Charging issue or light issue?
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Freshman User
Joined: Dec 2006
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From: Hewitt, tx
Charging issue or light issue?
I got lucky and found my grandpa's 1980 f100 custom with a 302 3 speed for sale. my grandpa had the truck from 1982 to 2004 when he sold it. It is pretty much exactly as it was when he sold it, except some one converted it to a floor shift. I plan on converting it back to column shift if I can find a good column or the parts to fix the original. I am so happy to have it back in the family!
now for my issue I have been fighting What appears to be a charging issue. the amp light is always on. I took the alternator and had it checked and it passed. so I replaced the voltage regulator but the light is still on. I thought I tested it right with a volt meter and got no change in voltage. but I did notice that with my test lamp on the battery it got brighter. so I was just going to replace the alternator next. but then just for fun of it I unhooked the battery while it was running figuring it would just die. but it didn't it kept running. so now I am baffled. is it a charging issue, a wiring issue, or a light issue. any ideas would be apreciated. thank you nathan b
now for my issue I have been fighting What appears to be a charging issue. the amp light is always on. I took the alternator and had it checked and it passed. so I replaced the voltage regulator but the light is still on. I thought I tested it right with a volt meter and got no change in voltage. but I did notice that with my test lamp on the battery it got brighter. so I was just going to replace the alternator next. but then just for fun of it I unhooked the battery while it was running figuring it would just die. but it didn't it kept running. so now I am baffled. is it a charging issue, a wiring issue, or a light issue. any ideas would be apreciated. thank you nathan b
Laughing Gas
Joined: Nov 2010
Posts: 924
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From: Johns Creek GA
Good job on getting Grandpa's truck back. I'm guessing your grandfather has similar tastes in trucks to mine, as I am now driving my grandfather's 1980, although it's an F-150 with the 300-6 engine.
I had a problem similar to yours in the course of dealing with my truck's electrical problems. It turned out that both the alternator and the voltage regulator were shot (the truck had sat for most of 15 years when I got it, so there were a lot of issues like that) when I got it. At one point, after I had replaced both the voltage regulator and the alternator, the truck was charging just fine, but the CHARGE light wouldn't go out - at least, not until I got the truck up to 45mph or so.
The culprit turned out to be the aftermarket (NAPA) voltage regulator I'd put in. I went online and ordered a proper Motorcraft replacement, and once I dropped that in the problem went away. So if you're running a parts store regulator, you might consider replacing it with the real thing.
I had a problem similar to yours in the course of dealing with my truck's electrical problems. It turned out that both the alternator and the voltage regulator were shot (the truck had sat for most of 15 years when I got it, so there were a lot of issues like that) when I got it. At one point, after I had replaced both the voltage regulator and the alternator, the truck was charging just fine, but the CHARGE light wouldn't go out - at least, not until I got the truck up to 45mph or so.
The culprit turned out to be the aftermarket (NAPA) voltage regulator I'd put in. I went online and ordered a proper Motorcraft replacement, and once I dropped that in the problem went away. So if you're running a parts store regulator, you might consider replacing it with the real thing.
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From: Hewitt, tx
Thank you at 45 dollars for the alternator I guess i will go ahead and replace it to may sure it is good and then look at the regulator. better safe then sorry when it comes to the charging issue! an interesting part about the truck is that it was purchased new by the montgomery wards company as a service truck. my grandpa bought it from them in 82 when they canceled their service program. it only had 1500 miles on it and he got it for less than half the cost as they were trying to get rid of them. since then he had put almost 300,000 on the original motor (that has been rebuilt since he sold it).
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From: Hewitt, tx
ok update. I replaced the alternator and now with my multimeter on it I am getting almost 14 volts. but the stupid light is still on. I put the old regulator back on it and the voltage was around 13.7, so lower than the new one but i did see the light go off or a minute. so I have decided that before I start driving the truck full itme i am going to install one of the three gauge setups so I have a mechanical water and oil pressure gauge and a volt gauge. i quess it is the racer in me that perfers the mechanical gauges over the electrical.
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From: Virginia
Check the "I" wire going to the regulator. That's where the light wire goes.
With the engine off, unplug the regulator plug. Turn the key to run but not start. Does the light still come on? Then go ahead and start the engine and see what the light does. If the light goes off with the regulator unplugged, I agree there is something wrong with the regulator.
With the engine off, unplug the regulator plug. Turn the key to run but not start. Does the light still come on? Then go ahead and start the engine and see what the light does. If the light goes off with the regulator unplugged, I agree there is something wrong with the regulator.
Moderator
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From: Virginia
If the system charges with everything hooked up(sound like it does if you get 14v or 13.7v) and the light still stays on, there must be a fault with the regulator. If everything is ok, the regulator puts 12v on the "I" terminal, and the light goes out, since the other side of the light is fed by the keyswitch. So that puts 12v on both sides of the light, and it does not burn.
If there is a fault with the system and it does not charge, the "I" terminal is close to zero volts, so the light has 12v on one side and near zero on the other, it lights up.
Since your system is charging, and the light is staying on, there must be something wrong with the regulator like a previous poster mentioned.
If there is a fault with the system and it does not charge, the "I" terminal is close to zero volts, so the light has 12v on one side and near zero on the other, it lights up.
Since your system is charging, and the light is staying on, there must be something wrong with the regulator like a previous poster mentioned.
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Post Fiend
Joined: Jul 2004
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From: Northern California
The signal to the charge warning light in the dash is operated by the regulator, so unplugging it would not help you diagnose a charge problem, but it may help you diagnose a problem with the regulator in refference to the light staying on.
Some parts stores can test the voltage regulator with their test equipment.
Some parts stores can test the voltage regulator with their test equipment.
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Freshman User
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From: Hewitt, tx
update. the truck is still charging at around 14 volts. I had my meter on it today and and I unplugged the indicator line and it stop charging. is this normal or can that be part of my problem. if I grounded the wire it would start charging again.
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From: Virginia
The indicator line from the cluster is what brings the alternator online to charge with a signal from the indicator which is fed from the keyswitch. So yes, that is normal, it's working correctly.
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From: Virginia
Be careful taking the light out. It won't work then, unless it has the resistor still in it. Ford usually put a resistor across the bulb, in case the bulb burned out, the charging system would still work. Without the resistor, a burned out bulb will kill it. So look for the resistor, sometimes it's located in the bulb socket itself. So it that's the case, unplug the socket, pull the bulb out, and then put the socket back in to retain the resistor.
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