Matt Clawson

Hello everyone i'm going to describe in detail as much as i can what is going on.

I replaced the starter with a mini high-torque MSD unit to help to over the car that has work done to it (Cam / Heads / Intake / Headers ect ect). During that process i was a dummy and hooked the wires up backwards and noticed when i put the negative battery cable on and the starter spun up without turning the car on. I since then reversed the wires and all is good with the starter.

NOW to the problem.
I am getting a service charging system fault and the car is not charging at all. I have checked my battery (10 month old Optima Red Top). I have also pulled out the alternator and had that bench tested and even replaced. Still no go. I have checked the Horn fuse and battery fuses under the hood (60 and other 15 amp fuses). That did not do it either.

So what i'm seeing is, with a multimeter the battery is reading the voltage that it has in the cells, but when the car is turned on i'm receiving no jump in volts what so ever. Next step i test the alternator. With the car off 0 Volts, with the car on 0 volts. So the alternator works on the bench, but not on the car. Shouldn't i be able to read the 11.5-12 volts off of the main positive wire on the back of the alternator from the battery at a minimum? I've also checked the tightness of the starter solenoid wires and they are all tight and the car turns over great and starts quickly. So i don't think they are loose at all.

So next questions, yes i have read that spark plugs can cause charging issues, but i haven't ever had a problem before so i don't think that is it. Is there a fusible link or something between the battery and alternator that could have popped? I do not want to take the car to the dealer here, i really distrust their work from previous experiences.

Ideas?

Matt

Bill Dearborn

Reversing the polarity on the starter may have wiped out the fusible link in the wire going from the battery to the alternator. Here are the charging and starting schematics. They show a slightly different view of the fusible links.

Charging Schematic with arrow pointing at fusible link.


Starting Schematic with arrow pointing at fusible link:



A blown fusible link would explain why you can't see the battery voltage at the alternator positive terminal. It isn't attached to the positive battery terminal any more.

Pull the positive battery cable from the battery and the other end off the alternator and see if you get continuity through the cable. If not the fuse is blown.


Bill

C6topless

Being you can start the Vette and have checked out the individual parts ( alternator, battery, starter) I can safely say that you have likely fried a fuseable link. Get out the ohm meter and test the resistance of your cables.... the one that has extremely high resistance will be the one with the bad link.

I am willing to bet when your vette is started the voltage on the inboard gauge sits static at nothing higher than 13v and then each progressive start, it falls a little lower and lower. That is symptomatic of when your alternator or its cable is faulty.

This is not a difficult fix -- if you were in Cali, I could have it fixed in about 20 mins.