I have 4 after market electric gauges and 1 aftermarket tachometer that need lighting. How many amps will be needed to light them up at night? If I draw the electricity from a power source, what thickness of wire should be used assuming the electric gauges have 16 ga. wires? Also, should a fuse be installed between the power source and the gauges? The Autometer web site does not have the specs I am looking for. Their tech support hasn't returned my email, either.
How many amps needed to light an electrical gauge?
- Thread starter sifan
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if each bulb is 5 watts, then 5 guages at 5 watts is 25 watts. 25 watts divided 12 volts = about 2 amps. 16 guage wire will certainly support 2 amps, it's rated up to 4 amps.
The tachometer uses a light bulb. The other 4 gauges are lighted by LED. Does LED use less light than a light bulb?
Yes, LEDs are much more efficient. So figure 5W/12V= ~0.5A.
If the source you're getting the extra 0.5A from is already fused, you may not need another fuse.
If the source you're getting the extra 0.5A from is already fused, you may not need another fuse.
Consider, however, whether the existing fuse is something that, if it were to blow while the vehicle is in operation, would cause a serious problem or inconvenience. (The fuse for the parking lights would fall into this category).
If so, either choose another fuse to tap power from or add a smaller fuse between the existing fuse and your gauges.
If you add a smaller fuse, that fuse will blow first if there's a problem with the gauges, keeping the existing fuse from blowing.
If so, either choose another fuse to tap power from or add a smaller fuse between the existing fuse and your gauges.
If you add a smaller fuse, that fuse will blow first if there's a problem with the gauges, keeping the existing fuse from blowing.
Just to confirm the other posters:
I recently did some current drain testing on bulbs and stuff, trying to chase down another problem. My guess is that a small tach bulb would draw very little current, probably less than 100mA. LEDs much less. 16 guage wire should be fine.
I recently did some current drain testing on bulbs and stuff, trying to chase down another problem. My guess is that a small tach bulb would draw very little current, probably less than 100mA. LEDs much less. 16 guage wire should be fine.
All very good suggestions and observations. 5W is awfully bright for an instrument light. Could also go way down on the wire gauge. I'd even say go as far down as you can manage according to your manual dexterity. 20-22awg should be fine as long as the connectors are made for the same gauge.
I like brianL's idea.
Consider mocking-up your tach at night with full +12v and compare it to your dash lights dimmed to how you like them. Consider splicing into the dimmed circuit if it's too bright; ashtrays usually have a worthless light. Lose the ashtray light and your current draw is the same compared to stock.
Read the directions for your LED lit gauges to see if they take well to dimming, or mock them up. You might decide to wire them seperately to a simple ignition hot source or the pre-dimming park lamp circuit.
Consider mocking-up your tach at night with full +12v and compare it to your dash lights dimmed to how you like them. Consider splicing into the dimmed circuit if it's too bright; ashtrays usually have a worthless light. Lose the ashtray light and your current draw is the same compared to stock.
Read the directions for your LED lit gauges to see if they take well to dimming, or mock them up. You might decide to wire them seperately to a simple ignition hot source or the pre-dimming park lamp circuit.
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