power fro a cigarette lighter.

[fishingstar]

I'm trying to power a camera for the back of my camper. I was going to use the cigarette lighter for power on the monitor. the plug in I'm using shows 12 volts but after I hook the monitor and receiver to it drops to 2.3 volts. I don't under stand why this is happening.

Is there anybody that can explain this to me.

Dan

[jentz]

I never knew this but on some newer models cars and trucks they add a cigerette lighter plug for computers and cellphone chargers. Our ford has two cig plugs. one at 12V for the lighter (which isn't there) and another cig plug that in the cars manual is lower volts for what I stated above.

Right when I saw two,I thought OK we'll both start smokin! We won't argue over who gets the lighter first!

[delcecchi]

This the lighter socket in the car? What kind of car/truck?

[LMITOUT]

Must be a transformer in the cig lighter plugin for the monitor. Not uncommon. Probably says 12V just as an indication of what the input voltage should be.

[jentz]

This the lighter socket in the car? What kind of car/truck?

Its a Ford taurus.The cig lighter is next to the ash tray,Just below it is a empty space like a cd storage without dividers thats where the second lighter plug is located and states its for charging and computer.

2003 Tarurus the owners manual is found online easily

[fishingstar]

It is a 02 gmc sierra. I plugged it in I got 12v with a multi meter. The plugin is not part of the monitor.

[Whoaru99]

It's not clear where you're measuring 12V before and 2.3V after you connect the gear.

A cig lighter socket should be able to supply many amps. I'd say at least 10, if not 20, and I can't see a camera system being more than a couple amps.

Typically if the voltage drops under load as significantly as reported it's indicative of a high resistance/poor connection on the hot or ground side. The multimeter reads full 12V because just the meter itself presents, for all intents and purposes in this type of circuit, no load on the circuit. No load = no voltage drop.

[fishingstar]

I'm testing the power at the end of the two wires of the cig adapter and I get 12v. When I hook up the monitor and receiver they both have 24 ga wire all three have there wire twisted together and taped (this is a temporary connection). I get the system to work if I hook up to my trolling motor.

I would like to use the cig for a power source for convenience only using when pulling the camper.

[delcecchi]

Something hooked up wrong, or it wants AC

[Jeremy airjer W]

Lets all get on the same page with what we are calling what...

The 12 volt plug, which is this

The twelve volt socket, which is this

Where did you get the twelve volt plug?

With a load on the circuit what do you have for voltage at the socket (you will have to do some digging to get at the connections on the backside)?

If there is twelve volts at the socket with load and there is only 2.3 volts coming out of the plug than the plug is the problem. Possibly it is meant for a device that requires little voltage and has some internal resistors to drop the voltage.

You could confirm this by using a couple of jumper wires from the battery. The positive will go to the center of the plug. The negative will go to one of the two side tangs. If you still have less than 3 volts its the plug.

[Jeremy airjer W]

Something hooked up wrong, or it wants AC

[fishingstar]

I'm getting 12v from the 12 volt plug when it is plugged in to the truck at the end of the wires.

I got the plug from a old device that didn't work any more. It gave me 12v so I thought it would work.

[Whoaru99]

If you're measuring the output from the cig lighter plug and the voltage drops when you connect the camera, either there is a connection problem upstream in the vehicle, or in the plug you're using, or as Jeremy mentioned, possibly resistors or something else causing voltage drop through the plug.

Since it doesn't work for what you want, can you take it apart to see what's inside?

If it's from an old GPS or phone, yes, those often do have voltage regulators or voltage dividers or dropping resistors to reduce the output.

[fishingstar]

sounds like I should get the right plug instead of one from a portable dvd player. Or power from the fuse box with a weather pack connector.

Thanks for the help

Dan

[Jeremy airjer W]

To answer you question as to why you are only seeing 2.3 volts.

In the diagram below 1,2,3, and 4 are the test points. The resistance could be anything from corrosion to a loose or burnt up connection that should not be there. the load is any device you are trying to power up.

If the switch is open we will have 12 volts and 1, 2, and 3. If we close the switch we will have 12 volts at 1. 2 will show less volts depending on the amount of resistance there is and 3 will show 0 volts. The resistance in the circuit will cause a voltage drop but only when the circuit is completed by the switch. The load will use or drop the rest of the voltage again only when the switch is closed.

If we use your scenario you would see 12 volts at 1 and 2.3 volts at 2.

If you where to put your black test lead on 1 and your red test lead on 2 you would see 9+ volts (somebody correct me if I am wrong). Your are measuring the voltage drop at this point and now you know there is extra unwanted resistance in the circuit. If you put you black lead on the battery positive and your red lead on 1 you would see 0 volts because there is no resistance in that part of the circuit.

If the resistance were not there and you where to put your black test lead on 1 and your red test lead on 2 you would see 0 volts. If you were to put the black lead on number 2 and the red on 3 you would see 12 volts (the load is using the voltage)

Does that help?

[fishingstar]

I did test the wires to make sure I got the right wire. I put my red lead at the point of the plug and the black lead on a the power wire and got all 0's witch is no resistance.

[Whoaru99]

All zeros would indicate very low resistance, as in a good connection, at least between those two points of measurement.

0 = short circuit/good contact (what you see when you hold the two probes together)

0L (or something to that effect) = open circuit (what you seen when the two probes are separated)

Do the same thing from the ground contact of the plug to the ground wire.

Then also (on the plug) measure resistance between the tip and ground contact, then between the power and ground wires.

Bear in mind always measure resistance with the power off/disconnected...