Good afternoon,

Purchased a 79 300TD almost a year ago, and having some electrical bugaboos since then. I've come to the conclusion that my glow plug relay is intermittently not shutting off power to the glow plugs after I start the car. Sometimes--only sometimes--I will drive a ways, park, go to restart, and my battery is dead. Other times, I have no battery issues for stretches. I've also had issues like the electrical components in the car not functioning properly, headlights dimming, etc. I've replaced the alternator with a known good one, and I know my battery is good.

Has anyone ever had this issue ? Part of my concern comes from the fact that someone did some rewiring on the small plug that goes into the dash from the glow plug relay. I'm more familiar with the post-1980 relay. The 1979 relay has five wires (green is the odd fifth one). My pre glow indicator light has never lit up since I bought the car. I've checked all glow plugs and they're good. It was updated to parallel style plugs, so I think someone just rewired it funny.

Questions:
1. What color is my indicator light wire supposed to be ? (I know it's blue with white stripe on later models.)
2. What does the green wire do ?
3. The engine has two temp sensor ports on the head next to the IP, but for some reason I have four temp sensor wires in the engine bay - two from the dash, and two running along with the glow plug wiring. What is the correct configuration of the temp sensors on this car ?

Just need help understanding the glow plug system on the pre-1980 diesels.

Thank you kindly.


Wallace