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Discussion Starter · #1 ·
I have a 03 Excursion. Its a 7.3 and has about 213,000 on the clock. It runs really well and I believe she led a pretty charmed life before me. I have only owned it for the past 13,000.
Anyway the other day I was driving and the battery light came on. It quickly went out again. This has happened several times over the past few days.


  • The batteries are new interestates.
  • I had the alternator tested at the local Advanced and everything checked out ok.
  • I checked it myself with my OBD / Torque Pro App and it seemed to be putting out over 13v.
The other night I was leaving work and it was very cold. It seemed to do it then more than ever. The light almost looked like it was pulsing with the rattle of the engine.


On a possibly unrelated note I noticed when I was looking at the Torque Pro app that the coolanttemp was reading negative 40? Obviously something going on there. Dummy gauge on dash seems to be working ok.:sick:


Thoughts?


Thanks in advance
 

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The engine coolant sensor doesn't report back to the PCM, so that value is meaningless. Watch the voltage while the light is flickering. It's probably a pretty good sign your alternator is on its last leg.
 
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I have had a number of alternators that tested OK while they were just idling in a parking lot, but take them out on the road and they were junk.
 

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Discussion Starter · #4 ·
I had the scanner on it while I was rolling and it seemed to stick right around 13.1V I was looking at the alternator thats on it and its got a sticker on it " Made in China " ....maybe not so much on the quality..

Been so damn cold here...warming up this weekend may have some time to investigate further. Might just get a lifetime warranty one from Napa and change it.
 

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Before buying any parts, START at the beginning. No alternator will work if the battery terminals are junk. Click this & read all the captions:

 

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Discussion Starter · #7 ·
This morning I was on my way in and I hooked up the torque pro app to watch the voltage as i was driving. The light was more active than it has been. I was able to catch a few readings as it flashed. They were as low as 11v. I will check the battery connections but I just had two new Interstates but in and they cleaned everything as they put them in. I will check them for good measure because ya never know !
 

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Shops generally DON'T have their best technicians doing battery installs, so don't expect the job to be done right. Read all the details in those captions, and then inspect what you've got.
 

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I'd just replace the alternator at this point. If it's a chinese one or the original time to renew.

I'd also get an electronic gauge (Edge, scangauge, SCT, etc) on there to see exactly what kind of juice you're getting.

J
 

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Take a meter and start testing the connections from each battery.

Start out testing from post to post, not the clamps but the post.
Then from the ground post to the positive clamp, then to the other end of the cable.
A bad cable will give you very erratic measurements and cause problems when there are vibrations such as when you are driving down the road.
 

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Discussion Starter · #11 ·
I ended up buying a new (lifetime warranty) alternator from Napa. I put it in Saturday. I have not seen the battery light since. Hopefully that was the ticket. Thanks so much for all the input thus far.
 
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