illumination voltage would only be across both gauges wired in series. Assuming the current consumption of both gauges was identical, each gauge would only see half of the dash illumination voltage. Plus, if the illumination circuit of one of the gauges failed open, both would stop working. I'm not sure of your religion, age or experience, but if you've ever experienced a string of Christmas lights with a loose bulb, when that one bulb goes open circuit, the whole string of lights goes out. That is a series configuration.

-Rod

[wgFlatliner]

Originally Posted by shorod

Okay, if the + wire you are referring to is the "12V dash lighting" wire in the instructions, you should be fine to use the instrumentation illumination wire from the dimmer. There may be some rare cases where the instrumentation illumination wire is a 5V or other level, but I'm not aware of any particular vehicles where that's the case.

To parallel the guages you'd run the + 12V dash illumination wire of each gauge to the dimmer switch output and the - ground wire from each gauge to ground. This is a parallel configuration. As you can probably understand from drawing this up, both gauges would receive equal dash illumination voltage and they would be completely independent of one another.

If you went with the series configuration you proposed above, you'd basically end up with a voltage divider circuit. The dash illumination voltage would only be across both gauges wired in series. Assuming the current consumption of both gauges was identical, each gauge would only see half of the dash illumination voltage. Plus, if the illumination circuit of one of the gauges failed open, both would stop working. I'm not sure of your religion, age or experience, but if you've ever experienced a string of Christmas lights with a loose bulb, when that one bulb goes open circuit, the whole string of lights goes out. That is a series configuration.

-Rod

awesome, that makes perfect sense.

thanks!

btw, the SHO rocks