I have a problem with my 95 Trans Am and cant seem to figure it out? I start the car and reads 13 volts as it runs for a few minutes it slowly goes down to the yellow mark and stays there (11.4 volts from scanmaster) I do have a msd and stereo system, but stereo is off.. Tried 2 different alternators that tested good and does it on both of them.. Stock pulleys too.. Volt meter said 12 volts at the back of the alternator and battery.. Any help?

 

You said you tried a couple alternators, have you tried a different battery?

 

actually its a new battery also, forgot to mention that..

 

First you have to be sure the connections at each device or mounting point are clean. Take them off, shine them up with sandpaper or a wire brush.

Battery connections
Positive and negative cluster on passenger fender
Alternator mounting points
ground strap from frame to engine

Once that is done, check the voltage across the battery before you crank the engine. Should be about 12.6 or a little higher.

Crank the engine over and be sure it doesn't drop below 11 volts while cranking.

After it starts and runs, the battery voltage should now measure at least 14 volts. All these voltages must be done with a hand held meter.

If any of those measurements don't match, let us know. We'll tell you what to do at that point.

 

cleaned up connections and still does it, 13 volts when I start it and slowly goes down to 11.4 and stays there.. Doesnt matter if I have nothing on or everything on.. Im lost..

 

My car has been doing that for a long time now, even with a new alt and batt, but I haven't had any problems related to it. Good luck with it, keep us posted.

 

I dont know what else to check, anyone got some ideas?

 

does your stereo system run a cable to the back for amps(amplifiers)? If so they could be draining the battery even if the stereo is off.

 

yes, I have a 4 gauge power wire that runs to my amp in the rear.. I'll try to disconnect the power wire and see what happens.. But I dont think this is a problem..

 

I wouldn't think so either but you never know!

 

How long has this been going on and has it given you any problems?

 

been going on for about 4 months and no problems, just the thought of my msd and everything else is ran off 12v's and the guage always on the yellow mark just makes it feel unreliable..

 

Assuming your battery is good, the wiring is good and the alternator is good. The only other explanation is a load placed on the charging system.

But you have not convinced me your alternator is any good. Remember the cheap auto parts places can't test your alternator while it's hot.

However, if you feel confident in the alternator. Pull all EXTRA loads like an amp or any other add ons, off the 12 volt system.

If that doesn't bring it back up, start pulling fuses one at a time until it does come back up.

 

my car does this also. however, I have the **** underdriven out of it. The car will be fine while the engine is cool, but once it heats up (especially at night with the headlights on) I'll be at a red light at idle and watch myself drop into the 11 volt range.

I've upgraded all of the electrical contacts with 4awg wire. Next step, I'm going to drop in an Optima Yellow Top and install a high amperage alternator.

I plan to install a pretty high-powered audio system.. i'm going to put a huge capacitor in front of it just so there won't be any sudden voltage drops.