Coincidence or did I cause the alternator to fail?

[joecool85]

I replaced the bulbs in my dash last weekend. Since then I have driven my truck 3 different days and 82 miles. My alternator died on me yesterday morning. Not charging at all (truck running was @ 11.6v when I realized what was going on). So I turned around and then took the car to work. Last night I put in the new alternator after charging my battery and everything seems alright. But it did get me to thinking, is this just coincidence or did I cause the alternator to fail when I was in the dash replacing the bulbs? I didn't do anything else while in there and the truck works fine, all lights are good, no smoking/shorts/hot spots in the wires. Only thing is I didn't disconnect the battery while working on it. I figured it'd be fine since you have to disconnect the whole gauge cluster before doing any bulbs anyway.

Of note, the alternator in question has been on my truck for 3 years and came from a junkyard Ford Explorer with 100k+ miles on it. I've put 35k miles on it or so. I replaced it with a Remanufactured USA Industries 7750 95amp unit from Motor Supply for $154, didn't have time to mess around with another junkyard one.

So what do you guys think?

**edit**
The battery is only 2 years old and is a stock Motorcraft replacement and in great shape (hopefully still is after this now that I've charged it).

 

[PanamaExpat]

Probably just time for the brushes in the old one to say goodbye.

 

[kimcrwbr1]

Allways do a complete diagnostic on the charging system. Start with the noload/load tests. One bad component can cause the other two to go south rather quick. Alternator, voltage regulator and battery. Check for shorts if the headlights flare when you goose it you need to find out why. In the tech library is a section for proper diagnostic read it through a couple times grab your multimeter and do the noload and load tests and go from there.

 

[snake]

It was a kwinkadink. No way swapping bulbs should have taken out an alternator unless you put aircraft landing lights on it and overloaded it horrifically.

 

[joecool85]

That's what I thought guys. The battery is good. It was at 12.0v after setting but before getting charged and it still turned the truck over great and it was 38F outside (not cold, but not warm either). Between that and it only being 2 years old I'm not worried about it. It appears to have taken a charge just fine as well.

The new alternator is putting out between 14.1v and 14.7v depending on load etc. It did dip down to 13.7v for less than a second but the engine had stumbled and it was just after reconnecting everything - I think the computer was "relearning" everything. Shortly after that it jumped to 15.1v but again, for less than a second and then it was back in range. The whole drive in this morning (25 miles at speeds between 25mph and 55mph) I monitored the voltage via a digital readout cigarette lighter plug voltmeter and it still stayed between 14.1v and 14.7v.

 

[kimcrwbr1]

The noload test is measure battery voltage on a fully charged battery say 12.7 volts.
Start it and let it stabilize and at 1500 rpms you want no more than 2.5 volts over battery voltage or 15.2 volts. The load test is turn everything on lights on high and heater/A/C on high at 2000 rpms you want no less than .5 volts above battery voltage or 13.2 volts. If it fails eithrer test you need to troubleshoot why.

 

[joecool85]

The noload test is measure battery voltage on a fully charged battery say 12.7 volts.
Start it and let it stabilize and at 1500 rpms you want no more than 2.5 volts over battery voltage or 15.2 volts. The load test is turn everything on lights on high and heater/A/C on high at 2000 rpms you want no less than .5 volts above battery voltage or 13.2 volts. If it fails eithrer test you need to troubleshoot why.

Great! I even pass the load portion at idle including fan (medium), lights on w/fog lights, radio on and pumping up my front tire using a compressor that draws 14 amps! I'd say I'm good to go.

I think my old j/y alternator finally just gave up the ghost. Weird timing though.

On a different note though, it sure is nice to finally be able to see all the gauges on my dash at night!

 

[wildbill23c]

Like other's have said, its probably just coincidence. As for your battery, its hard to tell. The battery in my B2 was dead when I went to pick it up as the previous owner's idiot of a son couldn't even hook up the alternator correctly so they drained the battery in it completely then just left it set for a month. I jump started it to get it on the trailer, got home and hooked the alternator up correctly, left the battery on a trickle charge overnight and its been fine since November.

 

[joecool85]

The noload test is measure battery voltage on a fully charged battery say 12.7 volts.
Start it and let it stabilize and at 1500 rpms you want no more than 2.5 volts over battery voltage or 15.2 volts. The load test is turn everything on lights on high and heater/A/C on high at 2000 rpms you want no less than .5 volts above battery voltage or 13.2 volts. If it fails eithrer test you need to troubleshoot why.

Just went out and did this test real quick.

Battery at 12.7v unloaded/truck off.

No load at 1,500rpm was 14.5v (only 1.8v above battery voltage).

Loaded w/everything on (lights, a/c on high, radio) at 2,000rpm was 14.2v (1.5v above battery voltage).

I'd say I'm good, thanks for the test though, I didn't know the specifics just that it should be something between 13.5 and 14.5v. Good to know an actual test with real numbers. It's even better to know that the truck passed with flying colors now that I have a new alternator in there.

 

[wildbill23c]

Sounds pretty good to me. The stock alternators don't put out that much power anyhow. I know mine is barely above 13 volts at idle which seems to be working just fine, haven't had a dead battery since I got it home in November.

 

[MrE_Powers]

Weather changing is hard on light bulbs, alt., and batteries why you will see more burned out lights after fronts move through the area
And why both may seem to go out at the same time
Sent from my SX-SP715A using Tapatalk 2

 

[Andy D]

Joe Cool I notice you have a Shiftster. How do you like it? The Rat came to me without the shift motor. I have a tethered vise Grip clamped on the shaft and the modes highlighted in white. It takes a little fiddling to get it into 4 high. No big deal, it isnt a daily driver. Right now it is in 4 high with the hubs unlocked.

 

[joecool85]

Joe Cool I notice you have a Shiftster. How do you like it? The Rat came to me without the shift motor. I have a tethered vise Grip clamped on the shaft and the modes highlighted in white. It takes a little fiddling to get it into 4 high. No big deal, it isnt a daily driver. Right now it is in 4 high with the hubs unlocked.

Love it, one of the best mods I've done. That said, I highly recommend doing an access panel like I did. Who wants to crawl under their truck to get it into 4wd when you're in 2ft of mud...or it's -5F outside and snowing?