1980 f-150 just came back from the shop and its dead again! Thought my guy had it fixed. Here are my voltmeter readings.

Idle w. no accessories running: 13.4 - 13.7 (good)

Lights only: 12.50 (so-so)

Hi-beams only: 12.07 (bad)

Heater blower only: 12.40 (so-so)

Radio only: same as base reading at idle

All accessories: 11.5-11.7 (bad)

**After all tests, i turned all accessories off and it jumped to like 14.5V!!

I jumped it last night just to get home and i lost radio and lights dimmed to almost unseeable levels in a frikkin snow storm. Turned it off and voltmeter showed steady at 11 V. 14 hours later, this morning, tested at 11V still, but would not turn over....click click click. Charged it up for 1/2 hour and it started.

Notes: wiggled connection on alternator and there was no variation in volt levels. ALSO....The belt is on the pulley farthest away from the alternator on a 2 dual pulley alternator. Should it be on the closest pulley? Also, after I turned the truck off, it seemed to drop pretty quickly, about .01V every 1-2 seconds at the battery. Well below 12V now.

What to do...I am exasperated. I have spent hours posting and trying fixes and even sought professional help to no avail obviously.

 

my readings were from the battery. Should I try from somewhere else? Someone has suggested switching to a GM internally regulated 3 wire 61Amp alternator. Thoughts? Also, is there a way to test for what accessories may be causing shorts at the fuse block?

 

I'm to lazy to track down your other thread.


Is the alternator new? Battery tested good (not just a guess.) cold weather kills em. All your grounds, and connections good? If I were you I would check out these and then go to a 3g 130-200 amp alternator.

 

Battery, solenoid, alternator, and volt reg. Are 3 weeks old. Battery tests good at autozone. Thought I might have gotten a lemon but no.

 

Check your cables and your engine to body ground.

 

try this, take your thumb and press down on fan on alt. hard as you can, if it slips it needs to be tightened up,just a guess but worth trying

 

He is right, a loose slipping ALT belt would cause this.
Do you have dual ALT belts or a single belt?
Jim

 

WHat do you mean its dead again? Goes dead after sitting? You need to bring it up off of idle to check charging voltage.

 

I thought I'd be a nice guy and merge this thread onto an old one from not too long ago
but he's got *two* older ones and i think it'd be more confusing if I were to merge
everything together than just provide links here (so people can see the rather extensive
history):

https://www.ford-trucks.com/forums/1...he-source.html

https://www.ford-trucks.com/forums/1...l-battery.html

FWIW this guy has got a real Frankensteined mess on his hands.

Windsor: I think you should get yourself a factory wiring diagram for your truck, it might
make things lots easier for ya. Look on eBay or any of the automobile literature
places online; I've used Lloyd's Automotive Literature and have been pleased:
Welcome to Lloyd's Automobile Literature

My personal preference would be to remove ALL the PO-added stuff and return it to
factory configurations, sounds like doing that in your case would require a replacement
harness or two.

On an easier note, yes, an alternator not spinning like it should will cause problems
like this (to answer your question it doesn't matter on which pulley the belt is
attached).

 

Yea frankensteined would be an understatement. It all seems to have oem/duralast electronics, and edelbrock performance parts (intake manifold, air cleaner, carb). The guy took good care of it, but he did so by wiring everything "to make it work" and with whatever color wire he wanted, rendering a wiring diagram damn near useless.

Anyways....I have some progress. I braved a trip to autozone last night (no accessories but the lights running) because I have a friend there that knew I was having problems, so he called me to to let me know they got a brand new SOTA testing system that will pinpoint my problem. Battery, starter, and regulator test working, alternator does not. It is showing juice initially (where I got my good charging reading) but as soon as more power is demanded (with accessories running) under load, it will not produce. He guarantees me its the alternator, and my old one was under warranty, so the new alternator is free. What do I have to lose but a half hour of my sunday right? I have already changed it once so practice makes perfect! Wish me luck tomorrow! I hope this new testing system is right. If not, going to a GM 61 amp 3 wire internally regulated. Friend has one lying around that he bought, but isnt going to install.

 

No, not at all.

With a wiring diagram, you can figure out which factory wires get power and when, it
should then be pretty easy to figure out what the extra PO-added wires are for.

 

Single belt. It seems to be tight as I can get it. Its a single belt, but there was a duralast dual pulley rebuilt "motorcraft" alt. on it when I bought it. Seems tight, doesnt miss a beat hile spinning.

 

As the system has more demand, the alternator works harder. As the alternator works harder, the pulley gets harder to turn. This is when the belt is most likely to slip. If the belt is slipping, even just a little bit, charging output will be greatly reduced. If the belt hasn't been replaced yet, I would do so because it explains your symptoms.