How come my chevy doesn't hold a charge

Hi,

With the engine off and key removed from the ignition, disconnect the negative (-ve) battery cable from the battery and then connect an Ammeter (function found in a DMM- digital multimeter) between the -ve battery cable and the -ve battery terminal i.e. the meter is in series connection with the earth connection to the battery i.e. chassis earth > -ve battery cable > meter lead in - meter lead out > battery terminal.

Set the meter to measure DC Amps 10A scale. The normal current measurement is between 50-75mA (milli Amps). This is the amount that is normally needed to maintain the clock, radio settings, any security systems (if fitted) etc

If you measure more more than this amount, start pulling the fuses one by one and then check when the reading drops to the normal amount.

Knowing which fuse it is will tell you what circuit is draining the battery. The fuse allocation chart either in the fuse box lid or the owner manual tells you what circuits the fuse supplies. Here's a link that also shows what circuits the fuses supply.

Be sure to replace the fuse you have removed, before removing the next one so as to not confuse which fuse belongs where as they may have different ratings.

You need to check both fuse boxes, underhood and passenger compartment if it doesn't show up if only checking the one or the other fuse box first.

Start with the lower rated fuses first i.e. 10A, 15A, 20A as some of the higher rated fuses i.e. 40A, 50A etc, probably feed the lower rated ones. This is so that if there is a fault in a circuit it only blows a minor fuse and not a major one that could affect other circuits which are working normally.