[Guy Hiltz]

I need a little help.I have replaced the alternator and battery in my big block powered Monte SS but the factory in dash amp gauge reads on the low side.The car starts OK and the lights dont dim and all connections look to be OK .When I turn on the lights or heater the gauge drops even lower.I dont have any diagnostic equipment and was wondering if these cars(1986) are known for having gauge malfunctions.Thanks!

[bracketeer]

There are three wires on the alt, large red, small red, and usually tan or white. Using a 12 volt light bulb, run a wire from the tan/white wire connection to the light bulb and from the bulb to the battery positive. With the vehicle running the light should go out. If it does the gage is bad. If it does not the alt is not charging.

[docvette]

Docc here,

Get a DMM and measure the Voltage across the battery at Idle, after a few minutes after startup (to regain surface charge) It should be 14.4 volts and steady..

Next turn on all electrical and monitor does it hold steady at 14.4? (or no less than 13.75) If not the regulator may be the issue..

Even if the Alternator Is brand new, The failure rate out of the box on those is unacceptable..like 1 in 3 or 5...SO just being new does not take it out of the troubleshoot loop...

Unless your running TONS of Electrical accessories, you should not SEE a dip in power through the lighting systems (dim, then bright Ect..) UNLESS the alternator is under-matched for a full current press...

..............................

Doc