Voltage question

[ram250098]

I have been sorting out some wiring gremlins in my 73 Charger. I disconnected the negitive lead from the battery leaving the postive hooked up. I then put my volt meter leads from the negative post of the battery and the other to a good ground and I read 4 volts. What gives?/ a short some where?
AL

 

[lewtot184]

i'm not an electrical expert but if there are 12volts in the battery (have you checked this?) and your only getting 4 volts at the ground, then its not a good ground. go back thru all your ground(s) and make sure they're clean and no paint.

 

[bigmanjbmopar]

Switch the meter to current and tells us what you read.

 

[70rr-brian]

Your test is essentially invalid. Without the multimeter being set to measure current as bigman indicated then there is no way for voltage to be measured in your scenario. The reason is...measuring voltage requires a path from the positive side of the battery to the negative to complete the circuit. In your test...you are simply measuring voltage. (I am assuming your probes are connected to V(Ω)&COM) This is to say that there is nothing to complete the connection from the positive to the negative side of the battery to properly measure voltage doing what you are doing. In your scenario, the only way for you to get a proper reading would be for you to move your red probe from (Ω) to (A) thereby allowing your multimeter to be a pass thru for electrons. The multimeter would then act like the disconnected negative battery cable and should then be able to read the voltage. (technically current)

Why you are reading anything at all I simply don't know. I do know that in simple voltage reading mode (probes on V(Ω)&COM)) there is no connection for electrons to flow from one side of the battery to the other using your testing method.

 

[ram250098]

I was tracing some wires that day and had my test light hooked to the ground on the battery. I put the test light down on the engine and noticed the light came on very dim...I thought that was odd which is why I tested for voltage. I only have a volt meter..maybe I should spring for a multi meter one of these day's.
Thanks guy's
AL

 

[bigmanjbmopar]

I was tracing some wires that day and had my test light hooked to the ground on the battery. I put the test light down on the engine and noticed the light came on very dim...I thought that was odd which is why I tested for voltage. I only have a volt meter..maybe I should spring for a multi meter one of these day's.
Thanks guy's
AL

Yes get a multi meter, reading volts, ohms and current is essential to correctly and easily finding problems. Remembering this one fact......GROUNDS yes without good grounds for the components it will not work. I will say it again GROUNDS. Every electrical part on the car has to have a GOOD GROUND to work. Knock that possibility out and go from there.

You can always use the hand method too - lick you fingers and grab the positive post and touch what ever you think is giving you a problem, if you get shocked you know you have voltage there......J/K please do not do that lol ccasion14:

 

[ram250098]

LOL Thanks for the link you fingers test...that is one thing I do over kill on is grounds..so much so I tend to use 4 ga LOL.
I will start looking for a GOOD meter..thanks again
AL

 

[Meep-Meep]

By using the volt meter in series is one way to check for a drain. The 4V reading you are getting is an indication that something is drawing a very small amount of power. For example if you had the door open so the dome light was on, then disconnected the battery and hooked up the volt meter, you would read 12V but the light wouldn't come on. With everything off having only 4V indicates that whatever is draining is pretty small. Do you have an aftermarket stereo with memory? Start disconnecting every accessory you can think of until the 4V goes away.

 

[ram250098]

Great thanks very much I will get right on that....later in the week *g*
AL

 

[Scatransit]

By using the volt meter in series is one way to check for a drain. The 4V reading you are getting is an indication that something is drawing a very small amount of power. For example if you had the door open so the dome light was on, then disconnected the battery and hooked up the volt meter, you would read 12V but the light wouldn't come on. With everything off having only 4V indicates that whatever is draining is pretty small. Do you have an aftermarket stereo with memory? Start disconnecting every accessory you can think of until the 4V goes away.

I agree. It may be easier to start by pulling each fuse one at a time. If there is still a drain, then start disconnecting things. Don't forget the battery wire on the back of the alternator... good luck!