voltage slowly drops after driving

[boost97gst]

Figured id go on a post spree . So when i start up i get 13.8VDC. after it gets warm and 20 minutes later its slowly drops to 13-13.2 at cruise.
Heres my thoughts: I just ordered an o2 housing heat shield as i dont have one now. Im guessing, i know a thing or 2 about electronics, that as the o2 housing heats the alternator and wires in and out of it, resistance is increasing causing more of a voltage drop. It DOES look kind of cooked too.
Do yall think the heat shield will help? I mean it cant hurt. If not perhaps i should run new alternator wires. Ive measured at battery(in trunk), junction up front, and off the alternator, they dont vary more than a tenth of a volt.

Im a clinical engineer and have seen how heat can destroy components.

 

[serrilion]

Also need to remeber that your Voltage will naturly drop from when your car is off because your not running your ECU, Stero, Lights, all the connectors in the car... everything draws some power... more so when the car is on then vs off when they r not needed or powered by the turning of the ingnition... just some food for thought there as well

 

[Calan]

Also need to remeber that your Voltage will naturly drop from when your car is off because your not running your ECU, Stero, Lights, all the connectors in the car... everything draws some power... more so when the car is on then vs off

You should always see higher voltage when the car is running (with the same loads), due to the alternator supplying around 14v to charge the battery.

*****

OP - The heat could have cooked the voltage regulator in the alternator. Take it to a parts store and have it tested (several times).

And yes...it's always best to run the heat shields if possible. They make a big difference in under-hood temps.