Pontiac Problems? Ask a Mechanic for Answers ASAP
Ok, I need the vin number to pull the schematics for the charging system.
Also, do you have a voltmeter for testing?
Ok, give me a few minutes to pull the schematics. In the meantime, I need you to check the voltage at the battery with engine idling and all accessories off(lights, ac, radio). To do this, set your voltmeter to 12v DC. place the red probe end on the positive terminal of the battery and the black probe end on the negative terminal of the battery. Then repeat with a couple of the accessories on. Let me know the voltage for both tests.
Ok, if there is no DC setting then that voltmeter is only for AC, which is household current. If you can take a photo of the face of your voltmeter and use the paperclip icon on your reply box to upload to here and I can verify
hmmm, appears that it is only for AC voltage, ohms and amperage. We need one with a DC setting.
Ok, check and see if your blower for the ac/heater works on high. The high speed blower and alternator share the same fuse, so if the blower doesnt work on high speed it is a blown fuse, but if it does work, then that is not the issue
Look at where the leads plug into your voltmeter. For the red(positive) are there more than one place to plug it in and if so, does one say DC.
Ok, put the black lead in the COMMON hole, and out the red lead in hole on the right when looking at it(see attached)
Put the setting on 2 on voltage and take your readings
Ok, go to the 200 setting
Ok, at the alternator, you should have a red wire, orange wire, grey wire and a brown wire. We need to test the voltage of each wire with engine idling and accessories off.
Test one at a time. You will place the black lead on a good ground(negative battery terminal works fine for this), and then you will need to stick the red wire in back of the connector at the alternator where each wire goes into in order to get a reading. I need the voltage for each wire
So, just a grey and red wire?
How long have you had the car and how long has the charging problem been going on?
Ok, the red wire goes between the alternator and starter. The grey wire sends a signal from the alternator to the engine control module(computer) that then goes to the battery light.
The 2 missing wires are critical. The orange wire goes from the fuse to the alternator to supply battery voltage and the brown wire goes from the engine control module to the alternator and is what sends the signal to the voltage regulator in the alternator to energize it so that it works. Without this, the alternator will not put out enough voltage.
At idle with accessories off, it should be registering 13.5 to 14.7v at the battery
Both the 4 and 6 cylinder engines have the same 4 wire setup at the alternator
You will probably need to take the alternator off and look for hanging wires somewhere near it - one orange and one brown. If not anywhere near the alternator, then someone cut them really far back and from my end, it would be a guess on where they would have cut them.
The brown wire that goes to the ecm is actually a red wire at the ecm(they have a splice along the way and it changes color there). You will run from pin 74 on the BLUE connector at the ecm(see attached) to the L pin at the alternator connector(see attached wiring diagram).
The ecm is located behind and underneath the glove compartment(see attached)
The orange wire goes from the 30 amp fuse labeled HVAC BLOW MTR in the engine compartment fuse box(see attached) to F pin on the alternator
My suspicion is that once you run them, it still wont charge. I suspect that the internal circuit in the ECM that controls energizing the voltage regulator has failed and someone tried some type of workaround, of which there isnt one.
So just be prepared for the strong possibility of it still not charging after doing the wiring and having to get a new ECM.
You are welcome and have a great evening
ECMs are specific for year, make, model, engine size and transmission. Also, it will need to be programmed with your vehicle's vin number and mileage, which requires a Tech2 GM scan tool to do so.
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