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I bought a non running 91 RS 5.0 tbi with a locked up L03 ..... replaced the long block and it runs fine ..... but the alternator and starter wiring have me stumped!! The alternator puts out .03 v on the large post when running, if you jump the red wire to the post it will engage the starter. I looked at the starter wiring assuming I had put a wire where it didn’t belong , but can’t find anything out of the ordinary.. there is a purple wire and an orange wire on the solenoid and along with the large battery cable there is three wires on that post ....... i removed the orange wire from the solenoid and put it on the distribution block next to the battery assuming that’s where it went , and when I did that along with jumping the red wire to the alternator post nothing happened, this is where it just gets crazy!! While in that configuration I pulled the positive battery cable off with the engine running and the alternator came to life putting out 15v . Any help would be appreciated and any info as to exactly what wires go to the starter on both posts would help a ton Here’s a picture of the alternator
I pulled the positive battery cable off with the engine running and the alternator came to life putting out 15v .
Matt , don't ever do that again !
Back in the good old days when there were no "Semiconductor" devices in cars , pulling a battery terminal on a running engine to check for charging was an acceptable test method . But then along came transistorized radios , and then transistorized voltage regulators and ignition systems , and before ya knew it along came transistorized fuel delivery systems . All this happened over time , starting in the late 1950s and by the end of the 1970s pretty much all cars had transistors in all of those applications . Now as we electronics hobbyists know , the bane of any semiconductor device , other than heat produced by overloading , is the "Voltage spike" . Suddenly , instantly , raising the voltage appreciably above the normal operating voltage of the device can result in the destruction of the "Semiconductor junction" . Now , here's your car running at a certain voltage , let's say in your case it was low 12 ish volts . When you pulled the terminal off and read 15 volts that 3 volts don't sound like much , right ? Well , for a few milliseconds after you broke the connection the actual voltage likely spiked much higher than 15 volts , and that spike can be damaging to all the devices I mentioned . Does it ruin stuff every time a battery terminal gets pulled on a running engine ? Of course not . In fact , I'll bet you could pull it quite a few times before frying any delicate little transistors . But CAN it happen that the pulled terminal fries something ? Oh Hell yea , it sure can , and there is no need to take that risk .
02-22-2019, 07:30 PM
Matt , don't ever do that again !
