Series 3 Alternator Question -> Impedance on positive line to battery

[ninescorpions]

Hey guys,
So my alternator is not charging (dash light comes on) and no voltage increase across battery when engine is running and/or rev'ed. I have checked the impedance from the alternator to positive battery terminal/cable. I am getting about 70 Ohms, but this should be 0 Ohms. Or at least the way I read the schematic, the alternator goes directly to the starter solenoid which has the positive battery connection on the same terminal. Before I go further into the alternator wiring to the solenoid, I wanted to jump the alternator directly to the battery where I know I will get 0 Ohms. I am pretty sure they alternator is toast, but at least I can confirm that. Any issues with doing this that I am not aware of?

If I do find the alternator is bad, then (based on the 70 Ohms I found), I will need to replace the alternator and rewire it to the solenoid and battery to kill this impedance buildup (unless I find connector corrosion I can remove).

Cheers!

[erik88lr]

As I recall impedance is an alternating current term. Resistance should be the appropriate one here, IMHO.

In any event, it seems that if you disconnect the wire from the alternator you should have no resistance between it and the positive battery terminal. You might try straight wiring it, but it sounds like your alternator is toast. I'd install one of our hosts rebuilt units.

[slowmo]

Measure the voltage between the battery terminals with the truck not running. Start your truck. Measure the voltage between the battery terminals. If the voltage is the same or a bit lower, the alternator circuit is not working. Now, if you can reach the alternator with the truck running measure the voltage on the alternator terminal itself. If this voltage is the same or a bit lower, alternator is toast. If this voltage is 13-14 volts, the alternator is working but you have a open somewhere. Find it with the truck off, using the multimeter in continuity mode (beeps with circuit continuity).

[ninescorpions]

As I recall impedance is an alternating current term. Resistance should be the appropriate one here, IMHO.

In any event, it seems that if you disconnect the wire from the alternator you should have no resistance between it and the positive battery terminal. You might try straight wiring it, but it sounds like your alternator is toast. I'd install one of our hosts rebuilt units.

Roger that!

[ninescorpions]

Well I finally got this problem fixed. With a new alternator and new wiring between alternator and battery...charging is back in the house!

[Les Parker]

Thanks for the positive feedback, always is good to know when a solution is found.