Help - Alternator - Electrical smell
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Laughing Gas
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From: DC
Help - Alternator - Electrical smell
I replaced the alternator last night based on the following problem:
Battery light on with RPM below 800 or above 2000. Voltmeter was steady in the middle of the range.
Went for a test drive with my new (rebuilt) alternator. Worked fine for about 10 min, then battery light came on steady, volt meter pegged at 18v and headlights got much brighter. I figured the regulator died, so I got another alternator.
I replaced the alternator again. Ran the truck for about 5 min and started to smell electrical burning smell. So, I shut down and looked at wires and fuses. Nothing obvious. Any ideas? I'm posting this in the '97-'03 section too (I want to fix it tonite). Thanks.
Battery light on with RPM below 800 or above 2000. Voltmeter was steady in the middle of the range.
Went for a test drive with my new (rebuilt) alternator. Worked fine for about 10 min, then battery light came on steady, volt meter pegged at 18v and headlights got much brighter. I figured the regulator died, so I got another alternator.
I replaced the alternator again. Ran the truck for about 5 min and started to smell electrical burning smell. So, I shut down and looked at wires and fuses. Nothing obvious. Any ideas? I'm posting this in the '97-'03 section too (I want to fix it tonite). Thanks.
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Laughing Gas
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From: DC
Voltages were 13v off
15v running
I ran the truck for a few minutes again. Alternator got surprisingly hot for only running 3-4 min. Sure seems like a bad voltage regulator, but what are the odds of 2 in a row?
15v running
I ran the truck for a few minutes again. Alternator got surprisingly hot for only running 3-4 min. Sure seems like a bad voltage regulator, but what are the odds of 2 in a row?
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Laughing Gas
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From: DC
Let me add a couple of things since, per my Haynes, the off and running voltages are about normal.
It looks like the voltage regulator is doing it's job, otherwise I'd see much more than 15v at the batt when running, right?
Alternator getting hot could be a few things. 1. Failing mecahnically inside. 2. Huge amperage draw like in a dead short. But, I haven't blown a fuse. Can't find any wires getting hot (especially big ones). Alternator casing sure is getting hot though.
The first alternator had similar symtoms. Ran it for 10 min or so with no problems, and then steady BATT light and pegged voltmeter (as if the volt regulator fried). Strange thing is after it sat overnight, I started it and had no light and the gauge was normal, almost as if something happens when the alternator overheats.
I really want to believe I got two bad alternators (three if you count the original) but, a little voice says I have a problem somewhere else.
It looks like the voltage regulator is doing it's job, otherwise I'd see much more than 15v at the batt when running, right?
Alternator getting hot could be a few things. 1. Failing mecahnically inside. 2. Huge amperage draw like in a dead short. But, I haven't blown a fuse. Can't find any wires getting hot (especially big ones). Alternator casing sure is getting hot though.
The first alternator had similar symtoms. Ran it for 10 min or so with no problems, and then steady BATT light and pegged voltmeter (as if the volt regulator fried). Strange thing is after it sat overnight, I started it and had no light and the gauge was normal, almost as if something happens when the alternator overheats.
I really want to believe I got two bad alternators (three if you count the original) but, a little voice says I have a problem somewhere else.
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From: Virginia
It's disappointing sometimes, but 2 bad alt's in a row has happened before. You would think if you had a problem, all the alt's would have the same symptoms. It seems the new ones have different symptoms than the original.
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Laughing Gas
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From: DC
Thanks Dave. I hope you're right. I think I'll call the dealer tomorrow and see if they stock a new one. Won't be cheap, but it's one way to be almost certain that the part will be good.
Fleet Owner
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From: Easton,Ks
If the wire that leaves the "A" terminal of the regulator is not getting full battery voltage it may cause this, check to see if the "A" wire and the battery have the same voltage, this wire tells the alternator to charge or not to.
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Laughing Gas
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From: DC
Which is the "A" terminal on the alternator, is it the same as test point "A" on the back of the alt? Looks tough to get to. Do I do this test with the engine running or off?
I'll check the grounds too. Anyone know where on the frame I should look for the main neg ground. The wires are a little tough to follow. Thanks.
I'll check the grounds too. Anyone know where on the frame I should look for the main neg ground. The wires are a little tough to follow. Thanks.
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From: Where's my map???
Just follow neg. side of the battery cable down. It should connect to the frame about midway and then continue to one of the bolts that hold the starter in. Also check all other ground straps from motor to body/firewall.
Fleet Owner
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From: Easton,Ks
Originally Posted by Joe Finn
Which is the "A" terminal on the alternator, is it the same as test point "A" on the back of the alt? Looks tough to get to. Do I do this test with the engine running or off?
There is a plug on the alternator that you can pull out and one of the wires ("A") tell the alternator the state of the battery. You can check the resistance of this wire to the positive post of the battery and the voltage.
It would best test with the engine running but this may be hard to do and of course you can not pull the plug out with it running.
1996:
http://i54.photobucket.com/albums/g9...96Charging.gif
2005:
http://i54.photobucket.com/albums/g9...5FCharging.gif
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Laughing Gas
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From: DC
In theory, going from the A wire to ground should show the same voltage as the battery (~12.5 off or ~15 running). To check resistance, I go from the + on the battery to the A wire. How many ohms should I expect to see? I would suspect, that if the voltage reads good, the resistance will probably be good too. Sorry for all the follow up questions, but my electrical knowledge is somewhat lacking.
Fleet Owner
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From: Easton,Ks
Originally Posted by Joe Finn
In theory, going from the A wire to ground should show the same voltage as the battery (~12.5 off or ~15 running). To check resistance, I go from the + on the battery to the A wire. How many ohms should I expect to see? I would suspect, that if the voltage reads good, the resistance will probably be good too. Sorry for all the follow up questions, but my electrical knowledge is somewhat lacking.
Yes you should get the same voltage reading to ground at the "A" as you get at the battery + Term.
As far as ohms I would be looking for an open or a big voltage drop, a small ohm reading would be normal.
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Laughing Gas
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From: DC
Edit:
Just ran the checks.
12.5v battery to alternator housing
12.5v test point A to ground
0v test point A to the + side of the battery
As far as I can tell, there should be 12v from test A to the + side of the battery. Anyone have an idea of a common fail point or which wires I need to be looking at?
Edit: Just tested point F to ground - it read 12.5v. I think that means a bad voltage regulator, which takes me back to getting another alternator. My question is, would a fried voltage regulator cause the test point A to the battery + to fail?
12.5v battery to alternator housing
12.5v test point A to ground
0v test point A to the + side of the battery
As far as I can tell, there should be 12v from test A to the + side of the battery. Anyone have an idea of a common fail point or which wires I need to be looking at?
Edit: Just tested point F to ground - it read 12.5v. I think that means a bad voltage regulator, which takes me back to getting another alternator. My question is, would a fried voltage regulator cause the test point A to the battery + to fail?
Last edited by Joe Finn; Oct 26, 2006 at 06:32 PM. Reason: More info: