Redwoodmike

I have a 2000 1500 5.3. I had voltage fluctuations so replaced the alternator battery and serpentine belt. It seems to fluctuate more now. The engine is grounded as well as the ground strap from the firewall that leads behind the engine. Is it possible I bought an defective alternator or battery directly off the shelf?

chem_man

First make sure that the battery terminals on the end of the battery cables are clean. Then, make sure that the battery cable terminal to battery connections are tight, but not cranked down, I believe the torque specification is something like 11 ft-lbs. I would also check to make sure that both the negative and positive battery cables have not been infected with the green grunge of battery cable destruction. Also check the cable that comes off the alternator and goes to the battery jumping convenience box is tight at both ends and has not been infected by the green grunge as well.

You do not mention anything about the small (relatively speaking) ground cable that goes from the negative battery cable (battery end) to the body/frame ground. It needs to be clean and tight as well.

If all that checks out, you could have purchased a battery/alternator that were defective from the factory. In that case have them tested by a parts store to see if they are good or not.

Good Luck!

Redwoodmike

so I checked. No green stuff.. i probed a test light into the small wire off the negative. Its grounded. Everything seems good. I noticed a small belt squeak when I come to a stop not even 2 seconds long. Could this problem stem from a bad tensioner? The belt seems and the tensioner seems to retract when I pull on it. Not sure how tight it teally needs to be. Its not loose. The belt will twist with 2 fingers about 30 degrees. Thanks

kevinkpk

I don't read where you replaced the tensioner, I replace the belt, and tensioner as a pair.

Redwoodmike

Going to replace the tensioner to see if thats the problem

Redwoodmike

Tensioner didn't help. Took it to the local parts store everything tested good. Would the small compressor belt cause any issues. Looks like it could use changed

kevinkpk

I have to think you are refering to the AC belt? No. How are you monitoring the battery voltage?

Redwoodmike

Just the battery gauge on dash. When I come to stop. Red light. Stops sign. It dips down to about 10. While driving stays above 14. Only when slow or stopped. Lights dim. Engine idles about 500rpm. In park or drive

kevinkpk

I believe your problem might be the low idle rpm, it should be about 750 rpm at idle.

chem_man

I hate to say it, but checking for/verifying ground in the battery charging circuit using a test light is meaningless because you cannot quantify the brightness of the light. You need to use a digital multimeter (DMM) and measure either resistance from point A to point B of a wire disconnected from an end, or voltage drop across the wire. You could still have a bad battery cable, wire or connection someplace.

Ideally, you should be able to remove the battery to starter cable and measure it's resistance to make sure it's OK (essentially zero ohms), or measure the voltage at these points with respect to ground - Battery Terminal, Quick Connection Block, Stater. The voltage should be the same or within a couple of tenth of a volt at each point. If the voltages are not within say 0.2 VDC of one another, then you have a bad battery cable. A test light will not tell you if have a 0.1 VDC or a 0.6 VDC voltage drop in a circuit because it will be essentially the same brightness for both values.

Now, the other thing to remember is that your alternator is controlled by the PCM so when your battery's voltage is high enough, the load on the electrical system is relatively low, and you are coming to a stop at a light or a stop sign, it's normal for the PCM to tell the alternator to "stop charging" in order to reduce engine load and increase gas mileage. Also, the voltage gauge on the instrument panel is a relative indicator and not a precision instrument.

Considering you have a 20 year old vehicle, I would just go ahead and clean up any and all ground connections I could find in the engine compartment, and then also clean the connections along the positive battery cable all the way down to the starter. I would also inspect the insulation all along the battery cables, and check the resistance of each cable while flexing it to make sure that the cables are still mechanically and electrically tight. I have a 1999 Silverado, which is not that different than your 2000 Silverado, and while I am not having any starting problems or strange voltage readings, I am seriously contemplating replacing my battery cables come spring weather.

Good Luck!