Hi all,
I have a gear driven 12V alternator on my T which is brand new. I have also recently replaced all my wiring. The issue I have is that My T only starts (electric start motor) with the alternator disconnected. The moment I connect the alternator nothing happens anymore.
Any help would be greatly appreciated.

Thanks, Paul.

I suspect you are not using the normal starter foot switch and heavy cables but likely using a solenoid. Too much here to guess about. What on the car is NOT STOCK since on a stock T the charging path has nothing to do with the starter power path and they only connect together at the battery circuit. You might want to start by telling us what year the T is and what else on the car is not stock. Maybe post some detailed pictures of the motor compartment since guessing isn't what you really want us to do.

Hi John,
Indeed I am using a solenoid at the starter. Could that be the issue ? Wiring harness ('26-27) purchased at Lang's for a distributor set up.
Checked the wiring diagram and connections several times.
Can send pictures tomorrow if needed.

Paul

Paul, this is the kind of trouble that can happen when a T is altered. Unlike the original system there is no tried and true official method of running an alternator on a T. Like John said there will be a lot of guessing in figuring this out. Do you know if your magneto is operational? You might want to consider using the original set up.

Hope you can get it worked out.

Check the alternator wire hook-up to the firewall block and make sure its in the correct place. Most 6V solenoids should have one lead on the front of the unit going to power (the foot switch) and the other going to ground. If there isn't two small terminals the solenoid is internally grounded. Normally you wire the foot switch with one wire going to battery power side (fused preferably)of the solenoid and the other going to the small terminal on the front of the solenoid. If there's two small terminals, the other is wire to a ground. The other large terminal on the solenoid is wired by large cable to the starter. I've used this type of system for years with no problems at all. While you're at it, make sure your ignition switch is hooked up correctly according to the schematic.

Just looked at the first part of the post and its says 12 Volt. !2 volt solenoids work the same way and are wire the same way.

What model year is your car, swapping out the generator for a alternator should not change anything, going to 12 volts can add a few wrinkles,are You using the original foot switch to activate the solenoid or a after market ignition switch, when you start making modifications its not always plug and play, I am surprised something has not got hot and started smoking, and if You don't have a main fuse I would add one before proceeding, A cheap 6/12 volt test light is a must have when checking auto electrical problems better than a volt meter for most checks, Need to find a good auto electric guy to help You, many very good mechanics are not well versed in solving electrical problems.

I am assuming that everything is wired up correctly. That would be the first place to check.

If everything is wired correctly, then check the voltage at the hot side of the solenoid when starting. If it low, for instance 8 volt for 12 volt system, then there is not enough voltage to pull in the solenoid. Very possible the alternator is draining away the voltage. If you have a two position ignition switch, you could start on one position and then switch to the other for running, with the alternator wired into the second position. I am assuming you have a distributor.

I have an alternator on my car, which works great and is very reliable, but I have the direct acting switch on the floor for starting. There may be something wrong with the alternator. Does the alternator charge OK after the engine starts? Check the resistance from the hot lead on the alternator to ground. If very low then that is where your voltage is going. There are rectifiers in the alternator which should prevent a path to ground when the alternator is not charging. It could be that you have a bad rectifier.

I would suspect that one of the wires on the alternator is connected to the ignition switch. It might be grounding the wire connecting to the ignition coil and distributor which would eliminate your spark.
Norm