Good day, F150 Forum,
I just joined, and am a novice, so please be gentle.
I will try to explain my mess on a 1992 5.0 V8:
My first signs/symptoms: I could start the truck right away, but volts read around 8. As it was idling (maybe two minutes elapsed) with all 'possible loads' (radio, blower, lights) off the volts gradually decreased until the truck died. From what I read, the fix was to check the ground wire to the starter. I replaced the wire only to have the exact issue. I then replaced the alternator and starter with no improvement. I then read that the battery might have a bad cell, so the battery was replaced. Now, the volts stay at around 8, but the truck does not die. I have not attempted to drive the truck, as I am afraid it might die. I have read online that there might be a bare wire touching and that could be sapping volts. I am at my wit's end.
I am taking the voltage reading from the dashboard voltmeter, as I am not very familiar with how to operate a voltmeter (although I do own a cheapie voltmeter).
I have noticed that if I turn the blower to high, turn on the radio, or create some other minor voltage draw the voltmeter does decrease a bit, leading me to believe the voltmeter is good.
Any advice I could get would be very appreciated, as I am not knowledgeable enough to know what other steps to take.
Thank you so much.

 

The voltmeter should be reading 14 volts with the engine running.

 

Read the voltage right at the battery. Set the voltmeter to 20 VDC and touch the black wire to the negative post and the red to positive. Should get about 11 to 12.5 with the truck off.
Start the truck - you should get 14 to 14.5 if the alternator is charging properly.

 

Thank you so much for the respomses.
The volts read 12.99 with the truck off, 13.85 with truck on. The entire time the truck was running the dashboard voltmeter read around 10. I turned up the blower motor whicch caused the dashboard voltmeter needle to dip a bit. Like a moron I neglected to disconnect the battery cable and ended up shorting out a newly-replaced starter motor. I have a new one in the box waiting to be installed this weekend.

 

Okay, the new starter motor is installed. When the truck is off the manual voltmeter read 12.93. With the truck running with no additional load the voltmeter read 12.19 eventually climbing to 12.26. With the headlights and radio on and the blower motor on high the manual voltmeter read 12.21. After idling a while I turned off the radio, headlights, and blower motor and the manual voltmeter read 12.42. I figured "a job well-done".
My wife then backed up the truck and was going to take it for a 'welcome back' drive, but she was scared off because the battery warning light came on. Would the battery warning light come on simply due to the fact it is reading the dashboard voltmeter which seems to be stuck on 10 volts while the truck is on?
Any advice you provide will be greatly appreciated.

 

With it running, regardless of load, the manual voltmeter should be around 14 volts. The battery light came on because the alternator is not charging for some reason.

 

The alternator was replaced about a month agio and the truck has not been driven since. Do you have any ideas on why the alternator isn't charging properly?

 

It's either defective or you have a wiring issue.

 

Some parts stores offer bench testing for alternators, taking it off and having it tested will tell you if it's your issue. Calling around you should be able to locate one that can test it for you.

Since you aren't sure you're really getting 14 volts if having it tested reveals it isn't defective you most likely have a wiring issue as glc suggests. Get the alternator tested before you go any further, unless you see any obviously melted or bare wire.

 

Okay, alternator tested fine. I reinstalled alternator and my results are as follows:
truck is off: 12.62 volts
truck idling with radio on: 11.96 volts
truck idling with radio and headlights on and blower (vents) at highest setting: 11.81 volts. All readings taken at the battery posts.
Before alternator was installed, both electrical connector plugs seemed okay for loose wires and plugs were thoroughly cleaned with electrical cleaner. Also, wire from + battery post to starter motor replaced using 10 guage wire, new wire rinstakled from + post to alternator (not sure of guage, but rather thick and equivalent to original).
Does anyone have suggestions for any wires/electrical connectors prone to breakage and/or corrosion? Could this be a relay somewhere? I am really tossing my hands up in the air at this point.

 

So when they hooked it up to the tester it charged, but in your truck it doesn't...
A couple things here; why was it replaced in the first place ?
You're doing a kind of hunt and peck thing as far as replacing parts to try and fix things but a new alternator starter and battery is not a bad thing to have on your truck anyway so it's not a waste of money. (although I'm confused about how you burn up a starter by leaving power on, but hopefully you didn't have to pay for the replacement ?)
2 things about the alternator; #1 you can spin it all day and it won't produce electricity unless it has some to it in the first place (called tickling it). This small charge would come from your electric circuit - I don't know which wire, you'll have to look into that maybe.
The other thing (#2) is that the boosted up power exits the alternator through the bigger wire that heads over to feed the battery. I think that by 92 that wire goes to the fender mount relay (solenoid) and is on the same post as the thicker wire that goes to the battery. Check how you've wired it and also check with your meter to see what the voltage is right at the connection on the back of the alternator. Black to ground, red to the big connection on the back of the alt.

 

Thank you for the response.
The alternator was replaced because many people said my issue sounded like a voltage regulator (built onto the alternator). When that was replaced with no improvement, people then told me it might be a bad battery cell. That is why the battery was replaced.
As for the thick wire to which you refer, there is one with the same diameter as the positive and negative wires coming from the battery. This wire is between a screw mount on tge alternator and goes directly to the positive battery post. There is a 10-guage wire oing from the positive battery post to the starter motor.
If my truck has a fendr mount relay where would I locate it?

 

The fender mount relay (what everybody calls the "solenoid") is on the fender right behind the battery. Being it's a 92 what you should see is 2 thick red wires coming off the battery pos+ ; 1 of them goes straight to the starter, the other goes to the relay on the fender (the solenoid). Usually that wire is a molded cable with that thick red wire going to one side of the solenoid - that's the side that the alternator feed goes to; also the power wires for the whole truck electrical are hooked up there. That post works as a junction block for all the power in the truck, basically.
The other side has a single thin red wire going to the starter - it goes to another solenoid mounted directly on top of the starter.
That's the newer system - it avoided putting full starter amperage through the fender mount relay (solenoid) so they wouldn't burn out so easily.

The earlier system had a power wire going to one side of the solenoid on the fender and another (also very heavy gauge) going from the other side down to the starter. This system did not use a 2nd solenoid on the starter.
Clear as mud ?
Anyway back to your charging problem - the heavier wire (usually a bolt on rather than a plug) that carries power from your alternator over to the battery (however it gets it there) should be carrying 14.5 volts when the truck is running, to keep the battery topped up.
If you're not getting 14.5 at the battery end, check it at the alternator end. If you're getting proper voltage at the alternator end, the problem's in the wire or it's connections.
If you're not getting proper voltage at the alternator end then the problem is in the alternator or the wiring to it.
I haven't (and don't have the time to) looked up a schematic of your truck but I would think that there is at least 1 wire that brings a "tickle" current - probably fed from the ignition switch - and possibly or probably a ground. There also should be 2 wires that operate the dash gauge. Anything else I'm not sure.

One other thing worth mentioning since I don't know anything about your truck is that I have heard of people having problems with their alternator if the light in their dash has been changed to an led bulb - it doesn't have the proper resistance for the alt. circuit.

 

I do not recall my truck's having a fender mount. I know I have a 10 guage wire going fromthe positive battery post to the starting motor. I do have the heavy guage wire going from a blt mount on the alternator to the positive battery post. I do have a cluster of wires going to annencased hub which appears to be bolted to the passenger side of the engine well (above the passenger side fromt wheel well). I will attemp to photograph these areas so you have an idea. I hope to post them tomorrow afternoon.

 

My solenoid is mounted to the starting motor. I do not recall anything's being fender mounted.