I just built a 24v here at work, got it all put bak in, and the truck started right up.

now for the problem

the alt wont charge, and if you rev the motor to 1500 or above, the gauge drops to 8. check the batterys, and it shows its 12v. turn the key off, and right back on, the gauge goes back to working. the abs and the airbag light is also on. ive looked every where under the hood, can find no loose wires. no borken wires, if done a self test on gauge cluster, changed gauge clusters, tried a different PCM. checked all fuses, checked all fuses, and checked all fuses again. i need to get this figured out asap

but other than that, the truck sounds perfect

 

Denso alternator? External regulated? Check the brushes, could be conincidently worn out? Return or ground problem?
Did you check the charging voltage with an accurate DMM? You must have above 13.8V

 

sounds like a bad ground to me.

good luck

 

voltage at the battery was 12.4 so i know it aint charging like its suppose to. all the grounds are clean, and fresh metal where it connects to the block.

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Clean the pcm external ground and clean the battery terminals. It will fix it 90% of the time

 

i cleaned the pcm external ground with a scotch wheel, termanals are good and clean, the mounting service for the ground on the block is bare metal and cleaned.

 

What is the voltage directly measured at the alternator?
12.4? Thats a 60% charged battery. Be careful- recharge external!