I am having an issue that I cannot figure out with my 05 evo 8.

At idle my car sits at 14.5 volts, when I rev up the engine, the voltage drops below 12v (11-11.5) I had the battery tested, it's good. ( 1 year old red top optima) and the alternator checked out good too (also 1 year old)

Anyone know what could cause this problem?

 

What is the problem you have having exactly? Does the car die? Does it need a jump from time to time? I'm not sure of your original problem other than the voltage issue.

 

Low voltage problem which causes two check engine lights to come on ( brake light, can't remember the other ) my car ran at 14.5v at all times previously.

 

Two warning lights come on? Brake and what else? I doubt you have 2 check engine lights. Is your check engine light on at all? Check your belt condition, make sure all your connections on your battery and alternator are tight! You should not be able to move them at all. You may have a bad ground somewhere also. Make sure grounds are clean and tight. If everything checks out good, you may want to bring your battery and alternator to another shop to have them tested. I don't care if they're a year old. I've seen bad parts many times right out of the box. Nothing lasts forever.

 

Sorry, I meant dummy lights are on not the CEL. (Brake and battery) I had the alternator checked again, it works great. Battery is also good.

All connections are good, zero corrosion, nothing is loose. All belts are in great condition about a year old, no cracking. All pulleys on accessory belt spin free. Tensioner was tight, seemed to operate correctly.

I am at a loss here, this makes no sense.

 

If all your grounds are clean and tight, you might try changing the alternator and retesting the charging system.

 

Problem found, power wire for alternator corroded badly, but was hard to find under the sheath of the cable. Thanks for the help