So after doing some brake work to the truck yesterday when I went for a test drive the truck started right up without hesitation. I drove around for about 5 minutes on the test drive. Then about 20 minutes later I went to run some errands but got a clicking noise that is typical of a dead battery and it would not turn over. I used a multimeter and the battery was showing just over 12 volts. I put the jump box on it and it started up. I checked the meter again to see if it was charging and the voltage was jumping from 6-15 volts. I then remembered that when I was test driving just prior that the turn indicator relay was making a weird noise when in use and the radio display was flickering.

So it turns out that the battery is 7 years old!! Not too shabby. I am assuming that is probably the issue. So this morning when leaving for work I thought that I would put a battery charger on the battery to charge during the day but when I went to start charging the charger showed a fault. I am assuming that the battery is toast. I plan on picking one up on the way home.

I also thought that I might check the voltage regulator as well. I have found a replacement voltage regulator at my parts store but I am not sure where it is located inside the truck. From some of the pictures I have under my hood the only thing mounted on the passenger side engine compartment wall is the starter and horn relays. Is there another location that I should be looking?

Also, the alternator appears to be original.

TIA

Ryan

 

It's under the horn on the passenger side. Or behind the second battery sometimes.

 

And the best deal I got an a reman alternator was actually a GM approved rebuilt ACDelco of a motorcraft part. It was about 70 USD. On amzxn

 

X2...if it is not on the inner fender near the starter solenoid, it's usually on the radiator support near the horn itself. If you trace the wires coming off the back of the alternator, one wire will go to the battery side of solenoid, and the rest will route to the voltage regulator. With the voltage bouncing between 6-15 volts I suspect the regulator, but I would take the alternator off and test it at the parts store when you're there to grab the new regulator.

 

My '77 has the oem alternator, but a mid '80s like electronic regulator on the passenger side of the radiator support, on engine side. Volt meter is rock steady at just over 14 volts when running, was a direct replacement for the whacky mechanical regulator.

Standard numbers, VR-166 is the electronic version, good for 1975 up through 1990, VR-613 is the older mechanical type. My VR-166 has been great since the 1980s which was when the OEM mechanical one crapped out.

 

Thanks everyone. I stopped on the way home and grabbed a new battery and also a new voltage regulator just in case.

Once home I found the VR on the radiator support below the horn.

I replaced the battery and she started right up. I tested the voltage it was holding steady at 14.7 volts at high idle and stayed above 14 volts at low idle so I guess it was just a bad battery. I definitely got some mileage out of that 7 year old battery!!

Especially for parts that are very accessible, I try to follow my late Granddaddy's philosophy of "If it's not broken, don't fix it!" When I take the old battery back to the store for the core refund I will return the new VR.

 

Working at Advance Auto, testing batteries, etc..... it did surprise me when I found a few new batteries with bad internal connections from cells or posts. They'd sometimes test OK under low amp loads, but as soon as more than a few amps, go dead.

7 years ain't bad, but regular use of a little "battery maintainer" that only puts out maybe 1.5 amps, will greatly extend that. What ages a battery is discharges and charges, even if little, over the life. A maintainer keeps it full, it doesn't let it need a charge. It floats and keeps it full.

Not just a little charger.

 

Yeah I have done that with my lawn tractor and boat batteries for years. The only thing I have found is once they do get older it only takes one time of forgetting to plug them in and they go kaput!

On my F-150 I secured the tender connected to the battery under the hood and ran the power cord just behind the grill so I can just plug it in with an extension cord without having to pop the hood each time. I will probably do the same for the F100. I am just waiting on another sale at HF!