Weird alternator woes
02-06-2003, 10:24 PM
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Weird alternator woes
My truck is pissing me off. I had my alternator tested and batteries tested and they are both good. Then I thought the volt regulator went bad so I replaced my PCM and then I figured out all I did was blow my alternator fuse. Now it is acting up, but at least it is driveable. When I crank it up the battery charge gauge or whatever is always real low and the check gauges light comes on. Then when I get going it gets back up to 15. And sometimes when I let it idle it goes down to like 13 or so. Is something draining it? I have no idea. What do yall think?<br>
02-07-2003, 05:19 PM
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Re:Weird alternator woes
Have you put a voltage tester on the truck to varify that the Alt is actually charging correctly?<br><br>Also, check for bad or broken ground wires.<br><br>Good luck.<br><br>Rich
02-07-2003, 07:38 PM
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Re:Weird alternator woes
If the alternator was tested, it should be putting out 14+ v at idle. Should never drop below 13.8, except on very heavy loads like the grid heaters (may have problem there). Just a guess, but sounds like a bad rectifier in the alternator. The alternators on the diesels are a high output type, so a typical parts/battery store may not have realized it was not producing full rated current. If you have recently jump started the truck, I'd be even more suspicious of bad rectifiers.<br><br>just my .02...<br>Good luck,<br>-Scott
02-07-2003, 08:26 PM
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Re:Weird alternator woes
When I bought my truck "used" it was acting up also. I had the batteries checked at a auto parts store but they did not dissconect the two batteries. They said my alternator was bad. So I took it off and had the local alternator rebuild shop rebuild it. The brushes were worn out, but this didn't fix my problem. Then I took the batteries off and had them checked, one had a bad cell in it. This fixxed my problem hope you get it straightened out. This was a pain in the a...s for me also.
02-09-2003, 10:36 AM
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Re:Weird alternator woes
Check your crankshaft position sensor wiring and connections, also the sensor and check for excessive grease or oil on it. To adjust it you will need a brass feeler gauge.
02-11-2003, 01:43 PM
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Re:Weird alternator woes
Do you mean my crank speed sensor? My rpms and speedometer gauge act up every once in a while. I might need to replace this, but I just replaced my rear wheel speed sensor. So I will probably replace this crank sensor too I guess.
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12-07-2004, 05:29 PM
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Just reading this thread- it's not the exact problem that I have but close! Over last 3 months replaced both batteries and now the alternator. Truck is not hitting more than 13.10 to 13.5 (on a Snapon/Bluepoint meter), mostly it's around the high 12s. I have the meter wired to the cigar plug and sitting on the seat next to me while I drive. It's strange because I'm seeing the highest volts in the AM when I head out for work!? Turning on headlights/fan etc dont make a dent in the volts- it holds steady with the extra load!? Strange?
BTW the dashboard voltmeter is completly off compared to the Snapon meter. Whats with the PCM- manual says to not touch it- nothing about trouble shooting it. HELP!
BTW the dashboard voltmeter is completly off compared to the Snapon meter. Whats with the PCM- manual says to not touch it- nothing about trouble shooting it. HELP!
12-08-2004, 03:11 PM
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I had the same problem on my 96. I rebuilt the alternator replaced the rectifer and replaced the brushes as well. There is a problem with the rectifer ground. I you look at the back of the alt there is a aluminum cover that is held on by 3 nuts. Remove and drill out the hole were the the rectifer ground stud is so you can get a good connection with the nut on the rectifer ground terminal then install the cover and the two nuts to hold it on. I also tested my batteries they seemed ok but I changed them out at the same time.Now every thing is ok, I have super bright lights and it is charging at 13.5 with eveything on.
12-08-2004, 05:18 PM
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Jack- Thanks- But I replaced the alternator with a new rebuilt unit from NAPA. Today (with the new altr installed) I saw volts go all the way to 13.8! The mechanic at work said it was the PCM that was at fault- he said to give it two days to "relearn" with the new alternator, that seemed like good news untill... tonight driving home with the headlights on I saw the volts crash down to the low 12s! I think I was lucky to make it back home- the lights were getting real dim and the GEN warning light came on!
Unless you guys have another idea I guess I'm headed to the dealer...the mechanic said they (the dealer) would have to service PCM.
BTW mine is a 1997 2500 CTD (4X4)
Unless you guys have another idea I guess I'm headed to the dealer...the mechanic said they (the dealer) would have to service PCM.
BTW mine is a 1997 2500 CTD (4X4)
12-09-2004, 09:31 AM
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How old are your batteries? Have you had trouble starting in the morning. like I said earlier I also changed my batteries as well. I had the same problem as you.
12-09-2004, 10:13 AM
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possible defective alt,i know it's a rebuilt but,anything can happen.More than likely voltage reg in computer is on the bum.If i remember corectly hauling has a fix for that.Just my .02
Luc
Luc
12-09-2004, 04:17 PM
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Yes you can wire up an external voltage reg. Yes it was haulin in dixie who posted the how to (thanks!) Here is the post:
https://www.dieseltruckresource.com/...=36421#newpost
https://www.dieseltruckresource.com/...5&pagenumber=1
Here is another post that may be of help:
http://www.turbodieselregister.com/f...threadid=41593
Good luck, Kevin
https://www.dieseltruckresource.com/...=36421#newpost
https://www.dieseltruckresource.com/...5&pagenumber=1
Here is another post that may be of help:
http://www.turbodieselregister.com/f...threadid=41593
Good luck, Kevin
12-10-2004, 01:17 PM
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Hats off to 1st Cumnz! Not only was the NAPA rebuilt bad- it WAS A DISASTER! While driving on the highway Thurs morn (second day with the new one) I lost all alternator output- then the temp gauge pegged all the way over...the fault...the pully on the "new" alternator started to come off the alternator- it then threw the belt causing the truck to overheat (lost the water pump)!
So a BIG WARNING to everyone- check those new or rebuilt parts- they may not be what they seem!!!!!
So a BIG WARNING to everyone- check those new or rebuilt parts- they may not be what they seem!!!!!