Voltage drop

[Ordak]

I have 1996 Ranger with 2.3L engine and the volt gauge is steady when first started up and when running. If the truck goes back down to an idle after running the voltage gauge surges up and down or drops completely. I changed my alternator and it seems to be doing the same thing. I looked on these forums and i found that my tps could be bad but i can adjust it but i do not know how to adjust it. I am running an amp and subwoofer but even with the sub OFF it still does it. I then turned off the radio, lights, and blower and it still dropped. I have to solutions either the TPS is bad or the an idle sensor is bad

 

[RonD]

The TPS(throttle position sensor) or IAC(idle air control) sensor are for the actual RPM of the engine, is the engine idle below 600rpm?

An alternator puts out less voltage at idle that is normal, but the dash board meter shouldn't go up and down like that.
I would first get a volt meter(dash gauge could be the problem).
With key off check battery voltage, should be about an hour or so after shutting off engine
12.7v is a fairly new battery
12.4v is a battery at 50%, so should be replaced.

Start engine with lights, fans and stereo off, battery voltage should go up to 13.6v to 14.6v.
Raise RPM to about 2,000rpm, voltage should increase a little, but never over 15v

Let it idle again and start turning on things, lights, check voltage, should drop then come back up, that's the voltage regulator working, it detects a draw by the drop in voltage and adds more.

With everything on, the battery voltage should be at 13.5v at the lowest.
If it's lower then battery is bad or alternator is too small for your electrical needs.


Now check if the volt meter does the same as your in dash meter, jumps up and down when you change RPM.

Here is a wiring diagram for your charging system
http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_2.JPG

The dash gauge gets power from the key then powers the alternators voltage sensing circuit.
Make sure all the alternator wires are clean and tight, sometimes the connector wires get frayed and are only holding on by a thread, this would reduce the voltage the alt can produce

 

[Ordak]

i dont know if this helps but sometimes my truck idles high and some times my truck idles low. I do not have a tach so i cannot tell you my RPMs

 

[PirateB]

I have the same problem with idle and volt meter. The 1 grey wire connector on your alternator is probably loose causing the gauge to bounce....this is the cause on mine anyway. Have you tried cleaning your iacv to help with the idle speed?

Sent from my DROID RAZR HD

 

[Haywire6000]

How is the gauge while driving down the road? If it's still low than it's not an idle problem, or at least that's not the only issue. Have you checked the basics, belt and tensioner? Also what are you drawing with your sound system? You may have damaged the alternator or the regulator.

 

[Surrey]

Also what are you drawing with your sound system? You may have damaged the alternator or the regulator.

This is true. I've seen many cars get very odd electrical problems after putting in a big sub and amp.

Is there anything wrong with your battery other than the gauge inside the truck? It hasn't died or not charged or anything??

 

[Ordak]

This is true. I've seen many cars get very odd electrical problems after putting in a big sub and amp.

Is there anything wrong with your battery other than the gauge inside the truck? It hasn't died or not charged or anything??

It has not died or lost charge. The battery is fine i just tested it yesterday. I have a 400 watt amplifier. I used a volt meter and it reads exactly as the one on the dash. I looked at a little wire on alternator (that goes off main connector and has a little grey connector that is located under main black connector) and it seemed loose. I looked on autozone and i cannot find the connector. I did swap a KNOWN GOOD alternator and it does the same thing. So my guess is the grey connector is bad only thing is i cannot find a replacement

 

[RonD]

Look here:
http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_2.JPG

The grey(lg/r=light grey/red stripe) wire goes to the voltage meter, actually it comes from the voltage meter.
This wire turns on the alternator when the key is turned on, so very important that it has a good connection at the "I" terminal on the alternator.