GPR sticking on, help trouble shooting
 

My glow plug relay is cycling on and off as the car is running. I have a good used relay in their now, but the last one I had in there stuck on so long it killed my battery and melted the relay.
Could this be because I have the Neutral Safety Switch bypassed? I permanently jumped the purple wires above the throttle pedal.
If not what else could be causing this?
Strangely, I was running the car with a GPR out an 87(till the right part came in) and I had no problems with the plugs turning on while driving.
Could my relay be bad, is it the NSS hack, or something else?
Thanks
Samson

Turning on the key signals the relay to activate. If the "ignition" switch is wonky, it might be joggling over bumps and activating the relay inadvertently.

if the ignition switch is bad then why does it not happen with the om603 Glow plug relay?

A stock 87 GPR has no afterglow, in other words, 30 seconds after turning key to 'on' it cuts out. It cuts out sooner if you twist the key to crank within that period. This is the only way it comes on, and the only two possible ways it turns off. Never comes on again for the drive cycle. When everything is healthy.

Later GPRs have an afterglow. The 'violet' wire you're talking about has an effect with afterglow.

Do a search on this forum on terms: afterglow modification.

Also, I made a very simple GPR mod that shows when the GPR is actually supplying power to the plugs using your dash indicator for glow plugs. It will show if the relay is sticking, and any time it "reactivates" on its own if it should happen to.

Here:
http://www.peachparts.com/shopforum/diesel-discussion/314706-easy-glow-plug-relay-mod-better-dash-indicator.html

Whether it cuts out sooner or later depends on how long you crank. "Cut out" occurs when the key is released from the start position.

Thanks a ton Scott. I actually found those threads while researching this problem. bought the 47 omhs resisters and when I opened up my glow plug relay it was way different than in your post so I couldn't do the mod.
Also, I thought all the old 5 cylinder GPR(circa 123s) would not have had after glow potential.

could we be talking about different purple wires? My NSS was shot, and the part was on back order, so I read up on how to bypass the switch, jump two wires above the throttle pedal in the passenger compartment. And that's what I did.
As far as the afterglow mod, I'm looking for the opposite. I want to disable my glow plugs, to keep them from glowing on their own after the car is running.