troubleshooting charging system

[Keoke]

Volfandt has a good idea on the battery drain test using a light bulb, however, you must use a very small bulb (#53, dash lamp) in order to pick up low current drains. A large bulb like a 1056 or an 1156 ( 4 amp tail & signal bulbs) will not come on at low current drains. The low current flowing across does not heat the filament, conductor when in series, enough to put bulb on for one to see.
On having 13v dc at reg/rectifier and only 11 at battery.
Because of time, voltage drops that are hard to find are sometimes best left alone in a harness to die. Consider running new 12 gauge wire (for 10 A chg) from your regulator alt output to battery B+ at starter solenoid or battery post.
Of course you want to be sure that the old alt to battery wire does not split off in a "no see area" to something else ahead of battery before you do this. So, as a temporary measure you may want to put new line in parallel to old line to see if voltage drop is reduced.
One last thing, as we all know, voltage drop is proportional to current flow. So, with engine off, 11v at battery and the same 11v at the VR unit does not mean that this is a good circuit. A wire with just one continuous strand out of 20 possible, would show the same voltage at both ends if there was no current flowing in circuit.

cheers,

 

[Volfandt]

Thats a good idea to scale down the size of the lamp even tho I've had pretty good success with my old 1156 lamp tester. /forums/images/graemlins/grin.gif

Volfandt

 

[coloradotrout]

Let me toss in one more curve.. which I think I tossed before, but what the heck. When the battery is dead, and I jump, and run it for awhile, it's still dead. When it's down, the engine running seems to supply no charge at all. That's what lead me to the idea that I must have a charging system problem. It's a big mystery right now. I put all the covers back on.. will see what happens. I may take the battery in to have it checked. It's an Optima.. from Autozone, but who knows, maybe it was bad.

 

[Soundguy]

Sounds like an 'open' betwixt charge output and battery terminal...

Soundguy

 

[coloradotrout]

I know, that seems logical, but there is a connection from pos. term to starter to fuse to rect/reg. Off.. I see battery voltage at the rect/reg. Running, at the rect/reg there was about 13V, but 11V at the battery. Since I read voltage at the rect/reg when OFF, that circuit is good, or would seem to be. Now I'm suspecting the rect/reg. I read on some tractor parts site, that is a common part failure. Uuuugh, but $100 I'd like to know for sure before replacing.

 

[Soundguy]

Still.. Like "scotty' used to say.. you can't change the laws of physics'. If you have 13v at one point in a wire.. and 11v at another point.. you have a votlage drop... no if's and's or but's.. Now you gotta find out why... Some component in line.. etc.. Bad connections.. frayed broken wires.. etc. Find the source of the votlage drop.

Soundguy

 

[Keoke]

Quote:
Running, at the rect/reg there was about 13V, but 11V at the battery. Since I read voltage (11v) at the rect/reg when OFF, that circuit is good, or would seem to be.

Coloradotrout,

Seeing the same 11 volts at the battery and VR unit with no current flowing means nothing in regard to circuit quality. Current must be flowing in a circuit to measure dynamic (while working) voltage drop. Static voltage readings at both ends of circuit mean nothing when checking for circuit quality. Showing 13v at VR unit and 11v (at weak battery) means that you are taking a 2v hit in moving current from alt to battery, peroid. To confirm this, put voltmeter on low scale over 3v with pos lead on VR unit (most pos pt.) and neg lead on positive battery post and you should read around 3v. This is the voltage loss from the start to finish on this run. As Soundguy said earlier, you cannot charge a 12v battery when coming at it with 11 volts. Industry standard for charging circuits is no more then .3 of a volt drop for every 10 amps flowing in circuit. The .3 is not a good number, it is the max allowed.
Consider doing what I suggested in my last post, that is running a temporary 12 gauge jumper from VR unit to battery and then checking the voltage at both points, or better yet with the voltmeter in parallel (across) both ends of the jumper.
Also, you should check that battery, it is best to do all your testing with a known good battery.

cheers,

 

[coloradotrout]

I'll run the battery back to Autozone for a load test, then also hardwire that rect/reg to battery. I have to pull the console off to get at that rect/reg, and maybe disconnect the "cruise" control and park brake. That's the worst part.

 

[Soundguy]

Keoke is giving you good advice about measuring the voltage drop on the line, and then jumpering it and ovserving the meter. Even a set of aligator clip leads will work for the test.. may be easier to hook up as well.

Soundguy

 

[rvtech]

Be sure AZ is testing the battery correctly. A discharged battery cannot be load tested. They must confirm the battery is fully charged before they test it.. They usually use a carbon pile tester which will show any discharged battery bad. That may be what happened with your original battery.