My Son’s car was in an accident (no fault). Infinity g35 (2003). I’ve helped him rebuild. Everything has gone together square as there was very minimal damage outside of cosmetic.

Since the accident his battery light has been coming on. Initially checked the alternator and it tested good. Took the battery in and it tested bad. Replaced battery. Car was good for a couple days and battery light returned. He took the car to have the alternator checked. Tester said alternator was faulty (over charging)and was replaced with a reman. Was good for a week or so. Battery light comes on again. We jack it up and there is an arc occurring. We look into it and a mounting bracket for the alternator was not bolted on correctly (previous to accident as he’s not touched the alternator prior to accident). Looks like the power lead to alternator is touching the incorrectly mounted bracket causing the arc.

He gets the correct bolts and attaches a new OEM alternator and mounts the bracket correctly. Initially battery light comes on on first fire up. We clean the power lead (to battery), unbolt the power line to alternator post (he thinks he may have over tightened) and snug it up. No more arcing, but while running, battery light is NOT on but volt meter on the battery reads 11.8 volts (not charging). We checked every fuse we could find related to the alternator and all looked good (replaced one that looked possibly corroded).

I’m at a loss and hoping for direction on what to check next before we have to take it to a shop.

Confident on mechanical fixes but electrical issues aren’t my forte.

Any direction is appreciated.

Thanks,

CT

This message has been edited. Last edited by: ChasinTails,

Check and tighten all the grounds.

Best wishes to you.
.

Make sure the plug for the voltage regulator is fully seated.

That voltage reading is with an external VOM correct? Not just the dash gauge? If it is I would have the new alternator tested. It’s not like you never get a bad part NIB.

quote:

Originally posted by Shifferbrains:
Make sure the plug for the voltage regulator is fully seated.

Thought of this...

We unplugged this, cleaned contacts on the plug and alternator and reseated the plug making sure it “clicked” into place.

quote:

Originally posted by Krazeehorse:
That voltage reading is with an external VOM correct? Not just the dash gauge? If it is I would have the new alternator tested. It’s not like you never get a bad part NIB.

Correct. Instrument cluster has no voltage reading gauge. Used an external Voltage meter. This is the second alternator we replaced. First was reman and second is brand new OEM.

quote:

Originally posted by OKCGene:
Check and tighten all the grounds.

This is next on the list. Gonna have to try and find where they all are. Have a feeling it’s gonna be a long race...

Check the entire run of battery cables for damage. Including the cables that go to the alternator.

Use an Ohm meter to check the alternator's ground and as many others as you can find.
Connect one side to the battery negative terminal and touch the body of the alternator with the other to be sure it has a good ground.
Then do the same at any other grounded terminals you can find, especially if they were disturbed from the accident or repairs.

Is the voltage regulator an integral part of the ECM/PCM/VCM?

Might need to scan the computer.

quote:

Infinity g35 (2003

Wiring Diagram from Battery, may help you trace the problem, more at the link

The Link

Update..Still haven’t found the problem.

So, here’s what we’ve done: checked and cleaned all grounds. Replaced both battery terminals. Unplugged the regulator connector and cleaned plug and regulator contacts with contact cleaner. Visually inspected the power lead wire and contact at alternator post. Checked the accessory belt for slipping and alignment. All looks good.

Testing voltage at different times we’ve found that the alternator is charging at idle, showing 13.9-14.4 volts. When the throttle is pushed, and the rpms get to around 2500, the light starts to come on and the charge drops.

This would lead me to believe that something is drawing too many volts and the alternator can’t keep up. But the only non-stock add-ons he’s done are a new radio deck, a boost gauge and an oil pressure gauge which wouldn’t seem to have too much draw.

I can’t believe that we would have gotten two bad alternators (one reman and one oem). Is it possible the the connector to the regulator is bad and may be the issue? If so, Is there a way to test the plug before replacing it?

Thanks,

CT

While running under load (all accessories on), try voltage drop testing. Set the meter for DC volts and check between a solid metal part of the engine and the negative battery terminal, and between the alternator output terminal and the positive battery terminal. There should be no more than 0.5V, and less is better. Another quickie test you can do, but only for the ground side, is with a jumper cable. Hook the ends of the same cable (the black one for simplicity's sake) to a solid metal part of the engine and battery negative. If you hear a change in sound and the voltage increases, there is definitely a grounding issue. And was everything OK before these accessories were added?

Problem solved for now. Thanks for all the guidance. After changing battery terminals, cleaning every ground, checking for continuity and voltage in every wire imaginable, pulling fuses and relays and tearing this damn car apart multiple times, it seems we’ve solved the problem...by putting in a 3rd alternator.

Too bad you can’t expect new alternators to work out of the box. This was number 3. Buts that’s for the rant section.

Learned a lot about electronics/wiring along the way. Way more than I wanted, for sure.

Thanks again.

CT

Not just alternators. Saturday evening, brake caliper stuck. Only place open was AutoZone, not my first choice but…

Try to bleed, leaking at the hose to caliper fitting. Seems the threads were messed up and apparently the rebuilder thought good to go. So Sunday morning, rinse, repeat. Second time’s the charm they say.

Friend just replaced a front caliper on his truck, wheel bearing went out and started a mini conflagration. So new hose, etc. Installed, bled, piston stays applied. Break bleeder loose, negligible pressure remained, piston stays out. So he’s off for another caliper today.