I have a new battery and a reman alternator, I show a full 14v at idle with all accessories including defrost, and about 14.4 - 14.5 at 1500rpm with a DMM, however, the in dash gauge never goes over 13V at 1500 RPM with no accessories, and less than 12v at idle with all accessories, accessories are lights, heater CD player and defrost. So obviously this is a problem with the grounds going to inside the car, well at least thats what im guessing. What wires should I be looking at to fix this problem.
BTW, the lights in the dash dim and the voltage drops when going to idle as well, also when applying the brakes (lights obviously) however I dont think it should be this low of a drop when I still have 14V at the battery/alternator.

 

Mine does the same thing. My alternator is putting out ~13.8 V at all times, yet my gauge in car never reads over ~12.5 V.

When I put my shifter in reverse it drops to ~11.0 V.

 

I guess no one knows what grounds I should look at? This is really irritating.

 

It may not be a grounding problem. First, take a look at this:

http://www.aaroncake.net/rx-7/grounding.htm

Secondly, look at the wire that runs from the alternator terminal to the fuse box. It's likely corroded and burned. Replace it with good thick 8 gauge wire and new terminals.

 

I have always found my stock voltage gauge to be off by about -2 volts.

 

I got some 10gauge plus cleaned up the stock one going to the battery directly, plus im always showing 14v or higher at the battery. I tried doing the ground under the trailing coil, but maybe i didnt do it well enough?

 

Have you verified the low voltage problem with another voltmeter?

If you are reading 14V at the battery, you are probably fine.

10 gauge is WAY too small. 8 gauge is the smallest you want with the alternator lead and leaving the stock one in place is useless. Electricity always follows the path of least resistance so the stock lead does nothing if you have added a 2nd. Unless the 2nd is too small of course so it's resistance is too high under large currents, in which case you have two leads that are useless.

 

Ok, I know this is an old thread, but my positive battery wire going to the terminal came loose in the terminal one day, and when this happened, by voltage was magically where it should be inside the car at 14v or so, does this mean the regulator wiring is bad? What should I do?Could I set up a relay from the ignition switch to send the battery voltage to the alternator when I turn the ignition swicth on? Or should I send the voltage from another point in the car? Perhaps the voltometer reading itself?

 

Actually, that happened to me. When I was having problems with my battery terminals, my voltmeter would shoot around from where it's normally at (~12) to ~14.

 

Well i mean its fixed now, the terminal, but it still runs 12 - 13v

 

Yeah, I fixed the terminal and it went back to showing ~12V.

 

Run A Bunch Of Grounds Get A Grounding Kit

 

I dont understand your philosophy. Thats like saying that having two resistors wired in parallel would yield the same resistance as having one resistor, when that is definitely not true. If you have two wires, reguardless of the guage, shouldn't they both deliever electricity to wherever directed? By using a precise ohm-meter, two wires in parallel would appear to have less resistance, and therefore the amount of amps it could pass would be greater.

Pertaining to the voltage meter, isn't there a chance that the amount of resistance from the length of wiring from the battery/alternator would reduce the voltage from ~14v to ~12? Though the grounding location may not be far from the unit itself, the electricity has to flow through a large length of wire carrying the positive charge(most of which is of a higher guage wire=more resistance).

I could be wrong on these points; I am using knowledge from another application since I just purchased my first car not too long ago.