Welp, just got done with the 3G upgrade. Started the cat up and checked the voltage. Had 14.7 steady. PAPerformance says their alternators should put out 13.8 to 14.6 on the upgrade instruction sheet so I thought I was good. I did my cabbage patch dance and strutted into the house. I had the wife come out and restart the car, put it in drive, turn on the headlights and checked the voltage. Saw the taillights zip across. Solid 14.7. Then I told her to shut it off but the car wouldn’t shut down. Come to find out I could read voltage at “I” of the starter solenoid with the igntion switch in off. The solenoid is toast.
I put this solenoid in about two months ago so maybe it was defective. I still have my old one to put back in. My fear is that the 14.7 was too much for the relay and will fry another solenoid sooner or later. Or worse 14.7 will cause other problems. The only thing I can think to do is get a larger pulley wheel. Kind of hacks me off though I dropped two hundred for an alt from mustangs unlimited that is supposed to be plug and play. Totally new with the same diameter pulley, dimensions as OEM, etc…
Any thoughts?
Might be the ignition switch itself, the electrical part. I had the same problem, car would not shut down even with the key removed. Replaced my battery ground wire (just cause it needed it) and ignition switch and the problem went away. And still using the same solenoid, which was also less than a year old at the time.
I pulled the wire off of “I” and read continuity from the battery post on the solenoid to the “I” post, which you shouldn’t have with the car off. I will call PAPerformance in the morning and talk to them. I wouldn’t think that .1 volt would cause problems but I want to be sure. I would like to drop it down a half volt to be on the safe side though. The old alt pulley read 2.66 outside diameter. The new 3G pulley reads 2.62 outside diameter. Could that little bit make a difference?
Pulley diameter wont change anything. If anything, it would just lower the amperage output, but not enough to notice. I am thinking ignition switch as well.
did you unhook any cables from the solenoid when you where installing the alternator?
Sounds like the nuts could have been too tight on the solenoid. the solenoid will take 14.7 all day as the power should only run through the solenoid when you are starting. The rest of the time it goes to the battery or the vehicle.
Ok so can someone explain the hold in circuit on the starter solenoid then? The “I” wire. Doesn’t that take 12V from the battery while the car is running and send it straight to the coil? So the way I see it the solenoid is always “kinda” energized.
The “S” wire energizes the Pull in coil in the solenoid to send 12v to the starter. It deenergizes once you let go of the ignition switch.
Just read an article in mustang forums, may have to add in a resistor to lower the exciter voltage. Will check with PA tomorrow. I’m exhausted and I smell like old car. Wonder what the wife will think when I crawl in bed…
I’d have to check the wiring diagram, but I’m pretty sure the I connection doesn’t go straight to the coil. The feed to the coil comes from the firewall, through the ballast resistor, from the ignition switch, passing through the tach on the way if you have a tach, right?
If there was always 12V from the solenoid to the coil, not passing through the ignition switch, that would both kill your battery and also burn out the coil, no?
Looking at the ignition diagram it shows “I” wire # 262 going to a connector and meeting up with 16 and 16A (pink wire). 16 goes straight to the coil. With the key out of the ignition I had 12V at coil until I pulled the “I” wire off the solenoid.
Also looking thru old threads I see a few guys who got 14.7 after they installed the new Alternator.
The I connector (wire 262) isn’t supposed to be providing 12v to the coil, the voltage to the coil (less than 12v, assuming the pink resistor wire is doing its job!) comes from the ignition switch through the pink resistor wire, right? So if there is 12vdc between your solenoid’s I connector and ground, without wire 262 connected there, then that suggests a problem with the solenoid?
Please note I’m using question marks all over the place. The reason for that is I don’t understand what the reason for wire 262 and the I terminal on the solenoid are doing. I’m actually gonna have to go read about that right now cause it’s bugging me.
That was easy. Wire 262 is there to take a full 12v from the starter solenoid only while the starter is engaged to bypass the resistor wire, giving a full 12v while cranking instead of the lower ~8v through the resistor wire during normal running. So if you were continuing to get 12v out of the I terminal even when the key wasn’t in the start position, then that suggests the solenoid is indeed shot. Maybe you just got back luck with the new one you put in? If the starter motor was still cranking even with the key out then the problem might be in the ignition switch, since it would still be energizing the coil in the solenoid. But if the starter was disengaged, that suggests that the problem was the solenoid continuing to supply 12v out of the I terminal even once the coil in the solenoid was not energized, so, a malfunction in the solenoid.
I think I got that right.
The I connection provides 12 volts to the coil during cranking, that is when the starter motor is engaged. The idea is to supply more voltage to the coil while you are trying to start the car. During cranking the system voltage will drop due to the internal Equivalent Series Resistance of the battery. Basically the amount of current is ,limited and since current is limited, the voltage drops over the load of the starter motor. So what is ordinarily 12.6 volts drops to perhaps 8 volts or sometimes less during starting. IF this 8 volts was further reduced by the series resistance of the ballast resistor wire going to the coil, the actual voltage at the coil would be quite low. The I wire should only show battery voltage during cranking.
Increasing voltage increases the distance that a spark can jump. My guess is that the higher voltage allowed a spark to jump an already slightly compromised solenoid and it welded the contacts.
Called PA this morning. Ford 3G alts are set at 14.8 output so the alt is working just fine. I reinstalled my old solenoid and the car started and shut down just fine. The old solenoid reads across the batt post and the I post on the bench so thats ones going in the trash. Just going to chalk it up to a crappy new solenoid and press on. In retrospect the older one does seem to be better built with longer posts. I will clean up the wiring today and tighten the belt to get rid of the squeel at startup.
Just for giggles I did check the voltage at the coil again this morning and got 13V. I thought the pink wire was supposed to drop that down to half that???
Until you put a load on it (current passing through the circuit) it will show the higher voltage. Start it up and you will see the lower voltage.