can not find short on 1999 se

[thomjohn]

I took my dash out of my 1999 Bonneville SE (3800 not supercharged) to install a new
heater core. Noticed when putting back together the cigarette lighter wires looked like they
had gotten too hot. Disconnected them to check later for another future project as I use
the lighter plug for computer/and or gps devise.

When I got the dash and all wiring reconnected-no ignition (no lights nothing-battery fully charged) and I did the test light trick Took out every fuse, drivers side, passenger side, under the hood- firewall big 40 and 60 fuses, took out those metal fuse plugs too.
The light never went out.

Took my dash out again and found that the orange wire and black wire to the lighter had welded
themselves together higher up in the dash. Traced the orange wire to the fuse box drivers side under
dash and it was not blown. The black wire was traced to adjoining 5 wires in the wiring harness and they
were all ok. No wires going back to lighter-totally removed now.

What do I do to find the short know. Did this blow something someplace else, because the fuse for the
ligther is still good.

[Bugsi]

I'm concerned that your lighter hot and ground wiring were able to weld themselves together without blowing the lighter circuit fuse. I think your 99SE wiring is likly to be identical to my 97SE wiring. The lighter circuit fuse is fuse 9B in the instrument panel fuse block, and it should be a 15 amp fuse. Check to make sure it's the correct value fuse. That circuit in the instrument panel fuse block is powered through 60 amp fuse A3 in the Lefthand maxifuse block. Check that fuse too. Also check 60 amp fuse A7 in the Lefthand maxifuse block, and 60 amp fuse A2 in the Righthand maxifuse block, as those cover the ignition circuits.

You've already located your short circuit at the lighter wiring, now you're looking for an open circuit caused by the short, and that would normally be in a fuse or a fusible link. I think we have the maxifuses instead of fusible links in our cars' electrical designs.

[thomjohn]

All of the big fuses are ok-checked every fuse from small to the large ones in the engine compartment.
With the dash out I stripped all back electrical tape and rewrapped the harnesses. Did not find any exposed
or fused wires except the orange and the black that went to the lighter.

[willwren]

Please clarify exactly what does or doesn't work with regards to lighting, ignition, radio, healights, etc.

[Bugsi]

Yes, something's not right in the description here. It is difficult to believe you have +12V at the fuse box, with good fuses, and no power to anything. If you have +12V at the fuse box and good fuses, you must have SOME circuits that are working. Give us more details. About the fuse for the lighter circuit, I asked you to confirm that the fuse at that location [9B] is a 15 amp fuse. Please get us an answer.

[thomjohn]

the fuse to the lighter is supposed to be a 15 but there is a 20 in the 9B slot-from what I have heard that the
20 that somebody put in there should have blown before the wires fried themselves together.

when the dash was all reconnected (from the replacement of the heater core) is when I found:
no headlights
no interior lights
no turn over from the key
no radio
no fan
no brakes lights just dead like a battery was not even connected
the dash is out again so the short is on both sides of firewall (inside ENGINE COMPARTMENT & immediately
on the interior side where the dash was previously connected.

[Bugsi]

the fuse to the lighter is supposed to be a 15 but there is a 20 in the 9B slot-from what I have heard that the
20 that somebody put in there should have blown before the wires fried themselves together.

I don't feel comfortable going with what you heard from somebody. Let's get it back the way General Motors intended for that circuit to be protected, and put the proper sized fuse in there. Even if you aren't using the lighter circuit right now, it could be that having a 20 amp fuse in there allowed your lighter's wires to become damaged from their short, where the 15 might have blown. While I agree that a dead short should have blown a 20 amp fuse just as easily as it should blow a 15 amp, I can't advocate changing the protection circuit and then trying to justify scratching my head and wondering why the wires melted.

Do you have +12 volts at the fuses at the fuse block? Tracing electrical power is pretty simple, just stick a meter from a pin of the fuse to ground and see if you have voltage, then move further down the circuit. Check at the maxifuse locations I specified earlier, and report back with a yes/no as to whether you have +12 volts there. If you do, move on to the instrument panel fuse block and tell us if you have +12 volts there.

the dash is out again so the short is on both sides of firewall (inside ENGINE COMPARTMENT & immediately
on the interior side where the dash was previously connected.

If you have a short, you'll have smoke, fire, melting wires, or blowing fuses. As previously explained, at this point you almost certainly have an open, not a short. Voltage test the locations I specified and get back to us whether you have +12 volts at those locations or not.

[thomjohn]

will get back to you guys this weekend-got early flight to NYC and get back from
work Saturday afternoon. Thanks for the help and ideas so far.

[thomjohn1999]

Had a broken cable on rt side of the big fuses, top of firewall-rewired and all is fine.
Wired direct to the battery with inline 15 fuse for a new outlet for the GPS or future
computer use. Changed out all hoses-new heater core-new overflow tank-new water
pump-just made work trip last week to Nashville. Total miles round trip was a little over
1,000. Ran great and had more heat coming out than ever.
Guys-thanks a bunch for all your help and diagrams to look at-could not have done
all of the above without this site.