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Voltage fluctuation

5K views 4 replies 3 participants last post by  ERIC PATTERSON 
#1 ·
Hello all. I have a 2006 2.4L and I have a strange voltage fluctuation. Lights dim. All lights. Heater blower fan speed changes. Radio dims. And the amp meter needle moves between 12 and 14.5 volts while this happens. I have replaced the battery and alternator. Both are brand new. Also the amp meter takes about 3 seconds at first start up to actually read any volts. Any suggestions. Hopfully it's not the PCM. I really don't wanna spend 600 bucks.
 
#2 ·
Was this problem occurring before you replaced the battery and alternator and you were trying to solve the problem by replacing them?

I am not certain if this models alternator is PCM controlled or not. If so that could be the issue so it is a good idea to figure that out first. Otherwise it is possible that you have a poor ground or corrosion on the power side of the electrical system somewhere, the latter issues could be tested by voltage drop testing. Seeings how it is all things electrical I would start with the main power supply sources (alternator, battery, battery +/- cables, wiring to fuse box).

While the problem is happening I would suggest voltage drop testing with a volt meter from the battery (-) post, not the terminal but the post itself, to the alternator case, the engine block, and a body ground or two and see what readings you get. Ideally it should read very close to zero volts.

Then do the same from the battery (+) post to the alternator (+) post and to the fuse box main power wires. Again, should be reading close to zero volts.
 
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