So i was fooling around with my multimeter the other day (checking tps) and discovered that when i touch the alternator housing, an the NEG bat terminal, I get continuity. For my multimeter that means it goes beep and shows 0.0 somthing ohms. When I tested the bat to a bolt on the chassis, which I scratched through the dirt/zinc I got like 250 ohms. I get about the same reading from other spots on the frame. Things are still grounded, and (i assmume) working properly, but i'm still kinda wondering why.

Any Ideas?

 

Use the multimeter set to DC volts and place one lead on the alternator housing and the other on the negative battery post (not terminal but the post) and w/the car running it should read less than .2 volts. If higher the grounds need to be cleaned up.

 

You may have to really clean the area with a wire wheel to get a good reading.

But why not just pull out the bolts and clean up all the grounds while you are in there? Clean the terminals, replace if necessary, use new stainless bolts, run a tap through the threads, wire wheel the area down to bare metal, cover with dielectric grease and reassemble.

 

I'm going to redo the main power wires sometime in the near future. batt to starter, power and ground as well as the alt. wire. I just cant do it now.

It just seems strange that a bolt on my engine that is just as crappy and dirty as the one on the chassis read different. Oh well, story of my life.

 

You can always go to the auto parts store, look in the $5 bin + get yourself some thick speaker wire. Then add an extra ground from the battery to the chasis w that. I did it a while ago just in case.

 

ALTERNATOR CIRCUIT VOLTAGE DROP TESTS

With the engine idling, touch one test lead of your voltmeter to the battery positive (+) post, and the other test lead to the BAT (B+) terminal on the alternator. Ideally, the voltmeter should read less than 0.2 volts.

If you see a voltage reading greater than 0.2 volts, it means there is excessive resistance somewhere in the circuit causing a voltage drop in the wiring circuit. Check all the wiring connections (use electronics cleaner to clean connections), and make sure the terminal connectors on the ends of the wires are clean and tight.

A negative side ground circuit test is made by touching one voltmeter test lead to the alternator housing, and the other test lead to the negative battery post (not the terminal clamp) with the engine running and charging system loaded. If good, the voltage drop should be 0.2 volts or less. If higher, inspect and clean all ground connections as needed. Also, check for broken, loose or missing ground straps between the engine and body.If the alternator output circuit and ground circuits test good (voltage drop less than 0.2 volts) and the vehicle has a history of repeated alternator failures due to burned out diodes, check for a shorted indicator light terminal.

Checking for voltage drops in a circuit is a good way to find hidden problems that may be causing a charging problem. Voltage drop tests must be done while the engine is idling with a charging load on the system. In other words, there must be voltage flowing through the circuit for the voltage drop test to detect a problem. Voltage always follows the path of least resistance, so if the connection being tested has too much resistance some of the voltage will flow through the voltmeter and create a small voltage reading.

 

incubuseva - I was going to do a quick ground strap from the batt neg to the chassis just to add a little help, I just have had a chance to go through my wire box and fine some 8-10 gauge wire.

Satch - Great info! I'm going to try this tommorow (between rain showers)

Thanks