Chassis Grounding Problem !!

[excetara2]

I've had problems with power to my amp. I'm getting around 1.5 ohms resistance from the ground point to the negative battery terminal. I don't know what the problem is. Any suggestions?

[Perry Babin]

Is the battery in the front of the vehicle and the ground point in the rear of the vehicle?

If so, what did you use to extend the meter leads?

[theAnonymous1]

Originally posted by Perry Babin
If so, what did you use to extend the meter leads?

Exactly, you need to subtract the resistance of the test leads, including any extensions you may have added.

[excetara2]

It's a truck so just the test leads. What is the best way to test the resistance of the test leads?

[Perry Babin]

Touch them together.

Subtract what the meter reads with the leads touching from any resistance readings.

It's unlikely that you have 1.5 ohms (or any significant resistance) from the body of the vehicle to the battery negative. With that much resistance, the truck wouldn't start and the lights would be really dim.

Why do you think there's a problem with the ground?

[excetara2]

At one point, it read 40 ohms but I fixed that problem. I just wanted to make sure it was correct.

[Perry Babin]

For all but the worst ground problems. using resistance is not useful. The current an amp can draw can cause a significant voltage drop across a resistance that's lower than you can easily measure with a standard multimeter.

It's better if you measure the voltage from a known good ground (bare meta near the ground point of the amplifier) to the ground terminal of the amp. Measure the voltage at high power. The voltage between the known good ground and the ground terminal of the amp should be absolutely minimal.

You can do the same thing at other points (battery to body, engine block to firewall...).