Electrial Question

[christopher]

I have a 1982 Chevy K-20 4WD with dual batteries.
When you put a test guage on each terminal on one on the batteries there is no voltage. However turn on the ingition and 12+volts.
The truck runs fine and the batteries stay charged but what type of circut can cause this. I normally expect the negitive terminal to be ground, is this the case here.

[VileZambonie]

What do you mean a test gauge? If you put a meter across the B+ and B- terminals it should read approx 12.6 volts. If you read zero at one battery and 12.6 at the other than the battery is open and is useless.

[DnStClr]

Is your truck diesel? One of the batteries is used to start and the other is used to help supply 12v for accessories like a winch or trailering duties. Seperately tho, you should get over 12v when ya put a meter across the battery terminals.  The negative terminal is grounded.

[christopher]

If you put a test light on the B- and B+ of one Battery the the light does not come on until you turn on the ignition.

You guys cleared it up for me.

The reason why is that the two batteries act as one. They are connected in parallel. So for the test light to work with the ignition off.
I would have to hook up the test light on the B+ of one battery and the B- of the second battery.

Thanks

[choptop]

If you put a test light on the B- and B+ of one Battery the the light does not come on until you turn on the ignition.

You guys cleared it up for me.

The reason why is that the two batteries act as one. They are connected in parallel. So for the test light to work with the ignition off.
I would have to hook up the test light on the B+ of one battery and the B- of the second battery.

Thanks

no, you should have the light come on when you put the test meter across the negative and positive post of either battery, and either battery positive to chassis ground should be turning the light on as well. Almost sounds like a ground problem. Recheck all of you connections if the light doesnt come on like I described. B+to B- on each batt and B+ to ground from each bat. The key shouldnt have to be on.

[VileZambonie]

If you go directly across the battery B+ and B- and there is no voltage then the battery is dead or open Regardless of ignition switch position. For 12 volt dual battery set up yes they would be in parallel and all that does is gives you more available amperage and reserve capacity.