01 montero sport 4x4 Bat/brake light on when turning on ac.
When turning on ac, battery and brake light comes on then has electrical power surges.
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The warning lights indicate that there is a problem with the alternator output.
With the engine running, use a DMM (Digital MultiMeter - Voltmeter function) to check the voltage appearing across the battery terminals. It should be roughly between 13.8 - 14.3V DC.
If it is not, before you consider replacing the alternator, turn OFF the engine and then check that there is no oil leaking onto the alternator. If it looks like there is or has been, clean and dry off the alternator and the area around it as best as you can and then see if you can see where the leak is coming from. It may be coming from the the valve cover which is known to actually work loose and leak, or if not from there then maybe the cam shaft oil seal on that side of the engine.
Hopefully this is of some help.
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