Need help with voltage

[hotlavaflow]

I'll try to give as much detail as possible. I only have a couple hours per day to trouble shoot and I'm hoping someone can point me in the right direction.


PROBLEM:
Car isn't seeing 14.0+ volts while running but battery is.
New alternator (Nissan Quest) New battery (Mazda Miata)
Test at battery reads 12.6v with DVOM while off
Test at battery reads 14.2v with DVOM while running
Test at ignition reads 12.2v with DVOM while off
Test at ignition reads 13.9v with DVOM while running
SAFC-2 shows 13.3v at start up drops to 12.8v while driving

EVERYTHING FROM HERE IS BASED ON SAFC-2 READING

HIDS on 12.3v-12.6v then back to 12.8v
Electric fan #3 on 12.6v then back to 12.8v
When volts hit 12.6 or lower car wants to stall, I have to gas it

I can't drive very far because the volts will continue to drop over time it's been down as far as 12.0v.

ALSO:
Relay under the dash near the fuse box to the left buzzes occasionally and the brake light comes on when it buzzes. It will buzz while idling (parked or red light, stop sign etc.) if I turn the wheel back and forth.

The battery light on the dash glows faintly

Car starts everytime no problems.



I need some assistance.

[GSXRJJordan]

Good news: Alternator and battery seem fine.

Bad news: You need to spend some time troubleshooting your grounding issue. My guess is you have an engine-to-chassis ground problem, but also take a look at your battery-to-chassis ground (the OEM ground strap goes from the battery to the engine to the chassis). Make sure your ground wires and terminals are in good shape (not brittle, frayed, etc) and that the metal they're connecting to is free of paint/debris/etc - you want some nice metal to metal action.

The fact that so many things have low voltage leads me to believe that the interior grounds are not the issue, however if you troubleshoot the major grounds and still have an issue it might be worth checking the relay box grounds. My guess is this will be a case of something not connected at all.

[hotlavaflow]

Damn engine to chassis that makes sense. I had a feeling it was something like that. I'll report back later tomorrow.

Thanks for the quick response. I might go outside with the flashlight now and make that correction.

[Twin]

Have you considered perfoming a leak down test? Seems like something is draining your battery while you run.

[GSXRJJordan]

Originally Posted by Twin

Have you considered perfoming a leak down test? Seems like something is draining your battery while you run.

Lol low cylinder compression somehow takes more electricity? Negative.

[Nizzan4u2nv]

Originally Posted by GSXRJJordan

Lol low cylinder compression somehow takes more electricity? Negative.

Thats what I was thinking hah. I guess he means testing for parasitic drain.

[NismoTuner21]

Can someone explain the importance of grounding the engine to chassis?

[GSXRJJordan]

Originally Posted by NismoTuner21

Can someone explain the importance of grounding the engine to chassis?

Absolutely. When the car's off, the battery is the only voltage source. You need a good ground from the battery to the chassis in order for anything else to have proper voltage.

The starter grounds to the engine block, so in order to have good voltage at the starter, the engine block needs to be grounded to the chassis.

Things get more complicated once the engine is running, because the engine block itself is now the largest source of electrons, and the alternator is providing voltage for the car's electrical system (as well as recharging the battery) - and the alternator also grounds to the engine block. Overall, the amperage the alternator provides is lower than the amperage the starter uses, but it's still significant. This is why not having a good engine ground can cause cranking problems as well as low voltage problems when you're running.

It's also possible the alternator fuse can be blown, its the 80A or 100A fusible link inside the engine bay fusebox.

[Twin]

im sorry not a leak down test. its a leech test or some sort.

[hotlavaflow]

I checked the alternator fuse and it's working.

I ran new grounds from battery to engine and engine to chasis.

Still see the same thing.

Can anyone ID these plugs? They are from the harness and end near the fusebox/battery area. They aren't plugged in.

Have a long drive Saturday for Formula D need this resolved asap.

[GSXRJJordan]

A/C triple pressure switch on the left, A/C fan on the right I believe.

How'd you test the alternator fuse?

[hotlavaflow]

Put 12v on one side and saw it on the other prong with my DVOM. Hope that's right.