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Q: lights flicker turn a/c or heater on and rpms fluctuate bad on 2004 Oldsmobile Bravada

all my lights flicker while driveing or idle. when i let off the gas or push brakes head lights dimm to almost off. also when i turn on the a/c or heater there is a loud click in the dash and the rpms drop almost to 0 and then jumps over 1000. this happens about every 30-40-sec. while turned on and the engine runs a litle rough while there on also. spent hundreds trying to figure it out no one can cause the check engine light never comes on. now it sucking more gas due to what feels like power loss. but no check engine light...HELP!!!!!
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Your concern sounds like an electrical supply issue, such as a weak alternator or voltage regulator. I believe the regulator is internal to the alternator, so in the end, you would likely just replace the assembly. Have your charging system checked, starting with the battery. A weak battery or one with a bad cell can also cause electrical fluctuations as you mention.

The reason I lean towards the charging system is because any time you create a load (such as turning on the heat - one of the most intense loads on your entire vehicle...), your vehicle stumbles. This could be because the heat is drawing so much power from your electrical system that even your engine's computer cannot keep up.

Good luck!
thanks i was leaning towards that my self. but with these newer vehicles and all the electrical stuff they have its hard to diagnose unlike the old vehicles where everything i simle.
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