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Ground Problems

Linus72

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Hi gang

So I'm having some electrical issues.
I had a bad battery and when I put in a new one, my lights flicker and the gauge says my battery is low.
I checked both new battery and alternator and they both check out as good, batt at 12.8 volts and alternator at 14.8 when running.
Yesterday it got worse as it ran badly and the battery light would come on and go back off then come on again etc.
I checked ground wire from batt to radiator support, from block to firewall, from main wiring harness to firewall.
I'm going to replace all those now even though they look ok.
The straps under the vehicle though are toast, as soon as I touched the cab to frame ground straps they crumbled to dust lol
Could the grounds under the truck do this?
So far I've replaced the egr dpfe sensor, EVAP thermosistor, battery, coolant temp sensor,and plugs.
It has lots of rust under it like it sat for a long time.
Any help appreciated!
Thanks!
 


franklin2

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Is this the 96? If so, I am assuming you have a alternator with an internal regulator. I would check the smaller wires to the alternator. One of them (used to be a lightgreen/red wire) runs from the light in the dash, and that brings the alternator online to charge. Make sure it has a good connection with no corrosion and it's not rubbed through anywhere.
 

Linus72

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Ok I'll check that.
It looks like it has external regulator...
There's a big wire going to alt, another group of wires going to volt reg, then a one wire connector going to alt.
Before this happened the dash gauge would show low volts with key on engine off and high volts with engine on flickering volt gauge and lights.
Now gauge shows low volts with engine on and battery light is on until I hit about 70mph then it shuts off?
 

RobbieD

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^^^ Good advice.

A bad main ground usually shows up in high amp demand conditions, like when starting the engine. An old trick to troubleshoot a bad main ground, is to use jumper cables, one end to the battery negative post (on top of the original cable), the other end to the engine block, or frame (or both- use both jumpers). If the problem goes away with the temporary jumper cable, the original ground cable is thus very suspect.

I think that your issue is more likely in the direction that @franklin2 is suggesting.
 

franklin2

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I don't know, the 70mph thing sounds like worn out brushes in the alternator. Check the wiring first though.

I looked up a 1996 Mazda B3000 schematic, and it shows a alternator with a internal regulator. They show 3 wires going to the alternator. Did Mazda use wires with 3 colors? They show a white/orange/pink going to the internal regulator from battery power, a black/orange as the output wire, and the one coming from the instrument cluster that brings it online to charge they show as a white/blue wire.
 

RonD

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Battery negative post should have a larger cable running to the engine, usually to a bolt that holds the Starter to the bell housing, but can be to the engine block
This cable is for starter motor and alternator as those are the largest AMP connections

There should be a Ground strap from the rear of the engine's head to the Firewall, this is the main ground for Cab electrics, its often left off after engine work so check that its there


Bad battery can ruin a good alternator
Bad alternator can ruin a good battery

Batteries last 5 to 7 years, easy to test them with Volt Meter
12.8volt when new
12.5v after 3 years
12.3v after 5/6 years and time to shop for battery sales
Test battery voltage AFTER engine has been off for at least 4 hours, test with key OFF

Start engine
Test battery voltage, should now be 13.5volt to 14.8volt, alternator is working
Under 13.5v alternator is not working

The larger wire on alternator is in B+ terminal
Test its voltage, key OFF, use alternators metal case as the Ground for volt meter
Should be Battery voltage, i.e. 12.3 to 12.8v whatever battery showed when you tested it

Unplug 3 wire connector on alternator, don't need to test the short jumper wire
Test the other 2 wires, key OFF
One should show battery voltage, if not blown fuse
Now turn key ON
Retest the 2 wires, one should now show battery volts that didn't have volts before, thats the one from the cab and the battery light on the dash
 
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Linus72

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This is becoming crazy
Alt is now showing 12.3 volts while running and batt is down to 12.3
Truck is running terrible too.
So far I have replaced EVAP solenoid and thermosistor, dpfe sensor for egr, repaired egr tube, new battery, replaced one ground strap from driver's side cab to frame, and cleaned up the grounds from batt to radiator support, from wire harness to firewall near ecm, and the strap from engine block to firewall and from neg batt to engine block seem good.
Still flickering lights and batt light stays on in dash.
Could a failing alt make the engine miss and run badly?
 

Linus72

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Note again this all started when I changed batteries.
A charger said my battery was saturated and could not take a charge.
At that time the dash gauge said good voltage whether started or not.
After changing the battery I got flickering lights, flickering dash gauge when running and when not running but key on the dash gauge said low voltage.
I did move the top rad hose off the alt wires as for some reason it sits right on them where they plug into alt.
?
I will probably get a alt tomorrow anyway lol
 

RonD

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Just test the alternator wires with a volt meter, engine OFF
Do not test alternator with engine running, ever
You can test battery voltage with engine running

Could just be a blown fuse, in a 1996 Ranger its fuse 17 in engine bay fuse box, should say Generator

Turn key on, engine off
Is the Battery(charge) Light on, if so its fuse is OK
If not then you have a blown fuse in cab fuse box, 15amp, fuse 15 in a 1996 Ranger


I think you may be under a mistaken impression on how the charging system works on vehicles
Battery is there for only one reason, to start the engine
After start up the alternator powers the WHOLE Vehicle, battery is not used

A vehicle battery's maximum voltage is at most 13.0volts, brand new
Alternators MINIMUM voltage is 13.5volts

So when alternator is working and engine is running, the 13.5v to 14.8v is powering all vehicle systems and voltage is flowing TO the battery because its a lower voltage, that's what charges the battery and keeps it charged

Right now your battery is running ALL vehicle systems because you only have 12volts with engine running
Alternator is OFF, could be a blown fuse of bad alternator
And engine runs poorly because spark and fuel are working will LESS VOLTAGE
Like a low battery in a flash light, dim light

If your old battery barely started engine or didn't start engine then it may have damaged alternator
Or alternator was already failing and damaged battery
So you replaced the battery but still had the bad alternator

Charging systems are very easy to test, 3 wires, thats all there is to it

Batteries are easy to test, 12.3v to 12.8v
 

Linus72

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Ok thanks.
I'm leaving for work soon it's about 18miles and the new alt is waiting for me
I work at O'Reilly's Auto as a delivery specialist so if I make it I'm gonna change the alt at lunch
If I don't make it I'm gonna make my manager deliver the alt to me and roadside fix
Great thing about O'Reilly's is I get a 50-70 percent discount so I've been throwing parts at this truck for a couple months
 

Linus72

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Ok so I got the new alt installed during my lunch hour.
Battery light went out, however the dash gauge with key on engine off still says battery is low and with engine on the gauge goes to a little above middle and still shakes a bit.
Also, the lights all still flicker.
I may do a warranty out on the battery and get another one as everything changed when I added this battery.
Also yesterday the truck is running badly with significant missing and sputtering including bad smell from exhaust.
I'm about to stopper up the EVAP vac hose and then interrupt the egr just to make sure neither are involved.
I got the new egr dpfe sensor yesterday and after installing it and hoses it runs even worse lol.
Will go through the egr system today and check everything.
I have so much to fix on this truck lol as I have a broken shock mount and broken leaf spring on rear driver's side and a broken lower shock mount on passenger front that I macgyvered.
The taillights don't work and I have to cut the tire carrier off to get at the harness.
It also has no brake fluid due to a rusted out rear brake line.
It's a daily driver though and don't need brakes anyway it's a stick. Pics are my quick fix on the front shock, I simply drilled the arm and used a u bolt to hold the shock on the broken stud.
 

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Linus72

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I started it this morning and running terrible so I plugged the EVAP vac hose and egr vac hose
It's still missing when cold but performance has definitely improved greatly and burning cleaner.
I'm gonna go over the whole egr system today and the EVAP system.
 

RonD

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Need to test voltage with a volt meter, and post them

Engine running voltage AT THE BATTERY terminals should be between 13.5v and 14.8volt
 

Linus72

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I have 12.88 at batt engine off and then when running 14.80 at batt.
Back to the original reason for the post as I read bad grounds can cause flickering lights or worse.
So far the only bad grounds I found are under the cab and in the back where someone used a shredder on the rear harness, likely a trailer situation lol.
I originally found a mouse nest in the air cleaner but haven't yet seen evidence of chewed wires but who knows.
 

RonD

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Cab electrical ground comes from the back of the head to the firewall, drivers side head on a V6 engine

Under cab ground is for frame ground, wouldn't cause flicking lights in Cab unless main ground on firewall was bad
Could cause flickering tail lights

Head lights are grounded to battery negative via smaller negative wire that runs to rad support bolt near battery
Should be another wire on that bolt that grounds the metal inner fender
If negative battery cable was replaced and it only has the one larger cable to engine then you will need to add your own ground wires for rad support and inner fender

The bed also has a ground strap, this was to drain any static charge as a safety precaution will filling up


Grounds are pretty straight forward
Main ground is larger cable to starter motor hold down bolt or engine block, for starter motor and alternator
Cab ground is engine to firewall, main ground for all electrics in cab, including fuel pump
Frame ground is cab to frame, used for tail lights
Rad support ground, used for head lights and horn
Inner fender ground used for relays

You can ground the frame in the engine bay

All parts are Painted before assembly, so ground does not pass easily from one metal part to another, rubber washers/pads are also common

If adding a ground clean the metal surface, install the ground wire THEN paint over it to seal it from rusting


EDIT
After driving for a bit when you get home do not shut off the engine
Open the hood and re-test battery voltage, should be under 14volts
One failure mode for alternator is voltage regulator stuck on full output, 14.8volts, this will "cook" a 12volt battery over time and shorten its life
The point of a Voltage Regulator is to prevent that from happening
 
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