i have a 98 gt for starters, when im driving around the city or anywhere for that matter, if i let my rpm's go up to around 2,500 my radio cuts out and my battery guage needle on my dash surges up to the high mark. when i shift and the rpm's drop back to 1,500 or so, my radio comes back on, and the battery guage needle falls back to the normal position!!! (this happens through all the gears) can someone please help me with what is causing this and how to fix it?

 

Since it's rpm related, I would suspect something with the voltage regulator in the alternator.

 

lol...well my headlights surge on and off.....not all the time just sometimes, really fun on backroads at night.

 

That would be the regulator. My 65 did that due to a worn regulator, too. Kinda cool, but didn't want to attract any unnecessary attention with those race mufflers I'm running....

 

wait, the headlights or my radio cut out problem has to do with the regulator?

 

Yup. It's rpm dependant, based on what you said. Many electronics will cut out when facing an over-voltage condition.

 

soo, i should pick up a bigger alternator and shlap that bad boy on my car and problem solved?

 

You only need bigger if you have an upgraded sound system or something else that draws a lot of amps. If you're electrical system is stock, stick with the replacement.

You may luck out and still have a shop around that can just replace the diodes in the VR for a low price...

 

my gt has the mach 460 sound system that came with it. which i would imagine needs more juice to it, when i bought the car i think it had an OEM replaced alternator, maybe he bought the one that goes in a gt with the stock audio system? thanks for the help so far, keep it coming

 

I only see 105 and 110 amp alternators being listed for the GT. Not really any difference between the two and either would be more than enough for the Mach 460.

Since the alternator is a reman, it may have defective/cheap parts that have already failed. Another killer for alternators is a dead battery. Alternators generally aren't designed for that kind of a load, and they will fail when put under that much stress (not always, but they will definitely fail much earlier than normal).