NOTSTK

A few weird electrical gremlins are popping up on my 98 12v 5spd.
When idleing sometimes it seems like my alternator stops charging, my lights will dim and my egt sometimes flickers, also I noticed that sometimes while driving below 60 kph my speedo will jump, to like 120 etc.. I looked at the grounds on the batterys and the alternator they seem fine, 2 new 1200 cca batterys, and there is a buzzing in my stereo sometimes.. To me this looks like a bad ground, but where ? When it seems like it stops charging my volt meter will drop a little, to below 13 volts. Is this the beginning of the end for my alternator ? Thanks alot..

Haulin_in_Dixie

Try and catch it when the stereo is buzzing. Put an AC volt meter on it and see if you have some AC coming through. If so you have a bad diode in the alternator. Thats what it sounds like, a leaky diode.

NOTSTK

Would the leaky diode cause the voltage to drop ? It drops sometimes even when the stereo doesn't make the noise.. What about the speedo and the EGT ? Would the leaky diode cause that as well ? Thanks

Haulin_in_Dixie

AC in the system is unpredictable and will cause all sorts of problems. And yes the voltage will drop.

scuzman00

What Hauling says holds a lot of water, but have you checked the chassis and engine block grounding wire connections?? a bad ground connection can wreak havock on charging systems and normal operations of electrical systems. Look for corrosion at the terminations of the wires. Also you need to check wires for internal corrosion beyond the terminal connections. Again, Hauling is an expert at all things CTD from the experience he has tearing apart and putting back together his truck.......

Good Luck in your troubleshooting!!!!

Gary

Haulin_in_Dixie

Something else to check on the ground thing is the small ground strap to the PCM on the passenger side firewall. That controls the charging and the smart dash. It should have a small ground strap from the PCM to the body of the truck. Make sure those screws are tight.

Scuzman, come on, that's gettin deep.....

jaconst

what about the grid fuel heater, would that cause any probs?