SureTrack Community Fix: Pulsing, Whining Suburban

Real Fixes from the Snap-on SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is currently available free with the purchase of a current Snap-on® diagnostic software version.

Replacing parts more than once is a real time waster for shops and frustrating for customers. Unfortunately not all new or rebuilt parts hold up as they should. SureTrack community member Ourfamilygarage had a Chevy Suburban in the shop that the alternator had been replaced in the past and now had symptoms indicating it had a problem again as well as a tricky noise problem. They posed their question to the community, and with the help of fellow community members mwk6503, ericsautomotive and others, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

Vehicle
2008 Chevrolet Suburban K1500 5.3L

Title
Whining from radio, pulsing headlights, replaced alternator and speaker.

Complaint
Customer complains of whining noise from radio and headlights pulsing.

Diagnostic Steps Performed/Parts Replaced
Radio has been making whining noise for few months. Alternator and battery were replaced, alternator was warrantied also. Headlights recently started pulsing while driving or revving the engine at idle. Checked IGN 1 voltage on scanner and it varies from 12.8v up to 14v but lower voltage does not correspond to the dim lights. What could cause these symptoms?

Best Answer from Community Members mwk6503 and ericsautomotive
ericsautomotive wrote: This just screams “Bad replacement Alternator”, Test the ripple coming form the alternator! AC voltage from a bad diodes can drive this DC vehicle crazy!

mwk6503 wrote: Agree with Eric’s, of course with AC ripple test. Make sure and set DVOM to AC current and test directly at alternator charge back wire with engine at 3000 RPM. Should be no more than .5V.

Cause
Swapped alternator out with another brand lessened the whine but was still present. Cleaned battery terminals and block ground, whine still present. Listening at the doors, the passenger side was a lot louder, unhooked the A-pillar Bose speaker and whine is gone.

Correction
Replaced alternator and passenger side A-pillar tweeter speaker.


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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.