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Q: Car isn't generating enough electrical power t run all the accessories

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I bought the car new and have complete maintenance records. YourMechanic has done most of my maintenance for the last year. Problem started this past winter. When sitting at a light with the car idling, the headlights/dash lights dim noticeably. If the A/C is also running, the stereo will shut off. Sometimes the a/c compressor will cycle on/off repeatedly. By throttling the idle up to about 1500rpm, I can keep everything normal. I have replaced the alternator (YourMechanic), battery and fuses problem persists. I'm running out of ideas...

My car has 236500 miles.
My car has an automatic transmission.

A: Hello. Assuming the alternator and battery ...

Hello. Assuming the alternator and battery do indeed check out completely OK (they can be tested using the usual procedures), the problem you are experiencing is due to substantial unwanted high electrical resistance (in turn due to a broken wire, corrosion on a ground lug, loose terminal, maybe in combination, too). The high resistance causes a voltage drop and that is why lights dim and you have the other symptoms on one or more circuits. An Auto Electric Specialist will go over the vehicles electrical system, circuit by circuit, to find the high resistance or unwanted "load" as it is also termed and repair it. YourMechanic will be happy to have a specialist diagnose this electrical issue and resolve this for you.

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