Well, this monitor did the trick, for now all I do is plug it in the cigarette lighter, and voila, I can tell if it's charging. As said, most times it's charging, but now I have the security of knowing if/when it's not, and I don't have to spend over $300 to get a new starter motor but at least the mystery is solved. The monitor also indicates the battery voltage when the motor is not running there's a nice diagram that comes with it that tells you what's good and what's not. If you have a suspicious electrical charging system, I highly recommend it. I have a 9 year old toyota truck that has a questionable system. It charges most of the time, but I never knew when unless I actually got out and put a voltmeter on the battery with the engine running.

Es una unidad compacta pero que realmente brinda la información necesaria, tanto con el vehiculo apagado, como cuando esta en marcha. No más manejo a "ciegas" en aspectos eléctricos, de una forma práctica, portátil ahora puedo conocer el estado de carga de la batería, el funcionamiento del alternador y de la electrónica de control, así como el desempeño del sistema con respecto a los accesorios eléctricos que tenga activados en mi vehiculo. Buena visibilidad de la pantalla, leds de indicación de situación (rojo, amarillo, verde). Lea el instructivo adjunto y disfrute de la información que brinda.

I have a 20 year old Nissan truck that has an "iffy" alternator. It charges most of the time, but I never knew when unless I actually got out and put a voltmeter on the battery with the motor running.

Well, this monitor did the trick, for now all I do is plug it in the cigarette lighter, and voila, I can tell if it's charging. As said, most times it's charging, but now I have the security of knowing if/when it's not, and I don't have to spend over $300 to get a new alternator (at least until this one finally gives up the ghost). The monitor also indicates the battery voltage when the motor is not running (there's a chart that comes with it that tells you what's good and what's not).
If you have a suspicious electrical charging system, I highly recommend it.

This item is very useful to give me a pulse on my camper's marine battery. I bought an alligator clamp dc extender for my battery and then plug the Equus right in for a reading.

I looked at several gadgets of this type, and settled on the Equus because it had the features I wanted and better reviews than other similar devices. I have a 1991 Nissan 300ZX Twin Turbo, and these cars are notorious for having alternator failures. The car has a full set of gauges, but there is no voltage/amperage dial and I wanted to be able to monitor the battery voltage and charging status whenever the car is being driven without running a bunch of new wiring to an added gauge. The 3721 does the job, is well built, and fits in with the other items on the center console perfectly. I'm grateful to report that the charging circuit on my 200,000+ mile Z appears to be working flawlessly, but it is good to be able to keep an eye on it. The only problem I encountered is that I bought two of these items and couldn't get the other one to fit in the lighter socket on my Pathfinder without covering up other things I need to see - the Equus is just a bit bulky, so you have to find a spot where you have a lighter/12 volt power socket and the room for the device. I really like the way the display can be swiveled for different mounting situations and I also like the way it displays voltage, charge status, and has an LED that shows the electrical status at a glance as well. I highly recommend this product! I also highly recommend the 300ZX Twin Turbo, but that is a different review for a different day...