Electric problem at 74mph+. WTF?

[whiteMaro]

I'm having a problem with my 98 A4 that I don't even know where to begin. When my car hits 74MPH or above my voltage drops and spikes rapidly. My interior and exterior lights dim and flash. This happens with or without the headlights on. I first thought this might be an engine RPM issue relating to the alternator so i dropped it into 3rd and brought it up to 73mph with no issue. As soon as I got above 74mph in 3rd the voltage went crazy again. The problem does not occur while the car is in neutral at any speed.

I have no idea how to troubleshoot this problem because I can't duplicate it in the driveway. Its got to be something with the transmission but I have no clue what. Any help would be awesome. Thanks

[cam98aro]

Re: Electric problem at 74mph+. WTF?

i saw this same exact problem on ls1tech, and the problem was either the alternator, or the voltage regulator.. cant really remember which it was

dude even took a video as his dash would go wacko, the gauges would start going to random numbers, etc... i can see if i can find the thread.. but the search there sucks

[cam98aro]

Re: Electric problem at 74mph+. WTF?

ok, i did a quick search, and a bunch of people have similar problems

here is what was wrong:

- low battery
- loose negative terminal
- bad grounds
- bad alternator

so i would say that you should try to clean the terminals, and see if it still does it.. if not, find the grounds, and clean them up.. depending on how old your battery is, get it load tested, or replace it (although the load testers ALWAYS fail a battery.. just a warning), and get your alternator checked out at advance/autozone

[whiteMaro]

Re: Electric problem at 74mph+. WTF?

i saw this same exact problem on ls1tech, and the problem was either the alternator, or the voltage regulator.. cant really remember which it was

dude even took a video as his dash would go wacko, the gauges would start going to random numbers, etc... i can see if i can find the thread.. but the search there sucks

Thanks man ,that would be great. My gauge numbers stay the same except for the volts which dives into the red (1/4 range) and jumps up to about 15. The other strange thing is my trip od resets the next time I start the car after I go over 75. PITA when I'm on a business trip and trying to track my miles.

[whiteMaro]

Re: Electric problem at 74mph+. WTF?

ok, i did a quick search, and a bunch of people have similar problems

here is what was wrong:

- low battery
- loose negative terminal
- bad grounds
- bad alternator

so i would say that you should try to clean the terminals, and see if it still does it.. if not, find the grounds, and clean them up.. depending on how old your battery is, get it load tested, or replace it (although the load testers ALWAYS fail a battery.. just a warning), and get your alternator checked out at advance/autozone

Wow that was quick!

I'll check and clean everything first thing this weekend. The battery is a few years old as is the alt which died 2 days after I replace the battery:rant:. I think I might just replace them both when I get paid on Friday. Thanks for the help.

[cam98aro]

Re: Electric problem at 74mph+. WTF?

Wow that was quick!

I'll check and clean everything first thing this weekend. The battery is a few years old as is the alt which died 2 days after I replace the battery:rant:. I think I might just replace them both when I get paid on Friday. Thanks for the help.

yeah, i think it has more to do with the load put on the engine in 4th gear, lower rpms+faster driving+more wind resistance=higher load put on charging system, which is where you will start to see problems.. although i do think it is weird that it doesnt happen until you reach exactly 74mph

i would get everything checked first before you spend any money, i would kinda feel bad for you to go out and spend $200 on a new battery/alt and still have the problem

[whiteMaro]

Re: Electric problem at 74mph+. WTF?

I don't trust my local shops. Every time I take a battery or alt in they tell me its dead. I can test my own batteries now but I'll just have to take the alt in and hope the guy is honest. I guess I could take it to a few places and average them out:naughty:

[Fondle]

Re: Electric problem at 74mph+. WTF?

autozone can test alternators

[Blizzard242]

Re: Electric problem at 74mph+. WTF?

autozone can test alternators

Yeah if the person testing them knows what their doing.