I have an 1989 GTA w/ a 5.0L 5spd TPI. When I drive at night the dash lights flicker.. sometimes very little, and sometimes really pronounced. Today, when I was coming back from school, they were going kinda crazy, and I could see the voltmeter gauge moving with the flicker. Also, more importantly the idle gets messed up when it does this it will go up and down about 400 rpms when it flickers. The idle does this during the day too, even when the lights are on.. so i don't think it is cause by the lights being too much for the alternater. I have a amplifier and sub-woofers, but if I turn the stereo off it flickers just the same. I have a new battery and i replaced the alternator a little over a year ago with a 105amp replacement. The flickering and idle is kind off intermittent, and it's intensity changes too. Is there a voltage regulator that isn't part of the alternator? could that be it? Any suggestions.. this is really annoying. It sucks having flickering insturments and a bad idle sometimes on a really nice looking car. Oh.. and I don't have underdrive pulleys. Thanks. 89GTA5spd

It sounds Like maybe a loose Ground Cable. Also Are you Running a Cap before your Amp??
My Dads Astro Had This Problem as well. Your Idle is messing Up from The voltage Drop because your spark is weaker from the coil. Also Make Sure to check your Alternator. I have had to Go through 3 before I got a good one before so just because its new doesnt mean its good. If all of that checks out then Start Checking Fans and fuel pumps and anything elese electrical.

JJ

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*89 TTA 31K miles
*89 TTA Indy Pace car 33 miles (no not a typo)
*89 2.8 liter TTA Replica 106K miles still runs strong
*91 L98 TA convertible 46K miles
*86 TA new to my Family (in restoration)

I'm gonna see if my alternator warranty is still good and take it back if it is still under warranty.

All the straps _look_ good, but is there any way to know for sure.. like testing with a voltmeter. should I take them off and remove corrosion.

I don't have a cap on my amp, but It doesn't matter if my amp is on or off it will do it either way and it's only a small amp (like 300 watts rms).

The idle is real annoying.. it would be soo nice to have a good idle and steady lights..

Is there anyway to test the alternator ON the car? This is my only car and I am at school so I can't use my parent's or brother's car (both ford's anyway ).

89GTA5spd

My car has had electrical problems and the alternator is one part that we put on. A neighbor said that a way to check the alternator while it is on the car is to take a screwdriver and while the car is running. CAREFULLY move the head of the screwdriver toward the center of the thingy (forgive me, I don't know the name) where the belt runs. There should be a magnetic field there. If you don't feel any magnetism, the alternator is bad.
Hope you are successful!