dimming lights 03 z71

[snh34]

I have an 03 z71 and the head lights and dash lights dim at idle only when it is cold weather. What would cause lights to dim? Also the voltage gauge fluctuates when this happens.

[jyount]

Originally Posted by snh34

I have an 03 z71 and the head lights and dash lights dim at idle only when it is cold weather. What would cause lights to dim? Also the voltage gauge fluctuates when this happens.

sounds to me like your alternator is not keeping up at idle, I don't know how cold weather affects though. Alternator output is turned on, ramped up, etc by the bcm, It would probably work or not though. Maybe the cold weather aspect is because of having the blower on or something, who knows. Is your battery weak at startup when its cold? My wife's trailblazer kind of exhibited this a little last fall, then last winter I had to put a battery in it.

Pull it out and have it load tested, maybe the alternator just can't make up for the battery being a little weak.

[ukrkoz]

check belt tensioner gauge.
otherwise, sounds like alternator is going south. make sure you do not have, by oversight, some electricity chugging or power taking appliance on continuously, like a/c. though, on mine, i can have everything on, including seat heaters, and no problems.

[j cAT]

Originally Posted by snh34

I have an 03 z71 and the head lights and dash lights dim at idle only when it is cold weather. What would cause lights to dim? Also the voltage gauge fluctuates when this happens.

the first thing to do is check the battery connections/clean the connections....

with a volt meter what is the voltage when cold at idle....at about 40deg. F It should be 14.75 approx...

because of the intermittent nature after cranking I suspect the connections...the other very important thing to check is the ground connections through out the vehicle...many have had these poorly installed connections at the factory create many wierd electrical issues..

LOAD testing the battery at a service /battery supplier will determine if your battery is loosing its power/internal failure..

If the alternator did this issue that you have hot/cold then the alternator would be most likely be the problem,, and the voltage output would drop as all the loads would drag the voltage down to less the 13 volts...

with the engine running and all lights/ac on , alternator should put out 66-70 amps...voltage should be 14volts approx..engine at op. temp..

If you have aftermarket high current electrical equiptment all this info would not apply..