Pulsing Lights

[BOWHNT]

Every light in the entire vehicle is pulsing. I don't think it's a random flicker but more of a steady rhythmic pulse. It only occurs when it is running. I've checked battery and ground connections. Is this sounding like an alternator problem to you guys? Is there a way to diagnose?

Brad

 

[df2x4]

My '97 K1500 Suburban does the same thing these days (mainly on cold starts), I think it's the voltage regulator on the alternator going out.

One thing to be aware of though, even if your connections look OK there could be corrosion inside the jacket of the wire that you can't see. My Suburban's lights were pulsing really bad at one point and replacing the old internally corroded positive battery cable fixed it completely for quite a while.

 

[Schurkey]

Put a voltmeter on the battery. Check voltage.

Put the voltmeter on the alternator. Check voltage.

Compare the two readings. Should be within 1/4 volt (or less) of each other.

Is the battery discharged? Unable to hold a charge? Have you load-tested it?

As said, verify cables and connections for corrosion or poor contact.

 

[BOWHNT]

All good suggestions guys, thanks. Is there a way to test the output of the alternator? Can places like O'Reilys or Autozone test it?

 

[Schurkey]

All good suggestions guys, thanks. Is there a way to test the output of the alternator? Can places like O'Reilys or Autozone test it?

They can, but it's a nearly-worthless test.

The better way is to test the entire electrical power team--battery, alternator, regulator, starter, AND THE WIRE HARNESS THAT CONNECTS THEM. "On-the-car" testing is far more comprehensive than "Off-the-car" testing.

Off-the-car testing of individual parts makes it easy to miss problems.

 

[BOWHNT]

Just to follow up, I installed a new alternator yesterday and that solved the problem. All good now. Also, replaced the idler and tensioner while I was at it. Man, the old ones were rough. Much smoother and quieter now.