18v was showing on gauuges last night now truck will not start,i know thier prob is a short have no idea with the electrical system of my 85 ford ranger 2.8l. please help!....Let me explain some more things that it was doing prior to the voltage spike, after i noticed the high voltage i didnt have far till i was home so i rode it out..Maybe 5 or 6 miles that i noticed it was was ,due to the lights were alot brighter (obviously) when i let of gas lights would dim..ect ...Anyways after i gotten home it was late. The next morning i went to diagnose the problem.First thing i noticed was the battery was dead,clearly because of some kind of short. Here is were it was getting out of my knowledge, when i went to jump the dead battery i noticed more sparks than usual when i hooked up the cables shortly after the positive lead was smoking so i removed the cable tried several more times with same results, The odd thing was that my gauge would sometimes show the juice flowing and sometimes it didnt. When it did i managed to get it running once with it running about 16 vots turned it of then on 5 or 6 times back to back with no cables ..everything seemed fine. I left it alone for maybe an hr went to go leave and no juice same issue. Then i was further diagnosing the problem and noticed id get that random 12 volts showing on my gauge when id had the cables on (without them smoking ) i tried to crank her over,(i have standard btw) when id go to push clutch in and start er up ,she would show no voltage after i attempted to start......not much of an electrician so today im trying to see if i can find a short ..had not hooked anything new up to the electrical system besides a radio a few months ago and i highly dout that with make my terminals smoke when jumping it over ....guys lmk if you have had this happen or any advice at all im open to comments ,suggetions, whatever you may have for me. I believe my battery is now shot cause the high volts that was ran trough my system (later today i will take the alt and battery to some shop to hopefully rule out one thing at a time...

 

Welcome to the forum


The Alternator is the only thing that can make vehicle system show above 13volts, battery voltage is between 12.3 and 12.9 volts.

The Voltage regulator, internal or external, is what controls the alternator's output voltage.

Alternator itself has 2 parts:
The Rotor, the part that the engine spins
The Fields, 3 separate coils of wire in the case of the alternator, each Field has 2 diodes.

The voltage regulator(3rd part) sends 6 to 8volts to the rotor, as the engine spins the rotor that 6 to 8 volts creates an AC voltage in the 3 Fields, the AC Voltage is converted to DC voltage by the diodes.
The 6 to 8 volts becomes 13 to 15 volts going out to the battery/vehicle.
So the spinning of the rotor creates extra the extra voltage to run the vehicle and to keep battery charged, the battery is only there to start engine, it is not used after engine starts and alternator is producing voltage.

If voltage regulator breaks it can send more than 8volts to rotor, so you can end up with 16-20volts going out to vehicle/battery, this will fry the battery and can damage some other systems.
The fact the Light brightness changed with RPM means it was an alternator issue, for sure, and voltage regulator issue as well.
The faster an alternator spins the higher voltage it creates from the rotor voltage.

The voltage regulator is suppose to change voltage going to the rotor according to electrical demand and voltage being produced.
Its target output voltage is 13.5-13.8 volts, so as RPMs go up alternators output voltage will also go up, voltage regulator reduces voltage it is sending to rotor to keep output voltage in range.
If you turn on the head lights and heater fan to high, the voltage regulator will increase voltage it is sending to rotor because demand is higher.

The fact the lights got brighter and dimmer with RPM means the voltage regulator was stuck at one voltage being sent to rotor, a high voltage, it was no longer adapting to changing output voltage.



So start with voltage regulator, if external replace it, and check its wiring, if internal(inside alternator), then replace alternator and check its wiring.
You probably fried the battery.
With cable unhooked test its voltage, 12.3 to 12.8 volts is correct and it should hold that voltage with volt meter connected, if it is slowly dropping then it has an internal short, it is a bad battery, replace it, but not before getting alternator system checked.

It may have damaged other systems but you won't know until alternator and battery issues are fixed.

 

I had just replaced alt today, after a whle of driving the new alt went from 14.5 to back to 18 once again the battery seems fine with cables off (volatge stays constant) While cables are on the voltage will drop after a while resulting in dead battery ....It gets really weird when i took cables off while running to see if alt was doing its job To start off window wipers went crazy at full speed plus had an dc to ac adapter in cig lighter, it started to fry with both cables of i immediately went to put cables back the problem seemed to stop. As of the voltage it shot up to 18v with engine at idle, stays at around 14 when normal idle.

 

And the Voltage Regulator????????

Alternator is suppose to put out very high voltage if "told to".............by the voltage regulator

 

I dont believe thier is an external reg. on my truck ...will do more research!

 

Internal regulator alternators will have a 3 wire connector on the alternator, one of these wires will be a short Jumper wire, usually white, that plugs in to a single blade plug next to the 3 connector plug in

And a larger stud with nut connection on the back, the B+ connection, with larger wire that runs to Battery, via starter relay on inner fender

A bad battery "could" cause alternator to ramp up volts to try and recharge it.
You should NEVER remove a battery cable with engine running if you have an internally regulated Alternator, never.

That was an old mechanics trick to test if GENERATOR or externally regulated Alternator was outputting any voltage, so don't do that IF you do have an internal voltage regulator.

You use a Volt Meter now, to test if alternator is working

 

i did find a external regulator, has a vacum hose going to it ,the replacement doesnt have this. It willl be a few days till i can order a new one but will let you guys know when i get it!

 

That wouldn't be a Voltage regulator, no vacuum hose on those.

Electrical diagram for 1983 to 1985 Ranger charging system here: http://www.therangerstation.com/tech...83to1985_1.JPG

Follow the Orange wire from alternator back to external voltage regulator.

It can look like this: http://shop.broncograveyard.com/images/voltreg.jpg
Or be silver color

 

Well just got the "RIGHT" external regulator all seems fine so far no voltage spikes yet! Thanks guys!

 

Good work