My 1979 W123 300D is presenting a major problem related to the glow plugs.

I was having starting problems in the cold weather, and so replaced the glow plugs with OEM Bosch components. The engine will still not start, and the glow plug light remains on much longer than normal--about 60-90 seconds.

While troubleshooting the light issue, I happened to look under the hood and noticed that, approximately after the time when the glow plug light would turn off (20-30 seconds) the connector rails between the glow plugs are glowing red hot! I must assume this is not normal.

Are the glowing connectors due to the glow plug light remaining on, possibly due to a stuck glow plug relay?

I always believed if the relay was bad, the light would not come on at all.

Any help will be very much appreciated.