OP
Dropping volts when running
- Thread starter Boooosted strangler
- Start date
If you have a multimeter, hook it up to the battery while its running, take a note of the voltage. Then, backprobe the field control wire and jump 12 volts to where the field wire plugs in. You're giving it full field by doing this, so don't hold it there for more than 5 seconds or so. The moment you give it 12 volts, your multimeter should jump to above battery volts. Probably 14-15 volts or so. Not sure, but for sure it will be above 12. If it does do this, it means you either have a bad PCM, or a broken wire from the PCM. I'd use an incandescent test light to jump the 12 volts from battery. It won't spark or screw anything up because of the load of the test light.
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I may be full of crap. I just saw yours is a 97. I'll have to search for prints to see how yours is set up.
Either way you should be able to stick a meter on the battery and jump 12 volts to the field. It's an old trick.
OP
I did continuity test on it from the PCM to the alternator was good and all the wires in between but I am down to try your trick for sure thank you!!! Mama just summons me in there to perform marital duties , so I'll be back out in the garage in 35 seconds flat and we will see if I can jump 12v thanks guys I appreciate your help !!! I'm over this non charging issue, I want to go lay I to that damn thing!!!!
Just make sure you get a meter on it in DC Volts when you start it. I'm looking for a wire diagram for your rig. So far the earliest year I can find is a 98. Not sure if that alternator set up is the same or not, but I'll keep digging.
I'm reading the theory on the 98. Can't find a 97 but I think its the same set up. Yours works by the PCM varying the ground path. If I'm reading it right, it means that 12 volts is at the alternator all the time, and when the PCM senses it needs more volts, it creates a ground inside the PCM for a moment and then opens it back up. Jumping 12 volts to it won't work. Yours is different than my 06.
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I remember the "angry bird" stage.......
Then the "Power rangers" stage.........
The "toy story" stage was way early....
And then..........
If the print below is the same on your rig, K72 (Dark Green/Orange Stripe) should have a steady voltage on it while running. Verify signal voltage is present with your test light or multimeter on K72 with the Jeep running. K20 (Dark Green) is the PCM giving that field voltage a ground when it senses it needs more juice. So, hook up the meter to the battery, and give K20 a ground with an incandescent test light (you're pretending to "be" the computer). The minute you ground it out, you should see the Multimeter that's hooked up to your battery jump in voltage. We're still jumping the field circuit, we're just jumping it to ground. Again, the second you give K20 a ground, you're giving that alternator full field. Keep it there too long and you'll fry a good alternator.
I also wonder if you may also need to do some checking of your battery temp sensor. You added a lot of heat under that hood with a turbo, and I wonder if when it gets way hotter, the temp sensor gets hot. The PCM thinks the battery is overheating, and quits charging it. Just a theory. If that's the case, you could remove the sensor and install a resistor in its place instead. Testing the alternator by giving it a ground will dictate the next steps in troubleshooting.
In your original post, you said you were dropping volts, noticed the black field wire connector was melted, and replaced the alternator. Are you 100% sure that there isn't something melted inside that plastic connector, and the original alternator you replaced was actually ok? You said you checked the wires to the PCM but I had to bring it up.
Lots for you to chew on but I wanted to get it all down cuz it's bedtime! Good Luck.
I also wonder if you may also need to do some checking of your battery temp sensor. You added a lot of heat under that hood with a turbo, and I wonder if when it gets way hotter, the temp sensor gets hot. The PCM thinks the battery is overheating, and quits charging it. Just a theory. If that's the case, you could remove the sensor and install a resistor in its place instead. Testing the alternator by giving it a ground will dictate the next steps in troubleshooting.
In your original post, you said you were dropping volts, noticed the black field wire connector was melted, and replaced the alternator. Are you 100% sure that there isn't something melted inside that plastic connector, and the original alternator you replaced was actually ok? You said you checked the wires to the PCM but I had to bring it up.
Lots for you to chew on but I wanted to get it all down cuz it's bedtime! Good Luck.
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OP
My Boy is currently in the Toy Story
My Boy is currently in the Toy Story stage. Loooooves him some Buzz.
My Boy is currently in the Toy Story stage. Loooooves him some Buzz.
stage. Loooooves him some Buzz.
OP
Sooo with summer hitting , getting boat ready and out, camper ready and out , and obviously the Jeep out, I got my issues all dialed in it was the PCM , the whole time volt reg is in the PCM, OR ECU whatever is the right one...but after a few injector trial and error runs, I got her boosting up crazy like this ol girl was shakin and groovin waaaay faster than a jacked up Jeep on 37s needs to be going!!! But I loved every second of it!!!! But now all of the suddon I'm not building any boost at all, so gotta break her down and try to figure that out hopefully I can by Friday because bthere Is a big Jeep poker run and a car show/ cruise I like to show up and walk around after the Jeep run, sooo fingers crossed I didn't mess her up too bad, aka blew head gasket already... hopefully bits just something little I can fix and be on my way