Electrical When should I have continuity?

[James.Little]

I have been fiddling around with my car since I stuck in my new 3g alternator. I had too much amperage going through a 10AWG (the wire off of the ground battery cable to the ground wire on the driver side, near the battery tray) and caused it to melt and caused the car to shut off. I then read online that I was suppose to have a 4AWG wire coming off of the engine block to the ground on the driver side (Near the battery tray). Which I did not, until now. So now I have both, however I am afraid that something like that will occur again, so before I install the battery I want to know what I should expect.

Let me state, I bought a cheap fuse holder, the plastic that the fuse and wire connects to, fell off and caused the cable from the alternator to touch a bolt, which was attached to some metal on the car, causing it to ground out. I fixed that, but I then found out I was missing a ground cable, which my situation would not have happened, if I had that cable.

So I installed a new fuse holder (same cheap one, till a better one arrives) and taped the crap out of it. Replaced the negative side battery cable, and the attached 10AWG cable. Added a 4AWG ground cable. So now, I am checking continuity. I am a bit confused on what the outcome should be.

I attached one probe to the positive post on the alternator and one probe to the positive battery cable, clear beep!

I attached one probe to the back of the alternator and one probe to a random screw that held the fuse holder (no longer in use), it kinda beeps, but I have to constantly move the probe on the screw for it to beep. Should it do that?

I attached one probe to the positive battery cable and one to the negative battery cable, clear beep, is that right?

I attached one probe to the positive post on the alternator and one probe to the negative battery cable, it is a clear beep, is that right?

Also, I did move the yellow wire from the wiring harness to the positive post on the alternator, as a alternative wiring solution.

Thanks for the help guys (sorry for the long post)!

Also my mustang is an 89 5.0L 5-Speed.

 

[jrichker]

As long as you have the battery cable on the negative post of the battery, you will get strange readings with a resistance test.

Here's why:

With the battery cable on the negative post of the battery, there is always a small amount of current flowing through the battery cables. This is due to the keep live voltage for the radio presets, clock and computer. Granted it is not much, but it can be enough to upset the accuracy of the ohmmeter's measurements.

The reason is because the ohmmeter measures the voltage drop across whatever it is measuring. There is a small voltage coming from the ohmmeter anytime a resistance check is made. The ohmmeter measures this voltage drop across the item under test and compares it to the source voltage being supplied by the ohmmeter. The voltage drop from the component under test is added to the voltage drop across the live conductor and that throws of the true resistance calculation.

 

[James.Little]

That makes sense. Did I mention the battery is not in the car at the moment? Does that mean everything is working fine and I can install the battery and try to start the car? Thanks for the response!

 

[James.Little]

Good news, car is in good shape, electrical wise.