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Hi everyone
Working on testing a 2005 GMC Envoy computer controlled alternator ---- It has a 5 volt PWM ground side switched circuit.
Can I test the 5v PWM feed circuit and control wire with a 150mv testlight while engine running. (Feed side to T/L ground and cotrol side to T/L battery)
How about full fielding the control side with a jumper wire.
Hey joecar! You can use a test light on the Generator L and F terminals on your Envoy, but neither is going to light the test light bulb.
The Generator L isn't PWM, just a solid 5V signal to enable charging. The alternator will ground the L terminal to make the battery light come on. The Generator F is PWM by the alternator, but only serves as an input to the PCM to indicate alternator load.
You could use the test light on the L terminal to pull the 5V to ground and make the battery light come on, showing circuit integrity. But there isn't enough current on that circuit to light the test light bulb.
Neither circuit can be manipulated in a way to full field the alternator. The only way you could do that would be to add loads to the system with the engine at 2,500 RPM and measure alternator output current.
