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How to install a voltmeter?


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phamine 
Copper - Posts: 89
Copper spacespace
Joined: March 19, 2003
Location: United States
Posted: June 20, 2003 at 6:17 AM / IP Logged  
Should I run the wire for volts directly to the battery or to another constant 12 volts when the car is only on? Would there be a difference in accuracy?
hotrodelectric 
Copper - Posts: 112
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Joined: March 13, 2002
Location: United States
Posted: June 20, 2003 at 9:07 AM / IP Logged  
Easy hookup Phamine- you run the signal lead to any 12V "ignition" source. The best places are from the ignition switch or the fusebox. If you run it anywhere else, there will a small change in accuracy due to volt drop, but if the system is charging properly that should be no problem. Do not put it to a "battery" source- you'll wind up with a drain. If this is the only gauge you're installing, you should install a seperate fuse- 5A
should cover it- or tap it to the gauges fuse on the fusebox. If the gauge came with a fused lead, use that. If you're installing several, you can tie the ignition leads for all of them together including the voltmeter signal and use just one fuse, the size depending on the number of gauges.
phamine 
Copper - Posts: 89
Copper spacespace
Joined: March 19, 2003
Location: United States
Posted: June 20, 2003 at 2:39 PM / IP Logged  

Right now, I have 5 items running off one fuse from the fuse box. I'm using the radio fuse. 4 gauges that need power just for the backlight and one to turn on interior door lights that I installed which are not running off a relay. The are connected to a door switch ground and power coming off the radio fuse.

Sound like a good idea - I did not have my gauges fused. since I'm running 4 gauges just for the backlight, whats the average size fuse should I connect them to?

hotrodelectric 
Copper - Posts: 112
Copper spacespace
Joined: March 13, 2002
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Posted: June 20, 2003 at 9:45 PM / IP Logged  
How many watts are the bulbs? A little calculation- say each bulb is 10w (that by the way is pretty big for a dash lamp). Multiply the number of bulbs- in your case, 4, and you wind up with 40w. Divide by 12, and you wind up with roughly 3.3A. Add 10-15% for what's known as surge factor, and you're at about 3.8A. A 5A fuse should be safe for what you're after. If you want to run the gauge lighting and the power source for the gauges from this point, I would suggest a 10A. What gauges do you have?
phamine 
Copper - Posts: 89
Copper spacespace
Joined: March 19, 2003
Location: United States
Posted: June 30, 2003 at 1:41 PM / IP Logged  

Ran the guages great. I have Omori volt, water temp and oil pressure. I'm running it off my radio fuse via fuse tap. The radio is a fused 10amp. I would'nt need to run another fuse should I?

posted_image

http://images3.fotki.com/v29/photos/2/22469/39578/DCP_4196-vi.jpg

hotrodelectric 
Copper - Posts: 112
Copper spacespace
Joined: March 13, 2002
Location: United States
Posted: July 01, 2003 at 10:04 AM / IP Logged  
Well, give it a go, see what happens. The x factor here is your radio- I don't know what it takes to operate it. A safe guess is somewhere around 2-3 amps. I'll hazard a thought and say you're OK here, but if this does blow, do
NOT install a larger fuse- the circuit is protesting the larger load. You are tapping this from the radio side of the fuse? Also- what are some of those open spots in your block?
phamine 
Copper - Posts: 89
Copper spacespace
Joined: March 19, 2003
Location: United States
Posted: July 01, 2003 at 10:16 AM / IP Logged  

hotrodelectric wrote:
Well, give it a go, see what happens. The x factor here is your radio- I don't know what it takes to operate it. A safe guess is somewhere around 2-3 amps. I'll hazard a thought and say you're OK here, but if this does blow, do
NOT install a larger fuse- the circuit is protesting the larger load. You are tapping this from the radio side of the fuse? Also- what are some of those open spots in your block?

Yes, I'm tapping from the radio side of the fuse. Those slots are just empty slots that are not being used. I was considering wiring the open slots for the gauges but I do not know where to start.

hotrodelectric 
Copper - Posts: 112
Copper spacespace
Joined: March 13, 2002
Location: United States
Posted: July 02, 2003 at 12:13 AM / IP Logged  
Okelydokely. For the fuse slots- you can probe with a testlight and see if you get anything. Try it with the ignition off (indicating battery +) and the ignition on. See, on many cars the slots may not be fully loaded- most newer cars use a bussbar for distribution of power on the box. You can have a row of fuses with a couple of empties because the car didn't come with a particular option. The power is there because of the bussbar, but no output (accessory or 'cold' side) wire. The box looks vaguely familiar- Nissan, like a Sentra or a 200SX?
phamine 
Copper - Posts: 89
Copper spacespace
Joined: March 19, 2003
Location: United States
Posted: July 08, 2003 at 2:11 PM / IP Logged  
Used your idea of using a test light or voltmeter. It turned out one of those fuse slots is for heated seats, a canadian option. I rewired all my gauges to go to that particular fuse outlet which also needed a 10amp fuse if I had the option. The fuse panel is an import - its a honda prelude

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