Q: Battery light on only in summer when a.c. on

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! I have a 1999 mercury mystique. Every summer once it gets hot the battery light will come on and every now and again the car will turn off when I have my AC blowing this only happens in the summertime. I recently bought a brand new battery from Walmart and having the same issues I'm sure once October rolls around the situation will go away but until then what is my problem

High temperatures mean high (or "higher") electrical resistance in the car’s electrical system. As resistance in a wire, terminal, or contact increases, current flow is impeded and voltage drops. This may explain why you are experiencing this problem when ambient temperatures are high but not low. If you request an electrical circuit/component diagnostic the responding certified mechanic will perform the necessary diagnostics to find the circuit with the bad component or connection, if that turns out to be the issue. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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