My instrument panel idiot lights went dead some time ago. About the same time, my battery started going dead on a regular basis. Tried a new alternator with no luck. Had alternator retested and it is okay. Battery charges on battery charger, but does not charge on the alternator. I suspect problem with idiot lights and charging are related. I want to replace the light with an ammeter, but I suspect the idiot light is a necessary part of the charging loop. Any advice is appreciated.

 

Welcome to FTE!

You didn't state what year truck this is on.

First off:

1) If alternator bench tested good and replacement didn;t provide a change....... move on to something else in charging system.
2) Wiring to Voltage Regulator
3) Voltage regulator (what I thinbk the problem is)
4) Wiring from starter relay (battery) to dash ie: Fusible links
Remove wrap from harness and look for melted wires.
If you find melted wires ,you need to replace the fusible link (s).
But beofre you hook power to it you need to find out what caused the melting.
My guess is the instrument cluster where the idiot light hooks up.

Remove the cluster to inspect the back of it.

Do all this inspection and report back the results.

This is from a 79 but will be the same a few years back.

 

Just simply check and see if the wiring at the alternator, regulator and the battery connections are at least not corroded. Then while you are looking for that problem if there are any loose connections or broken wires you should find them as well.

 

I got the same kind of problem on a 76. I replaced alt, starter, voltage regulator all wires and fusible links OK. Only thing left is the starter solonid.Sometimes the battery will get a little charge but never over 12.9 v. At 12.8 v or lower there is not enough power to start the engine.

 

I try to help people trouble-shoot the problem so they don't have to spend money unless they really have to.
That's why I don't suggest replacing parts *****-nilly..anybody can do that.
I prefer to figure out the problem first

 

First time posting and I need ya’lls help.
My 79 f150 4x4 has the same problem. I have replaced the alternator, voltage regulator and have ohmed all the wires I can find coming from or going to the alternator or voltage regulator. But the problem persists. The truck starts on the first crank and runs great as long as the lights, radio and air conditioner are not on. Turn on any of them and the battery starts to die. The batter never goes above 12.4 volts, and when the lights are turned on it goes down to about 11.9 then starts to fluctuate.
I am lost as to why it’s not charging. HELP.
Randall

 

What Dennis said.

When first looking into an electrical problem I found it's best, not to disturb anything by "looking:/" at wires etc. Find the trouble with a meter first, only then, repair.

If it's intermittant that's a whole nuther story :/ but if you've familiarized yourself with the system ahead of time and wrote down some voltage drops across certain things and the resistance of others etc then even a "cleared up" intermittant problem my show itself during a "once over" with the meter.

(rant mode on)
A plumber doesn't need a meter to figure out if he's got pressure and flow to a certain point. But he ain't working with something he can't see like water or feel like air, neither.
(rant mode off)

A couple guys here are using meters and that makes me feel all warm and fuzzy inside.

It's hard to help you from here tho, sorry. :/

And for trouble shooting an analog meter will beat a digital meter.

Normally I would qualiy a statement like that but that's been hashed over on several automotive newsgroups and when there's an analog buff willing to stick it out, that's the conclusion reached everytime.

Do we need to go over it here too?

Alvin in AZ (retired RR signalape)

 

I'm sure some will disagree with what I'm about to say, but without the proper tools and equipment, chasing an electrical problem can be like a dog chasing his tail. If you have the time and knowledge go for it. If not, a self igniting type alternator (1 wire hook-up) may be the quickest, cheapest, easiest repair. Bolt it on, run a wire to the positive side of the battery or solenoid (through an amp or volt meter if desired) and enjoy driving your truck.

 

Were these values at Idle or above 800 rpm ?

The VR doesn't "Kick-In" until the engine is running at about 800 RPM

That's when you check for the charging condition.

I normally do "Electrical Draw" tests at idle & 1000 rpm to see whether everything is working under all conditions.

Draw items are:
Headlights
Heater
Wipers

 

It was at Idle, I had no one to help.

 

You shouldn't need help.

raise the RPM but actuation the throttle under the hood

 

As soon as I received a notice stating I had a reply I thought I could have done it by myself. (Hello any one home) sometimes you just feel like a idot.
what should I see on the battery above 1000 rpms? 13 volts or higher?
Thanks
Randall

 

yes,
Most run about 14.7v to 15.2v without any draw.

add one draw item at a time until all are on writing down the values as you go.

 

See the problem is the system is never up above 12.4 I have taken it to have the alternator checked and auto zone and they had the truck up to 1000rpms and when the automated test was complete they said your system is not charging you need to check your wires. so I'm back to the wiring harness. I found a harness on here for about 400 bucks. I'm thinking I'm going to change out the motor that's in it becuase its too much motor for the truck and have the harness redone professionally when I do that.
By the way, the motor is a big bad A$$ 461, and I want to replace it with a 302 , any one willing to make a trade? or buy that big sucker. I have all the paper work on the rebuild and it has all kinds of proformance parts on it.
Thanks
Randall

 

It could be the alternator but ...Sounds like a faulty Voltage Regulator to me.

460 to 302
That truck with a 302 will burn almost as much fuel to get it rolling and maintaining as the 460 does.
You'd be better off with a performance built 400.

Not as much to swap over as some parts inter-change and used parts are plentiful.

You can sell your engine in the FTE classifieds