intermittent power failure

[tlstevens]

I have a 99 mustang with a 3.8. Sometimes I get a whine through the radio, and it is then that if I turn on the air conditioner, then gauges go crazy and I lose complete electrical power for about 10 seconds or so, then everything comes back on and the motor starts again. I suspect a bad ground but I'm not sure. It doesn't do it unless I turn on the a/c and it gets that sudden surge of power. Anyone have any ideas? The radio whine is intermittent.

 

[cjones]

when you say that you lose all power, you actually mean ALL power. no power at the fuse block, right?? or just no power at the dash and computer.

also, if you unplug the A/C compressor's electrical connector can you duplicate the problem??

check all grounds (engine, chassis and computer), check bat cables, check main fuse block connection.

if ALL power then check voltage between battery positive terminal and engine ground when you duplicate the problem. if you have power then check between fuse block and engine ground.

 

[tlstevens]

I'll check all that tomorrow. Thank You. When I say ALL power, I mean, the engine dies, all lights go out (headlights, dash, interior light, etc...)

 

[Skymarshal]

If you're losing everything, I agree that it sounds like a bad ground. If it were a break between the alternator and fuse block or battery and fuse block, the remaining power source would keep everything going (although you'd have some other electrical problems). Since you're losing everything, one of your grounds is intermittantly open.

I haven't heard of such a problem since my family owned a Sterling 825 back in the '90s. The whole electrical system was made by Lucas- the infamous "Prince of Darkness". That car would do the same thing every so often- everything would die for a few seconds while driving and then come back on! I'm sure it was a ground issue.

 

[tlstevens]

It completely died on me this morning in the middle of traffic. No power to anything, but made an awful buzzing noise under the dash. When I moved the wire from the battery to the fuse block, everything came back on, and I have yet to be able to duplicate the problem. The wire was tight, but did have a small amount of corrosion on it. I cleaned it and reinstalled it. Maybe that was it since I can't make it fail again.

 

[cjones]

hopefully that was the problem. we were looking for a loose/corroded connection.

 

[tlstevens]

I hope so. The wire wasn't loose, but when I pulled around on it, that was when the power came back on. As much as I've tried to replicate the problem, I have not been able to. If that was it, i couldn't have asked for an easier fix.