Hello,I have a 94 suburban 6.5td the problem I am having is that when you turn on both blower motors,head lights,radio volt meter goes in to the red say 9-10 volts turn it all off goes back to 14 volts,but if you check voltage at alt and batteries with the blower motors on head lights radio on it is 14 volts when gauge is reading 9-10 volts I have cleaned and check all grounds the batteries have load tested good and alt has tested it is good.I have checked voltage at fuse pantle it is reading whatever the gauge reads thanks for the help

 

So are you running your batteries dead? Not sure what the issue is....

 

No the battries are not going dead, but having low voltage to fuse box gauges jumping around and radio cutting off

 

how is the cable that connects both batteries?
what are you getting when the truck is running high rpms? should be 14.6
my truck used to do the same thing, i ran anouther power cable from battery to battery.
turned out to be fine.

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the gauges in these things arent the best in the world either

 

At high rpm it stays 9-10 volts untill you turn everything off,Ill try the battery cable,where is the main power feed to fues pantle at