Electrical Surge/Drop
 

I've got a 94 mustang GT and I'm having trouble with the electrical system. It seems that there is a somewhat frequent surge or drop in voltage. It's happened on a few occasions, and I'm not sure what to link it to. The battery and alternator/regulator have been replaced, so I've pretty much ruled those out. Connections appear to be good and clean. What happens is on occasion the Electrical system seems to "reboot" (for lack of better explanation). the voltmeter needle drops and appears to be powered off for about 1 second, and then returns to normal. I've also noticed that the needle is a bit "jumpy". If the radio is on, it sends a fairly loud pop over the speakers, I'm assuming this would be the amplifiers for the Mach 460 sound system powering off and on. I can't seem to find anything to relate it to, it doesn't seem to be dependant on anything like the fan coming on or off, etc... Possibly a relay switch? Any ideas would be greatly appreciated, as this is driving me crazy.

Thanks

I do not have any answers but I have been having similiar problems with my 90GT. All my problems started when I installed a new stereo. But, I ripped that out the next morning on my way to work when I realized that I must have screwed up, due to the "electical burn" smell. Like you I have a brand new alt and battery now and that does not seem to be the problem. Anyway I will be sure to let you know any info that I find out.

[This message has been edited by JM90GT (edited 08-29-2001).]

It is your alternator. It appears that the voltage regulator slip rings were improperly installed on a bunch of the 3g alternators. The slip rings are what the carbon brushes ride against on the rotor. What happens is the carbon dust from the brushes builds up and creates an electrical path to ground across the the melamine insulating material. This can result in a High or Low voltage condition and usually occurs when the vehicle(engine) is under load.

The fix is rather easy. Remove the alternator. Remove the voltage regulator. Mark the case for alignment/clock position. Remove 3 long/small diameter bolts holding case together. Look at the slip rings(one assembly). They are probably touching some of that gooey crap. Use a tool to seperate the slip ring from this stuff. Sliding the slip ring down the shaft a little is allowed just observe where the brushes were wearing and don't go to far. Next dip the rotor in a bucket of water to rinse off the carbon. Repeat this several times. Let rotor dry/blow dry and reassemble. Use a paper clip or similar device to pin the brushes back up in the regulator for reassembly.

Why this has not made a recall yet baffles me. Does anyone know of a TSB on this? The alternator on my 90 came from a 95 and was spiking high. The auto electric shops I took it to said "It tests ok!" but the rotor windings were grounded. Amazing, none of them even tested it to see if it was grounded.

Oh yeah, this problem doesn't get fixed in a typical rebuild. The slip ring must be moved to fix this problem. I received a 3g rebuild for a customer and it was screwed up the same way.


Mike

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[This message has been edited by moosejaw (edited 08-29-2001).]