m37 batteries

[nutsfor59]

hi,how much if any will the condition of the batteries affect the dash voltmeter,on a whim i put a load tester on each of my batteries and each barely made the ok range ,just a hair from the weak range,they are about 3yrs old and have been thru a few winters now in a unheated garage in the m37,they are big heavy batteries for a dodge diesel truck that i purchased new about 3yrs ago,just curious .........

[Joe]

The condition of the batteries should affect the voltmeter on the dash. That's what it's there for. The only difference between it and the voltmeter on your load tester is that the later also puts a significant load on the batteries for faster and more accurate results.

It's common for many types of batteries to show full voltage but not to be able to produce enough current when they're weak. That's why all true battery testers are designed to place a load on the battery while checking the voltage. Even flash light battery testers do this. You can turn on the ignition and lights in your vehicle to place a moderate load on the batteries but that won't necessarily tell you if the battery is good enough to provide cranking current.

Batteries need to be checked for both voltage and current. Hence the use of battery testers and not just simple voltmeters. OTOH the dashboard voltmeter also monitors the charging system when the vehicle is running and can detect other electrical problems as well.

[cuz]

Yes bad and/or tired batteries can affect dash voltmeter readings when the alternator system is operating. To eliminate the batteries as suspect take them out and to a battery shop for testing. It is an expected activity when a technician needs to run a series of tests on any alternator system to first insure the batteries are in good condition and fully charged and that all electrical system connections are clean, corrosion free and tight.