Volts at idle... (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Ghostrider I

I wear many "heads" as I have many vehicles.
Joined
Jul 4, 2017
Threads
147
Messages
1,120
Location
Charlotte NC
I had my alternator rewired to 160 amps recently. Upon cold start (pre glow not needed as it is in the high 80s) the truck starts effortlessly, and the factory voltmeter reads just above 12, with the idiot light on. However, when you depress the throttle, volts go off and all is good. In addition when the lights (6000K LEDs) are turned on the tach bounces a bit. Should I strike up the idle a bit? It idles fairly low, approximately 600 rpms.

Thanks!
 
Keep idle at factory spec (whatever that is) , alternator should keep up.
With higher idle shifting might give more grinding/ unpleasant shifting, depends of wear.

I would not look at the cold start first minutes as reference, just drive a bit and should be fine after a few minutes.
If light is still on then look at other ways to improve output (pulley, adjust voltage, maybe idle if it is below factory spec)
 
Typically on old school alternators/regulators, the 'idiot light' is actually a key part of the system. It provides a current path (so it really needs to be an incandescent bulb...) to initiate the field startup. As the alternator spins up the field generates itself and the field voltage increases so that the +ve value on one side of the 'idiot light' is close to the same voltage as the other side of the bulb (ignition +12V) and the light goes off.

Battery voltage should be near 12.8V (fully charged) if measured with a decent meter across the +/- terminals of the battery. It will of course dip under load and just after starting, but the alternator should have fired up by then and putting a healthy charge back in and certainly should be charging (albeit not as much) even at idle.

cheers,
george.
 
Typically on old school alternators/regulators, the 'idiot light' is actually a key part of the system. It provides a current path (so it really needs to be an incandescent bulb...) to initiate the field startup. As the alternator spins up the field generates itself and the field voltage increases so that the +ve value on one side of the 'idiot light' is close to the same voltage as the other side of the bulb (ignition +12V) and the light goes off.

Battery voltage should be near 12.8V (fully charged) if measured with a decent meter across the +/- terminals of the battery. It will of course dip under load and just after starting, but the alternator should have fired up by then and putting a healthy charge back in and certainly should be charging (albeit not as much) even at idle.

cheers,
george.

Hello,

x2.

Get yourself a meter and check across the battery terminals. That is a far more reliable number. Repeat every three months.





Juan
 

Users who are viewing this thread

Back
Top Bottom