I have put new zd9 glow plugs in my 6.9 IDI , changed the glow plug connectors, put a 7.3 glow plug controller, used one. It does not send voltage to the glow plug light but it seems to work, but it takes good 20 seconds before it starts cycling in temperatures around 50 degrees F . Honestly, I do regret swapping to the newer style system, as it seems to me the old style glow plugs glow way faster. The old ones were autolites, two had broken conectors but it needed to count to six and started right away. I feel the glow plug relay might be defective, I wired it on the momentary switch to prevent it from failing on. The Z strap on the relay gets hot to the point it is smoking, all connections cleaned. I do not feel it is normal. I am located in Europe, new glow plug relay ordered but it takes over a month. That is the only downfall of using American iron in Europe, the shipping costs are killing me more than diesel prices.

 

The newer glow plug controller is made to fail in the off state, unlike the early one.

The zd-9's will also outlast the zd-1's

Either way I think you made the right call changing it, once you get the little quirks worked out it should treat you right!

 

I had issues with my controller even with all new ZF9's, I ended up putting in a push button. I know some guys are saying the push button is a bad idea now, but it worked very well for me.