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Alternator R&R 2004 Deville

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The Friday before last, my wife called me and said her 2004 Deville wouldn't start.  A friend of hers drove her home and when I got home from work, we took the Silverado (along with tools, battery load tester, tow strap, etc. with us) to the doctor's office where the car left her.

I opened the door and the interior lights were about half the normal brightness so I hooked up the jumper cables and got it started.  When I removed the cables, the car died   after a few seconds.  A repeat procedure and leaving the cables hooked up for five minutes allowed the car to be driven home but the "battery volts" display on the DIC would only exceed 12.6V if I revved the engine.  At highway speeds, the battery voltage was normal - 14.7 V but would drop at idle until everything warmed up.   I put the charger on it and after a couple of hours, the battery was fully charged. 

The starter and alternator shop I use told me that was a symptom of a failing diode.  Before pulling the alternator, I checked the output with my oscilloscope and did not see any negative component on the waveform although it was low - 12.2 V.

I checked the signal on my 2005 Deville and it was identical except it was 14.7V, not 2V lower.  I decided that I was going to have it rebuilt so I began to see what was involved in removing the alternator.  The shop manual says to remove the radiator and associated oil cooler lines..  Looking at it, I decided NOT to follow the shop manual procedure.  There are enough slack in the cooling hoses to slide the radiator and condenser forward.  With the airbox out of the way and the cross car brace removed, it was not that bad of a job to remove the fans.  Once the fans were out, it was a quick job to remove the alternator.

The rebuilder called me to inform me that the terminals of the voltage regulator were the problem.  Apparently, one of the terminals was not welded which would result in the intermittent charging until the car warmed up.  Must have been a factory defect with the Nippondenso alternator.

I had the shop rebuild the alternator and all was well after I re-installed it the next night.

The biggest problem was removing the fans - the housing interfered with the radiator hoses but it can be removed without removing the radiator (and oil cooler lines).

It was unfortunate that the factory procedure was so involved when the previous generation Deville had an access panel that when removed, allowed the alternator to be remoded from the bottom in less than a half hour.


'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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