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Changed engine ground wire, no power. 02 DTS

4213 Views 20 Replies 6 Participants Last post by  Submariner409
So I had some issues with my dash doing crazy things, things turning off while driving. Discovered that in addition to a new battery, I needed a new engine ground wire. Replaced those both, now I have no power to the dash/ignition. Bolts to the ground wire are both tight and so is the battery. To test I had ground, I used a jumper pack from pos jump point on the front fuse box to the strut bolt, where I've always jumped from. With the broken ground wire, it would not work at all unless I hooked ground to the engine directly. Now it has strong connection and sparks when jumping, but the ignition has no power without the jumper. When the wire was broken, the dash would at least come on and read some voltage. The only thing different between that and this is I have the radiator fans both unhooked so I can make sure everything is good before I put everything back together. Anyone have any idea why the power is not going from the rear battery area to the front?
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A "12 Volt" automotive lead-acid battery should show 12.6 Volts, fully charged and disconnected from anything for a half hour.

That same battery, in the car, should show 12.4 - 12.6 at Key: ON and will allow a system charging voltage of 14 - 15.2 Volts, depending on battery condition. If, after startup, system voltage goes to 14.8 - 15.2 it will stay there for some length of time then, as the battery comes back up to full charge, ramp down to 14.2 to 14.6 Volts and stay there. Amperage, which you cannot see, will vary as the state of the electrical loads changes.

After 2005/2006 the charging specifications are much more dynamic so the DIC will show a much greater voltage spread when driving.

Negative terminal to frame is ground to ground - no voltage will result. Red = positive = +, so + to ground will show system (not necessarily battery) voltage - set to Volts DC.

When all else fails, read the directions ..........
Not for his 2002 DTS - 13.8+ to about 15.2. His (DTS) car came with the 140 Amp alternator.

Over 15.5 or so he'll see a system voltage high message.

Mine floats between 14.4 - 14.6 all day and night, rural or Interstate. Exide Group 79 lead-acid battery.
Automobile charging systems take into account the average sensed internal battery resistance: a dead battery looks like a short to ground - little or no internal resistance. A fully charged battery has a high internal resistance - that fully charged value can vary depending on battery construction.

That resistance value will vary the charging rate for both voltage and amperage.

What is the running system voltage after 50 - 75 miles on the Interstate ? BatteryMinder notwithstanding.......... My STS sits in the garage with a BatteryMinder connected at all times - 13.2 Volts - and when we disconnect, start up, and head for a 120 mile round trip lunch the DIC voltage is 14.4 - 14.6 each time.

EDIT: DO NOT, ever, use an old ferroresonant "trickle charger" on a battery. The new "smart" chargers are just perfect - but an old ferroresonant hummer will kill a battery in short order if it is left attached and turned on.
System voltage will stay in the 14s with your 2002 - any time the engine is running at greater than loaded idle speeds.

Voltage - in the pre-2005 or so systems - is always held a tad high with varying amperage keeping a full battery charge.

Drive the car for a while - one of your "long" drives. Voltage indicated at 14.x ? Park, turn off the engine, have a drink - come back and turn the key: ON (no start) - what's the indicated voltage - 12.6/12.8 ? Good to go. Start the engine - voltage goes right back to 14.x, doesn't it ?
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