Alternator Fuse?
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Freshman User
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Alternator Fuse?
Hey fellas, I was driving home tonight and I turned on my lights, it was dusk. when it started to get darker I was wondering if my lights were even on. the radio started to fade off and the interior lights got dimmer and dimmer, i couldnt see a thing, eventually the interior lights and accessories all went out but the headlights were still dim, I made it to my street and a cop pulled me over and after explaining what happened he lit my way home for me. I have been thinkin that maybe my alternator was going bad before, i have a draw on my battery and have heard that sometimes the alternator will draw your battery dead. (?) Well it wasnt working tonight, I was wondering if there was a fuse for the alternator or anything else I should check before replacing the alternator, one time I bought an alternator for a dodge truck just to find out the alternator fuse was blown. Do these ol bullnose have anything like that I should check be fore replacing the alternator?
Senior User
Joined: Mar 2006
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From: Windsor Ontario Canada
check battery terminals then check positive cable from battery to soleniod running voltage should be 14.2 if its higher battery may have a dead cell or be sulfated,if its lower i would remove alternator since they are easy to acess and test it depending on the year the voltage regulator may be part of the alternator. best luck
pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
There is a fusible link connecting the alternator output to the starter solenoid.
If you have a 2G (internally regulated) alternator, be sure to replace the charge plug pigtail before replacing the alternator itself.
If you have a 2G (internally regulated) alternator, be sure to replace the charge plug pigtail before replacing the alternator itself.
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i guess i should have told you that i have an 82 f350 i dont know if that will help or not, i will check the fusible link, battery is good, all connections to the solenoid are good, I will check the voltage on it this afternoon- not too worried about replacing the alternator they are pretty cheap but would rather not spend the money if I dont have too. have you ever heard of the alternator causing a draw on the battery? it sounds feasible but dont know if its legit.
pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
Yes, of course a failed alternator or regulator can drain the battery.
If it is an '82 I'd expect it has a 1st generation alternator with an external regulator mounted inside the fender.
Does it have multiple wires bolted to the back of the alternator, or just two plugs?
There are three diodes inside the alternator that act like one way valves for the electricity it produces.
If any of these fail, power from the battery will flow backwards when the engine is off.
Does the back of the alternator feel warm?
Will the battery cable spark if you disconnect or re-connect it?
If it is an '82 I'd expect it has a 1st generation alternator with an external regulator mounted inside the fender.
Does it have multiple wires bolted to the back of the alternator, or just two plugs?
There are three diodes inside the alternator that act like one way valves for the electricity it produces.
If any of these fail, power from the battery will flow backwards when the engine is off.
Does the back of the alternator feel warm?
Will the battery cable spark if you disconnect or re-connect it?
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i always disconnect the battery when its off because it will drain overnight if left connected so ive never left it connected to check for a warm alternator. I have an external regulator mounted on fender, there are two cables on the back of my alternator, there is no spark when connecting or disconnecting batt. the regulator is loose but has been for a while, dont know if this played a factor or not.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 38
From: EXTREME southwest CT
The regulator needs a clean, solid ground to work properly.
Leave the battery connected for a 1/2 hour or so and check if the alternator is warm.
This is not a fool proof test. But if it heats up it is pretty sure to be bad.
You can also bring your alternator to most major auto parts stores to be tested.
If it checks good then you have the joy of tracing a short somewhere else in your harness.
Leave the battery connected for a 1/2 hour or so and check if the alternator is warm.
This is not a fool proof test. But if it heats up it is pretty sure to be bad.
You can also bring your alternator to most major auto parts stores to be tested.
If it checks good then you have the joy of tracing a short somewhere else in your harness.
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Freshman User
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are you talking about the joy of finding a short to solve the batt draw problem or the loss of electrical power i experienced? I connected the battery for about 45 min and the alternator never warmed up, would a bad regulator cause a problem with the battery not charging?
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yeah I have both, but my multimeter only tells me voltage, maybe, I dont know how to change it to test milliamps if I even have that feature available on it, Im just going to pull out the alternator and have it bench tested. I properly mounted the regulator so that it would be grounded before checking for a warm alternator.
pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
A multimeter has 'multiple' modes. Ohms and voltage probably being most useful in this case.
Connecting the regulator ground would not affect the battery drain if it were the alternator at fault.
Let us know how it checks out.
Connecting the regulator ground would not affect the battery drain if it were the alternator at fault.
Let us know how it checks out.
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ok so here is what I did, I took out the alternator and had it bench tested, it passed, i was kind of hoping it failed, but it passed, I asked if they could check for a bad diode and they said the machine couldnt test that, but if the back of the alternator was warm that would be a hint. I guessed it must be the regulator then, so i bought a new one and replaced it, I ran it with the high beams on and the radio and heater full blast for about ten minutes, the lights never dimmed or anything, what I need to do is check the voltage on the battery before and after, I will do that tomorrow. thanks for your help guys i will keep you posted.
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Ive got some good news gentlemen! I left the battery connected all night and have not lost charge! the new regulator solved my battery draw problem as well. The voltage of the battery before running the engine was 15.04 then I ran it and during operation the voltage was 17.02 after the engine was off the voltage was 15.84. These numbers seem a little high to me but it is working how it is supposed to now with no draw! it has had a draw on it since last july. thanks a bunch for your help guys, ardwrkntrk you gave me a lot of good info.