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I'm working on my '84 F250 and am trying to figure out why all of my electrical accessories are receiving 14.2 volts with the engine running? Is this normal (my gut tells me no...)? So I immediately think voltage regulator. I went through all the tests in the shop manual and all roads point to it, but with a new regulator, it's doing the same thing. This concerns me because with the engine running, my ignition coil is registering almost 11 volts and I know it should only be around 7 or 8, but also, my electric choke on the Edelbrock is 14V, as is the wiper motor feed. These all seem too high... Please help!
I'm working on my '84 F250 and am trying to figure out why all of my electrical accessories are receiving 14.2 volts with the engine running? Is this normal (my gut tells me no...)? So I immediately think voltage regulator. I went through all the tests in the shop manual and all roads point to it, but with a new regulator, it's doing the same thing. This concerns me because with the engine running, my ignition coil is registering almost 11 volts and I know it should only be around 7 or 8, but also, my electric choke on the Edelbrock is 14V, as is the wiper motor feed. These all seem too high... Please help!
A few quick thoughts:
1) Was the battery fully charged before taking that reading? If the battery is low, the charging voltage will run higher to compensate. Don't launch the parts catapult yet. 14.2 is high, but not beyond the normal range if the battery voltage started out low. Does the voltage settle down after a few minutes, or does it consistently remain high?
2) Try running a dedicated ground between the alternator case, the base of the regulator, and the battery's (-) terminal. The ground at the regulator is iffy at best. A bad ground there can cause all sorts of electrical !mayhem. Here's a long thread you may find of interest. Grounding the regulator base was the fix:
13.8 to 14.3 is normal, and exactly what you want to see. 12 volt batteries should really be called 13 volt batteries. At least they are closer to 13 when at 100% charge and a serviceable battery will always read over 13 volts before the "surface charge" is removed.
An automotive battery takes about two (2) volts above and beyond the normal at rest voltage to reach 100% charge. At 70F. When it gets cold a correction factor is applied, even higher voltages are required to overcome the internal resistance to get to the same charge. So in subzero weather, below zero etc, you want to see something closer to 15 volts or so. Buffalo aka "America's Strategic Snow Repository" has some cold weather iirc.
Start the engine in park and then turn on all the lights, heater blower and accessories to load up the alternator. Then spool up the engine to a fast idle to get some juice flowing. Measure the voltage at the battery posts. Should stay about the same 13.8 to 14.3 @70°F, the idle test won't tell you too much, but this will.
It's important that the grounds and positive cables are fresh, clean and shiny bright tight, clean electrical connectors and alternator itself has solid connection to motor with no corrosion. Even a little bit of invisible corrosion will cripple any alternator no matter how big, and the battery will be chronically undercharged. In an '84 just replace all the cables at block, frame, and firewall. Trust Me. Grind down to bright shiny metal at block and use something like 00 AWG cables with professionally crimped on tin washed copper terminals. They aren't all that expensive and work well. The el-cheapo generic cables sold in the blister packs are CRAP. They use thick insulation to make it LOOK like they are hefty, but they really aren't.
1) Was the battery fully charged before taking that reading?
With the truck off, not running, battery voltage is 12.5V. I tried running a dedicated ground between the case of the regulator and the alternator case as outlined in the test instructions, it didn't change anything. Then, as instructed, disconnected the voltage regulator connector and restarted the truck, testing voltage. I received regular battery voltage. Though now that I think of it, I'm not really sure how this test works because it seems I'm just taking the alternator out of the picture.
I'll attempt dedicated grounds and see what happens but could a faulty alternator cause and over charge condition?
13.8 to 14.3 is normal, and exactly what you want to see. 12 volt batteries should really be called 13 volt batteries. At least they are closer to 13 when at 100% charge and a serviceable battery will always read over 13 volts before the "surface charge" is removed.
So all of the accessories in the car will be receiving over 12 volts under normal circumstances? I thought for sure that it would somehow be regulated to only receive 12V or slightly over. Then again, maybe I'm basing that on the fact that I've always tested circuits with just they key on and engine not running. My biggest concern is the electric choke. With 14 volts, I just want to make sure that the heating coil doesn't burn out. Also, my ignition coil is at almost 10.5 volts with engine running. Seems high...
Originally Posted by Tedster9
Buffalo aka "America's Snow Repository" has some cold weather iirc.
Snow repository... I like it. First time I've heard it and I'll have to remember that LOL
Originally Posted by Tedster9
It's important that the grounds and positive cables are fresh, clean and shiny bright tight, clean electrical connectors and alternator itself has solid connection to motor with no corrosion. Even a little bit of invisible corrosion will cripple any alternator no matter how big, and the battery will be chronically undercharged. In an '84, just replace all the cables at block, frame, and firewall. Trust Me. Grind down to bright shiny metal at block and use 00 cables with professionally crimped on terminals. They aren't that expensive and work great. The cables sold in the blister packs are CRAP. They use thick insulation to make it LOOK like they are thick, but they aren't.
All of the cables are brand new. I used 2 gauge from the relay down to the starter, the rest are 4 gauge. I should check the firewall to block cable. I know it's there but it could be crappy.
OK, sounds like you are tracking then. Everybody always wants to leave those 30, 40 or 60 year old resistors, er, battery cables installed for some reason.
Automotive components are designed for a fairly wide tolerance range of voltages, mostly. They are called "12 volt" but that's just convention. Everything is going to see somewhere around 14 volts or more in real life.
Except the coil, maybe. You'll have to look into that. Depending on the era, many ignition coils were fed through a resistor wire to reduce the voltage (current, actually) the ignition was fed or could draw.
Here's some really good info on charging system checks and and a little "voltage drop" testing of the wiring and ground circuit. Smart that you're getting ready for winter now, ha ha.
Every year it's the exact same thing on the news. "Buffalo, NY, aka "National Strategic Snow Repository" has been digging out after a huge winter storm..." Then they show some poor SOB trying to shovel 8' of snow out of his driveway, etc, stuck cars. You'll be good to go, though!
Dnkensinger - It looks like you are on the right track. And you are getting good advice. But I'll throw my $.02 in as well.
It used to be that a fully charged automotive battery would show 12.8 volts. However, with the advent of batteries made for specific uses, like deep-cycle batteries, and differing technology, you can't really say exactly what the fully-charged voltage should be. But, somewhere between 12.5 and 12.8 volts is about right.
And, when measuring the voltage while running you need to do so at the battery, not in the cab. That's because the truck's wiring was marginal when new, and it is far from new. So, there is appreciable voltage drop across the wiring, connections, fuses, switches, etc And how much drop is dependent on the circuit and the load on it, but 1 to 1.5v isn't unusual.
As for the coil's voltage, the best way to measure that is with the key on but the engine off. You should see about 7 volts.
Well it seems like the voltage I am reading with the truck running is normal. I'm getting between 14.6-14.8 at the battery terminals. As for the coil, I guess that's a completely separate problem that I have to diagnose. Anyone have any experience replacing the resister wire? are there splice points that are specific as to not affect the resistance value?
Congratulations, your alternator is working properly. I wouldn't worry about the coil voltage unless the coil is overheating and cutting out. The ballast resistor is working and dropping voltage to the coil by a reasonable amount.
How do we know that? Has the voltage been reported? If he has the volt meter out he might as well run a simple test.
Originally Posted by dnkensinger
my ignition coil is registering almost 11 volts
From his information we know the coil is getting ~4v less than battery voltage. I have not found this to be a reliability issue with a factory Duraspark II coil.
In the same sentence he states the electric choke and wiper motor are getting ~14v, so clearly this is with the engine running, meaning at least a 4v drop to the coil based on his
Then we can't tell whether or not there is a resistor in the circuit. He's reading a voltage that is anything but a DC voltage on a DC scale. Here's what the waveform looks like, and the top of it goes to over 50 volts.
All he needs to do is check it with the engine off and the key on. Then we will know.
I will test the voltage with the engine off/key on, but I had only tested coil voltage with the engine running so far, and it is slightly above 10 volts. I'm just not used to seeing that high of a voltage at the coil.
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