High pitched whine and headlights flicker

[Fardringle]

I have a 2006 Dodge Durango that recently started developing a strange problem. Once in a while I can hear an intermittent high pitched whine that almost sounds like a morse code message from an old war movie. When it happens at night so that I can see the headlights, I can see that the headlights and dash lights flicker slightly in the same pattern that the sound changes. It doesn't seem to change based on engine RPM or speed or by turning the wheel. I haven't ever heard it happen at highway speed, but that is probably because I just can't hear it over the road noise since it is pretty quiet.

Any ideas what this might be, or what I can test to narrow down the cause?

 

[C1]

What would fit the bill for the problem description is that some activated electrical component is the source. A motor of some kind would fit the bill as something like that would have the needed current draw to flicker the lights as well as provide the mechanical clicking source independent of the rest of the car (ie, engine & road travel).

With the car at idle (and the issue exhibiting), open the hood & even the trunk lid and listen for the source of the sound. Listen also to the interior.

Possible sources are the electrical cooling fan under the hood or an HVAC fan behind the dashboard.

A possibility is to begin pulling fuses to deactivate electrical circuits in attempt to locate at least the circuit involved. After that, investigate to determine candidate electro-mechanical devices on the subject circuit which could be the cause/source of the issue.

 

[Fardringle]

I have tried listening from inside but couldn't find the source. Part of the problem is that it only happens once in a while so I can't just start the car and have it be there whenever I am ready to do some troubleshooting. I will check under the hood if there is a safe place for me to stop the next time I hear the sound. Thanks.

 

[mindless1]

I'd get one of those cigarette lighter outlet LED voltmeters and watch what the voltage is doing when it happens. Offhand I'd guess your alternator is probably going out, then with wonky voltages, it's hard to say whether some powered component might make strange noises but the headlights seem to be an indication that voltage is dropping.

Another thought is that you may have a power powered amp that is failing, possibly one with an intelligent power-on circuit so that you don't necessarily have to have the radio on for a fault to cause a massive current draw? Since the problem isn't happening more often, you might have to unplug the amp for a while to see if it goes away.

Any other (motor) with enough of a short to make headlights flicker, I'd think the motor no longer works. Small motors and solenoids, should blow a fuse then the problem doesn't come back after going away because the fuse is blown. Larger motors, there aren't that many in a typical truck, just radiator fan and HVAC blower, presuming it doesn't have electric power steering but you should notice steering or HVAC blower struggling while it happens, or temperature rising if the radiator fan failed.

Another thought is you might have a battery saver type circuit and the relay for that is failing, though I would HOPE that they designed that circuit so a fault can't cause loss of headlights while driving which is a pretty big safety hazard.

 

[FeuerFrei]

Alternator bearing going bad?

 

[bruceb]

Your alternator is dying. Have it checked at a place like Autozone

 

[Fardringle]

I appreciate the suggestions, and will have the alternator tested to be sure. But it looks like it was something stupid. (Mostly me being stupid and not actually looking under the hood before asking for suggestions. )

The battery terminals were badly corroded and the positive cable was actually slightly loose with a layer of corrosion building up between the cable clamp and the battery terminal. I cleaned those and tightened the clamps Sunday night and haven't heard the noise or seen any flickering since then (so far). That doesn't guarantee it's fixed since it was intermittent, but since that definitely could have been the problem, I'm hoping it was the only problem...

 

[FeuerFrei]

That reminds me. My car's clock has been resetting itself, a couple times now. I bet the battery terminals need cleaning.