First time I've dealt with an alternator...

crw

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1,715
Location
Pocatello, ID
On my Lincoln Mark VIII, my son is now driving it to high school. (What a car to have in high school...!) He called saying the low battery light is on again. (Last week we replaced the battery.) I went up to measure it. No drop that I can see from the connections. I measure 12.29V with the engine stopped, and 11.9V with the engine running. If I set the probe right on the alternator, I get the same values. So, I assume it's got to be the alternator, right? Any tips? It looks pretty straightforward.
 
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19,686
Location
Sunny Florida
Remove the alternator and have it tested first. Most auto parts places will bench test it for free. At that age the car could have a number of other issues, but it would seem your diagnosis is good.
 
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253
Location
NJ
I have a Mark VIII. There is no low battery light, that light is a low voltage light. You tested a low voltage too, you should be seeing 14+ volts running. Time for a new alternator!
 

crw

Thread starter
Messages
1,715
Location
Pocatello, ID
Yeah, I believe it's a message on the screen that he is seeing. He also says that by the time he got to school the power was way down. I'm hoping he doesn't have a ton of homework, so I can have him work with me on the project, so he can learn!
 
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3,894
Location
missouri usa
Agree alt is the problem but to be sure they can test it for free at oreillys while still on the car and can test it off as well. The test off does tell more but I think your test shows its failed
 
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25,974
Location
Upstate NY
Originally Posted By: SrDriver
Remove it and check if there is a rebuild shop in your area before getting a rebuilt unit from auto parts.
Have you son tell people he plans on becoming a lawyer (The Lincoln Lawyer). Unsure if there is a ground wire to that alternator or the frame grounds it. Try a jumper cable (the black wire only) from the battery negative to the frame of the alternator and see if it changes anything. I agree rebuild shop first, if none around, then to a place thats tests them. I would go to a NAPA or Carquest before I would go to AZ or AAP. Rebuild shops seem to be a dying business or maybe there were just never that many around. When I went to one last week, he was busy and had tons of alternators & starters on the shelves. But a garage can call a NAPA or Carquest and have an alternator delivered in 30 minutes. Unsure how they deal with the rebuild shops.
 
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11,423
Location
Phoenix
Is this the vintage with the 3 prong plug that plugs into the voltage regulator that had some issues? I kinda remember this being one of the symptoms...going off memory here from a long time ago!
 
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5,653
Location
Central IA
Yeah the alternator should be putting out near 14 volts. As for the repair shop, if he offers some sort of warranty on his rebuilds then thats the way to go. We have one guy locally but he wont stand behind anything so we just had to start buying rebuilts from O Reillys. Nice thing about that is if ya get the lifetime warranty ones and do a lot of traveling, if the alternator goes out in any town with an O Reillys, you can get a free alternator if ya keep your receipt. Cant do that with a local rebuilder.
 
Messages
25,974
Location
Upstate NY
Originally Posted By: Robenstein
Yeah the alternator should be putting out near 14 volts. As for the repair shop, if he offers some sort of warranty on his rebuilds then thats the way to go. We have one guy locally but he wont stand behind anything so we just had to start buying rebuilts from O Reillys. Nice thing about that is if ya get the lifetime warranty ones and do a lot of traveling, if the alternator goes out in any town with an O Reillys, you can get a free alternator if ya keep your receipt. Cant do that with a local rebuilder.
True, but how many people have had problems with an alternator from a local rebuilder? I have 2 and neither one has blinked. People also need to keep in mind that the alternator is made to keep the battery charged, not charge a dead one. Dead batteries should ALWAYS be charged with a plug-in charger if possible.
 
Messages
5,653
Location
Central IA
Originally Posted By: Donald
Originally Posted By: Robenstein
Yeah the alternator should be putting out near 14 volts. As for the repair shop, if he offers some sort of warranty on his rebuilds then thats the way to go. We have one guy locally but he wont stand behind anything so we just had to start buying rebuilts from O Reillys. Nice thing about that is if ya get the lifetime warranty ones and do a lot of traveling, if the alternator goes out in any town with an O Reillys, you can get a free alternator if ya keep your receipt. Cant do that with a local rebuilder.
True, but how many people have had problems with an alternator from a local rebuilder? I have 2 and neither one has blinked. People also need to keep in mind that the alternator is made to keep the battery charged, not charge a dead one. Dead batteries should ALWAYS be charged with a plug-in charger if possible.
Well like I said, the local starter and alternator dude we used had a lot of comebacks. Just like with any business the quality of service and work varies.
 
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4,844
Location
Saskatchewan
Originally Posted By: Donald
True, but how many people have had problems with an alternator from a local rebuilder? I have 2 and neither one has blinked.
Between me and one of my buddies, my local rebuilder is 0 for 3. The last time I needed an alternator I bought a brand new lifetime-warranty Hitachi. But, unfortunately, a premium option like that isn't available for every vehicle.
 
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