calling electrical guru's Voltage Questions Options

[Ferg]

The gauge in my car reads almost 2 full volts low, compared to the battery. I have tested the battery it is 12.5 with car off. With car running at idle it is 12.8 ish, and at 2k rpm and above it is at 13.8. The idiot light on the dash does stay on when first started, but goes off as soon as I blip the throttle.
So when idling my dash gauge reads 10.5ish and goes to 12ish as soon as gas is applied. While driving the dash gauge stays around 12 unless headlights are on then drops back to 10. But if I check the battery with headlights on and at 2k rpm it is still at 13.8 and there is no volt drop when headlights are turned on and off. So my question is where do I go from Here (IMG:style_emoticons/default/confused24.gif)
Car is a 2.7 conversion if it matters, and battery is yellow top altima.
Ferg.

[Drums66]

Check everything in the charging curcuit, alt,Voltage regulator, Battery, ect. I just had a run around with a bad battery myself! in a FI car a bad battery can have you looking in all the wrong Places (IMG:style_emoticons/default/blink.gif)

[ArtechnikA]

The gauge in my car reads almost 2 full volts low...

i presume you're talking about the center console gage.
it's located (electrically) in a part of the car where its information is just about useless, although it might be helpful on a comparison basis (if it used to read '10' amd now it reads '8' - go find out where your alternator belt went ...) .

clean all the grounds, freshen up the electrical contacts - that'll help it be more accurate.
but probably you should consider it to be the 914/4 equivalent of the 911 oil tank level gage - information provided for entertainment purposes only.

accurate voltmeter readings are available at the battery posts directly, or - in the case of charging system output - the starter +12V post. if you really want an accurate in-car gage (not sure why...) run some #8 AWG wiire from the battery posts top the gage.

[Brad Roberts]

Grounds. The center console has poor grounding from the factory. I like to ad a small wire from the harness ground to a bolt on the shifter base.


B

[Ferg]

Thanks for the replys. It's been that way since I bought it, without much change, but recently the idiot light has been coming on during start up which prompted me to retest everything. I have not gone "behind" the dash yet though.
Ferg.

[Brad Roberts]

What dash do you have ?? Stock dashes dont have volt meters in them (they are down in the center console).

Do you have a combo gauge or something with a volt meter in it.

Curious as to what you have.



B

[tryan]

my center console gauge reads 1.0 volt lower that what a digital meter reads at the actually battery terminals. even with all clean connections. the gauge is for 'entertainment purposes only'.

see if the points on the voltage regulator need to be cleaned. there are two circuits. one for idle and a second through a shunt resistor for higher engine speed. check the non-shunted cicuit.

[Brad Roberts]

Talk to US more about the contacts for idle. Every damn 9146 I drive turns the alt light on at idle. I would like for this to stop happening.

B

[Ferg]

I have the center council. That's where my voltage meter is. The red idiot light comes on the dash, brake light up top, gas on bottom, Voltage light at 9o'clock oil light at 3 o'clock.

[tryan]

you can adjust the mechanical regs, but getting the light to go away at idle would require more field current. ie. clean the #9 fuse routine.

on the 4's, checking the ground from the relay board to the alt would be the best start if the regulator points look okay. do the 6's have the same board? the pencil wiring diagram for the 6's on pelican sucks. i have a hard time focusing/reading that puppy.

to cure the dash light at idle woes, logic tells me that adding a ballast and a diode to the hot feed at the idiot light at the dash. (mallory makes an inline ballast wire.) this will keep the light off until it drops to 9 volts.

[Dave_Darling]

Also clean up (or replace) fuse #9 and clean the metal "fingers" that hold it. That will often cure the alternator light being on at idle.

--DD