Not necessarily the worst case
Davy, you may not be SOL on this.
The reason the motor works fine once it is spinning is because it is really two motors in one - a motor to start things turning and one to keep them going once they start.
The starting system on your motor has failed. It may be that a winding has failed and that means the motor will have to be "rewound" by a shop (shouldn't be a big problem).
But there are a couple of things you can check before you assume the worst.
First, the starting sequence involves several components, all subject to enormous stress and strain. Depending on the motor and where in the US it was meant to work you will have at least one capacitor. If it goes, or a wire breaks it could cause this problem - bad capacitors have been known to take other components with them, so you should really replace it/them after all these years in any case). Now before everybody jumps on the "two capacitor? not done" bandwagen, we had a few rollermatics which were set up with two in our dorms. Low voltage and lots of starting loads at once. So don't assume, check. Please remember, a capacitor still has enough charge to kill you or ruin components even after the plug is pulled. Discharge it before you handle it.
Second possibility. The motor may have a centrifugal start switch that has failed. A loose connection or broken part or contacts not touching...many things can go wrong there and with a simple VOM, you can track them down.
Third possibility. Over time, corrosion and wire breaks can leave one wire dead when the one just next to it is still resistance free and working perfectly. Check all the wires in the harness and the connector blocks. Did someone decide to splice something in at some point? Did a wire get pinched?
The schematic diagram may have the details on the two systems in the motor, if it is a standard (and I do belive GM was using standard motors by that point) then there will be a catalog with the data or someone here will know) so you can find out if it is a shorted/dead start winding.
By the way, the direction the motor runs is determined by the starting system, not the field windings. That is why you can spin it in either direction and once it starts, it stays on that way.
Davy, you may not be SOL on this.
The reason the motor works fine once it is spinning is because it is really two motors in one - a motor to start things turning and one to keep them going once they start.
The starting system on your motor has failed. It may be that a winding has failed and that means the motor will have to be "rewound" by a shop (shouldn't be a big problem).
But there are a couple of things you can check before you assume the worst.
First, the starting sequence involves several components, all subject to enormous stress and strain. Depending on the motor and where in the US it was meant to work you will have at least one capacitor. If it goes, or a wire breaks it could cause this problem - bad capacitors have been known to take other components with them, so you should really replace it/them after all these years in any case). Now before everybody jumps on the "two capacitor? not done" bandwagen, we had a few rollermatics which were set up with two in our dorms. Low voltage and lots of starting loads at once. So don't assume, check. Please remember, a capacitor still has enough charge to kill you or ruin components even after the plug is pulled. Discharge it before you handle it.
Second possibility. The motor may have a centrifugal start switch that has failed. A loose connection or broken part or contacts not touching...many things can go wrong there and with a simple VOM, you can track them down.
Third possibility. Over time, corrosion and wire breaks can leave one wire dead when the one just next to it is still resistance free and working perfectly. Check all the wires in the harness and the connector blocks. Did someone decide to splice something in at some point? Did a wire get pinched?
The schematic diagram may have the details on the two systems in the motor, if it is a standard (and I do belive GM was using standard motors by that point) then there will be a catalog with the data or someone here will know) so you can find out if it is a shorted/dead start winding.
By the way, the direction the motor runs is determined by the starting system, not the field windings. That is why you can spin it in either direction and once it starts, it stays on that way.
