You may be right. I tried to follow the glow relays external wiring on my hayes schematic. I Did not complete the task yet. Afterglow was not factory equipment till the nineties I thought unless retrofitted.
I was a little suprised with the requirement for four feeds to control the relay. . Plus the heavy 12v feeder.

Either my eyes have dropped off more than I thought or that hayes manual wiring schematic is a poor faded printing. I guess it's time I spent some money on factory service literature.

If what you say is true than it is more likely to be a bad switch. As you release the key from starting the switch goes back to the same position as was used to activate the glow plug relay initially. So there would have to be some kind of mechanical latching system incorporated in the switch or relay external to the switch to prevent re activation of the glow relay with the switch travelling backwards. That mechanisim or relay if there is probably his problem.

His glow plug relay comes on line again in a random fashion. It manages to close up something again with running vibration if mechanical. I wish I also had a detailed schematic of the insides of the relay itself. The haynes only shows basically a power type transistor and relay with no description of the timing circuit or how those four leads service it.

Last night I was trying to determine exacly how the re activasion was normally prevented by design. Yet without enough information could not tell.

Since his car had the battery going flat etc. Plus his new used test relay was functioning normally in his other car. It is fairly safe to assume his present glow relay is not the problem.

At least the electrical portion of the ignition switch was only thirty dollars he mentioned. That seemingly reasonable price did manage to suprise me.