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Amps for set of Marchals?

nfrntau

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Joined
Aug 15, 2004
Messages
1,020
Location
Rosharon, Texas
Apologize up front if I missed it, but I did a search and couldn't find it.
Does anyone know how many amps a set of Marchals pulls?
I'm in the process of installing my painless wiring harness and they recommended I use the in system aux relay for the fog lights. I wanted to know how many amps so I don't take a chance of overloading their relay. As a side note, I'm also installing relay's for the headlights. The tail lights, front blinkers and back-up lights are all led's so I'm not putting them on a relay.
Thanks
Bill
 

rvrtrash

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Joined
Apr 25, 2003
Messages
3,649
If you have an ohmmeter/ digital volt meter and measure the resistance between the positive wire and the ground, and then tell me whether you're going to wire them in series or parallel, I'll tell you how many amps you'll be drawing.

Steve
 

Mosesatm

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Jan 18, 2005
Messages
9,011
If you have an ohmmeter/ digital volt meter and measure the resistance between the positive wire and the ground, and then tell me whether you're going to wire them in series or parallel, I'll tell you how many amps you'll be drawing.

Steve

Ah yes. EE101.
 
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nfrntau

nfrntau

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Aug 15, 2004
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Location
Rosharon, Texas
With the ohms set at 200 I get a reading of 26.7 through the lamp and 0.3 when the two ends are held together.
I'm guessing I'll wire them parallel. With one relay I would have to wire them in parallel, wouldn't I?
 

rvrtrash

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Apr 25, 2003
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3,649
Parallel is the "normal" way to wire it, so that you have full power to each one and if one burns out the other will stay lit, but I try to never assume. Anyway, each lamp is about 1/2 amp, the circuit would draw 1 amp, and I always build circuits to take at least 50% more than their maximum rating. If their relay will take 1.5 to 2 amps, you're ok. Don't forget to run a circuit breaker of about the same size to protect the circuit.

Steve
 
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nfrntau

nfrntau

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Aug 15, 2004
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Location
Rosharon, Texas
Cool, Their relay is 20 amps and it has a 16 gauge wire feed to the item being powered. Should I keep the switch wires at 16 gauge also?
 

rvrtrash

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Apr 25, 2003
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3,649
If you're talking about the wires from the light switch to the relay, 18 gauge would be plenty, but there is nothing wrong with running heavier wire, and if you already have 16 gauge, I'd go ahead and use it. The only down sides are it's thicker so harder to route around stuff and more expensive.

Steve
 

XR7G428

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Dec 21, 2007
Messages
15
Location
Fountain Hills AZ
Caution: Wattage is equal to current times voltage. If you are running 60 watt bulbs, it would be 60 divided by 12 volts to give you 5 amps per lamp. In parallel, you would have 10 amps of current. I am pretty certain that the bulbs are at least 40 watts. Half an amp would indicate a power level of about 6 watts...

I think there might be a slight error in the measurement. If it were 2.67 ohms, then that would be the equivalent of 12 divided by 2.67 or 4.49 amps. This makes a lot more sense.

The point being, use the relay and adequate wire size for more current.
 

rvrtrash

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Apr 25, 2003
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That's correct. I'll go out tonight and measure my Lucas lights to see what they are. Since the Marchals were supposedly too bright, they should be close but a little less in resistance. Just goes to show the problems of troubleshooting over the internet.

Steve
 

rvrtrash

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Apr 25, 2003
Messages
3,649
Just an update. I'm going to have to look into this further. My lights are wired in parallel and measure .7 ohms each. This works out to almost 20 amps per light and 250 watts each if you assume a normal running voltage of 13.5 volts. In short, no way! Either my meter is flaking out or there is a resistor in the switch, something. I'll be gone all weekend but when I get back, I'll track it down and get it figured out.

Steve :confused:
 
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