1. Home
  2. General Motors Forum
  3. Abnormal alternator output fluctuations?

Abnormal alternator output fluctuations?

I'm now thinking there may be a more pervasive electrical problem causing the Herky Jerky symptoms (chuggle). The system voltage always shows up kind of ragged in the scans. Take a look at this:

formatting link
Here are my notes on the episode shown there:

+++++++++++++++ 4.18: 12.4 minutes into trip. CC set at 66 mph, maintaining 67, TCC on. Then speed (or at least the speed sensor?) suddenly drops to 61. Throttle opens (as it should this time!) but seems happy to hold 61 mph for 8-9 seconds, why? TCC stays on. Battery voltage looks rough throughout, between 13.4-13.6. There were a few dives in inj. pulse width before and after the speed fall off.

suspicions: Since events seem to be preceded by drop in road speed, could it be a sudden increase in drive-train resistance? Or, ref voltage effects on speed sensor?

-----------------

Does anyone know if this kind of fluctuation is normal on one of these GM CS-130 alternators?

Ed

Reply to
Ed
Loading thread data ...

@#@

That GM alternator should run at 14.-14.2v depending on system demand, the volt regulator tries to keep it in the above range. Bad batteries shorts and opens loose connections burnt rectifier bridge bad windings could all create problems.

Ray

Reply to
Raynaud

Thanks, Ray. So, given that this one is bouncing around between 13.4 and 13.6V would you replace it? After checking all the obvious connections, of course.

Have you observed scans like this for a good alternator? Do they always show the fluctuations?

Ed

Reply to
Ed

@#@

You will see slight fluctuations due to rectification by the diodes , if one or two are open or shorted you will see an sign wave type scan because it is part alternating voltage.

Ray

Reply to
Raynaud

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.