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Truck Repair/2007 freightliner century fault codes


I am getting 2 fault codes: inst volts low 140 168 01, and Low 137s004 01, do you know what these codes mean? I am also noticing a voltmeter problem. at idle my voltmeter is around 14 amps. while driving it drops to 13.25-13.50. could this be a bad alternator?

I tried to google your codes and it doesn't really bring anything up. With key on engine off it should show 12 volts. with engine running should show 14 volts. when you turn your lights on it should dip down for a second then pop back up to 14 volts anything over or under is usually a issue with a alternator regulator which is internal of the alternator. If your wanting to tackle it yourself first thing I would do is get you a battery load tester. undo your battery cables and load test your batteries to make sure none of those are bad and giving you a bad reading. Then with the engine running load test your batteries again. Most load testers have a feature to load test to check if the alternator is putting out the proper volts.
As for your codes call a freightliner dealer I've always had good luck with telling them the code and them telling me what it means without charging you for it.

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Jeff Drumm


I Can answer any question pertaining to semi trucks and trailers. Have no experience in the automotive field so not able to help in that area.


My experiences in Semi Trucks is. I own my own truck and i presntly maintain a 80 truck fleet. Can handle any questions pertaining to a truck have tore apart and rebuilt every aspect on them. Fleet I deal with is Mainly Volvo trucks and a handful of freightliners. Work on automated transmissions on a daily basis along with carrier apu's. With engines my specialty is the 60 series Detroit but do work on the cummins isx the n-14 and the ism. and also the Volvo engines.

Have a College Degree from university of northwestern ohio in diesel and agriculture mechanics. Have 10 years behind the wheel driving a truck and 4 years working on trucks full time. Also have grown up on a farm so have been tinkering on trucks and tractors all my life.

Awards and Honors
I've gone through online schooling and have received certificates from webb wheel, Timken and Volvo academy.

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