2003 grand marquis voltage guage fluctuates from @ middle to almost pegging the high side. New battery and alternator; old alternator does not flucuate but only puts out 11+ volts. Wrong alternator ?

Asked by Apr 04, 2017 at 05:33 PM about the 2003 Mercury Grand Marquis LS Premium

Question type: Maintenance & Repair

We tried an alternator from a 2000 merc and it caused similar voltage
flucuations as the one we have now...the two are different part no.s.\could this
be an amperage issue and would that cause a voltage fluctuation.
Is there something else to look for ???

3 Answers


check all grounds and or have it VATED...starting ...charging...load tested..sometimes this is a free service..and the voltage reg..diode check/alt.


Basically a Ford product. It has a voltage regulator in the rear of the alternator you can check and replace. Pretty cheap part to buy.

What is "VATED"...the problem is sporadic....usually after the car is run for 5/10 minutes ...this is a rebuilt alternator that bench tested ok...could the amperage be a problem if wrong alternator

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