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Sunday, March 06, 2016

Car alternator problem at high RPM

On the new little car, I had noticed an issue while driving, but it didn't give me much concern... until Friday morning.

What I had noticed was that the lights would noticeably dim as the engine revved higher, typically just before the car up-shifted.  It was not affecting the electrical system or my ability to start the car however, so I ignored it.

On my trip to work on Friday though, it became impossible to ignore any longer.  After several minutes on the highway, the dash lights rapidly dimmed to the point where the gauges were not readable, the stereo skipped a few songs, then quit altogether, and the engine began misfiring.  Clearly I had a big problem in the electrical system - as in major loss of voltage.  The previous owner had replaced the battery just before selling the car to me, so I was certain that the battery was not the issue.

As the engine sputtered its last, I pushed the shift lever from drive into neutral, so that I could coast to the side of the road.  To my great surprise, as soon as I took my foot off the gas and let the engine drop back down to an idle, the lights brightened, the engine sprang back to a normal idle, and the stereo started blasting again.  Voltage had recovered.

As I continued to coast, I revved the engine hard, and the lights dimmed again.  Below a certain engine speed, the alternator worked well, and above that speed it seemed to be either not working or causing a partial short circuit.  Like most modern cars, this one does not have an ammeter to tell you if the system is charging or discharging.  In fact, this car doesn't even have a voltmeter.  I guess that's what dim headlights are for - to let you know the voltage isn't normal.

I made it to work by going a bit slower than normal.  This allowed the alternator to run at a lower speed than the threshold where it failed.  At work I did a brief internet search, and found several instances where other drivers had the same issue - although on different car models.

I replaced the alternator and both the drive belts, as they had minor cracking.  It took well under an hour.  The alternator is the shiny object at the center.

Since then, no issues with the lights dimming.  I haven't checked the electrical system with a hand-held ammeter, but it's pretty clear that the problem has been resolved.

On another note, there is a minor leak on the power steering pump.  I noticed the leak during the above repair, and found the reservoir to be quite low - empty in fact.  I looked up the cost of a rebuilt replacement pump from the local parts store, and it was $125.  The rebuild kit is $18.  I think this will be a rebuild.  Perhaps a post about that will be next.  I really need to get back to dam failures... those are epic events!

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