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I have an electrical problem with my 96 Jeep Grand Cherokee. The alternator whines and the battery gauge drops to zero. I put a new battery in and a new alternator and it didn't fix the problem. any advice?

  • Have you checked and/or replaced the alternator belt? It's also worth checking the battery connections and the wiring to the alternator... – Nick C Feb 25 '15 at 11:09
  • When does the battery gauge drop to zero? All the time? Occasionally? Only when it whines? – HandyHowie Sep 24 '15 at 21:40
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You need to inspect the following:

  • Serpentine belt (actually, change it if you haven't done so already)
  • Tensioner pulley - While the tensioner may appear as though it's good, it may not be giving the belt enough tension so it has traction on the accessories.

One of the two is going to be your issue. There is the outside chance you received a bad alternator.

  • Also a good idea on the Serpentine belt, as you then have a good emergency spare. – Anthony Horne Jul 27 '15 at 7:06
  • I agree with Paulster... Those need to be addressed before looking at the alternator – Dee Jan 26 '16 at 1:52
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Are you sure it's the alternator that's whining?

Check your connections the Field plug on the alternator and the alternator to battery cable. There should never be zero volts coming out of the alternator. It will always be battery voltage or charging voltage. Test voltage at the battery. then at the alternator if the alternator show charging voltage there may be a blown fusible link.

If the volt meter on your instrument cluster shows zero the cluster/gauge may be bad. Or there is a problem with the serial data line between the cluster and PCM. Or there is a problem with how the PCM is receiving input voltage, probably from the ASD relay or similar.

  • Is the voltage regulator external on this? – Dee Jan 24 '16 at 2:52
  • Most late modal vehicles have internal voltage regulators. On this car that's a yes. – Ben Jan 25 '16 at 23:05
  • So if the voltage regulator is external he may want to check that. – Dee Jan 26 '16 at 1:25
  • Woops. I meant on his car the voltage regulator is internal. My mistake. – Ben Jan 26 '16 at 1:47
  • Ok... The Whiny alternator tells me the power has interference somewhere... Either on the connection to the alt itself the ground or the plug in wire. Please check that it hasn't fried. Sometimes people put battery on backward and just those seconds can fry the wire. – Dee Jan 26 '16 at 1:50

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