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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:

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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?

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

Ed

Reply to
Ed
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I looked at the URL graph for battery voltage, and this kind of fluctuation is very NORMAL. The voltage regulator isn't designed to output a signal more stable that what you see on the graph.

In fact, that's about as good as it gets, on a SCANNER. +Real+ voltage needs to be monitored at the battery with a DVM. It will be higher...from about 13.8 to 14.2

Lg

Reply to
Lawrence Glickman

Ed should also measure the AC ripple at the alternator. Volt meter set to AC volts, red lead on the alternator output stud, black lead on battery negative. Anything over 100mv AC indicates a problem.

Reply to
aarcuda69062

aarcuda, is that reference voltage specific for GM alternator, or does it apply to other brand alternators [e.g. Ford, Chrysler?]

Reply to
Knifeblade_03

if you expect / want a steady read, then you might switch to dc - and forget all the little factors involving ac current.

mho v=83e

Reply to
fiveiron

Sorry, I don't follow. If you are referring to the JPG file, it is from a OBD-II scanner. No AC option.

Ed

mho vfe

Reply to
Ed

Fits all brands.

Reply to
aarcuda69062

Why would anyone want to skip an important diagnostic step?

Do you have the slightest idea how electricity is generated in an alternator? (left you a clue there)

Reply to
aarcuda69062

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