CS130D Alternator Idiot Light not working
05-28-2019, 12:56 AM
#1
CS130D Alternator Idiot Light not working
I have a pigtail on my CS130D alternator that leaves me with an "L" terminal and a "FR" terminal. The L terminal is for the idiot light, and the FR terminal (sometimes called just an F terminal) is for the external field monitor connection (which I don't know if I should be using because I don't know if my alternator uses field control).
The idiot light is an LED bulb on the inside that has one end connected to the fuse box's 12V+ IGN source (with an inline 5A fuse), and the other end of the bulb is connected to what should be the L terminal on the alternator. The problem I am having is that the idiot light won't turn on when the key is flipped to accessory and the engine is off. The only time the bulb will turn on is when I plug a 12V+ Constant Hot wire to the FR terminal (which I don't think is required). When the 12V+ Constant Hot wire is plugged into the FR terminal on the alternator, an audible humming noise comes from the alternator even when the key is in the off position. This isn't ideal because it'll drain the battery (and god knows what else).
How do I get this idiot light to let me know when the alternator isn't working properly?
The idiot light is an LED bulb on the inside that has one end connected to the fuse box's 12V+ IGN source (with an inline 5A fuse), and the other end of the bulb is connected to what should be the L terminal on the alternator. The problem I am having is that the idiot light won't turn on when the key is flipped to accessory and the engine is off. The only time the bulb will turn on is when I plug a 12V+ Constant Hot wire to the FR terminal (which I don't think is required). When the 12V+ Constant Hot wire is plugged into the FR terminal on the alternator, an audible humming noise comes from the alternator even when the key is in the off position. This isn't ideal because it'll drain the battery (and god knows what else).
How do I get this idiot light to let me know when the alternator isn't working properly?
05-28-2019, 08:44 AM
#2
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Re: CS130D Alternator Idiot Light not working
Use IGN+ switched power to the FR terminal.
The humming sound you hear with constant +12 to the FR terminal is normal. You are energizing the field coil.
RBob.
The humming sound you hear with constant +12 to the FR terminal is normal. You are energizing the field coil.
RBob.
05-29-2019, 03:18 AM
#5
Re: CS130D Alternator Idiot Light not working
I plugged the indicator light into the FR terminal instead and it works perfectly now. 
What is the point of the L terminal if it's really the F terminal that is responsible for the light working?
What is the point of the L terminal if it's really the F terminal that is responsible for the light working?
05-29-2019, 08:08 AM
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Re: CS130D Alternator Idiot Light not working
Typically, GM uses the L terminal for the dash idiot light. This is done when there is no voltage gauge. There needs to be around 470 ohms of resistance in this feed in order for the alternator to charge, and not burn up the regulator.
On cars with a voltage gauge in the dash the F terminal gets IGN switched power. The required resistor is built into the alternator.
RBob.
On cars with a voltage gauge in the dash the F terminal gets IGN switched power. The required resistor is built into the alternator.
RBob.
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