Volt Gauge Question - 02 190 Versatile

[Kurt Franz]

Need to know if the battery isolater could be causing my volt gauge to consistently register on the low side on my 02 190. I know on the 05 and later models the gauge fluctuated due to the electrical load at the time. This is not the case on an 02. This is my first Chevy Express, but I would think that normal would be at or close to 12:00 on the gauge. I can see it dropping a bit with a heavy load on the system. It currently reads about 11:00 on the gauge all of the time.

The alternator is brand new - was replaced because of the above described issue - no change.

The battery is 6 months old and tests 12.6 across the terminals.

KF

[SteveJ]

Verify the voltage with a meter with the engine running.

[joeski]

Should be around 13.8 volts or higher with the engine running. Harbor freight has cheap volt meters.

[KurtFranz]

Thanks - I appreciate the responses, however what I am wanting to know is if the isolater could cause this issue as my volts are lower than the 13 plus that it should be. My apologies if I was unclear in my original question. The battery is good at resting voltage - it is basically new as is the alternator. Trying to figure out from there if it could be the isolater. I will have to figure out how to test that.. Was thinking that if there is a problem there it could be that the gauge is reading low because it is charging two batteries instead of one. I am now answering my own question it appears ....guess the next thing to do is to take the house battery out of the loop and see what happens.

No need to respond to this unless I am missing something in my logic ....

Thanks

[booster]

The isolator is going to drop the voltage by about .7 volts and the gauge is likely on the battery side so is seeing the lower voltage. If the alternator is set at 13.8v which in the era of 2002 is certainly possible, especially if it has been replaced before, you would see low 13s for voltage at the battery.


With the voltage dropping over time, It think I would start looking for corroded or loose connections in the positive and negative cables, including the body to engine connection on the passenger side fender to the engine block.


Of course, you should confirm that the gauge in the van is reading correctly as they can be very inaccurate. A Harbor Freight cheap multimeter should be good enough for that.

[markopolo]

I think that a 2002 Chevy Express will have a voltage sense wire from the alternator. That smaller gauge wire connects to one of the outer posts on the isolator, not the center post. With the OEM alternator, voltage at the outer posts should be 14.4V or even higher if the alternator is cold. When hot, it might drop to 13.8V or so. The isolator center post will be about 0.7V higher than the outer posts. The OEM alternator tries to maintain 14.4V based on the input from the voltage sense wire. It compensates for the 0.7V drop caused by the diode type isolator because the voltage sense wire shows the 0.7V drop.

That's how it is on my '97. That series of van spans 1997 to 2002.

The alternator is likely a CS144. The isolator should be a 4 post type and have 5 wires connected to it.

There are a couple of files attached to this post -> https://www.classbforum.com/forums/f...tml#post129804 <- that should help with isolator troubleshooting.

[Kurt Franz]

Thanks to all who have responded to this!
Great bunch of folks here for sure