Glow plug connector idea
- Thread starter Selahdoor
- Start date
Macrobb
Full Access Member
So, something I've learned:
If you have too high resistance, AKA, your glow plugs aren't drawing enough power, your controller will short cycle, because it thinks they are hot.
It's measuring the resistance/current using that metal zig-zag piece on the controller.
So, if you want the controller to think the plugs are cooler, therefor drawing more power, you need to increase the voltage across that zig-zag piece. You do this by increasing the resistance of that piece.
How do you do that? By changing the cross-section. I found that taking a "junk" Motorcraft controller that short-cycled, pulled the zig-zag off, ground a 1/16" deep notch right next to the "hole" in the center(the highest resistance spot in the resistor)... and hey, it cycles longer! Been running it for a couple months now, really happy.
Using that method, even if your new harness or glow plugs are out of tolerance on the high side, you can fix it!
(if you need lower resistance, you would probably just do a resistor voltage divider to ground on the controller's "sense" wire).
If you have too high resistance, AKA, your glow plugs aren't drawing enough power, your controller will short cycle, because it thinks they are hot.
It's measuring the resistance/current using that metal zig-zag piece on the controller.
So, if you want the controller to think the plugs are cooler, therefor drawing more power, you need to increase the voltage across that zig-zag piece. You do this by increasing the resistance of that piece.
How do you do that? By changing the cross-section. I found that taking a "junk" Motorcraft controller that short-cycled, pulled the zig-zag off, ground a 1/16" deep notch right next to the "hole" in the center(the highest resistance spot in the resistor)... and hey, it cycles longer! Been running it for a couple months now, really happy.
Using that method, even if your new harness or glow plugs are out of tolerance on the high side, you can fix it!
(if you need lower resistance, you would probably just do a resistor voltage divider to ground on the controller's "sense" wire).
saburai
Full Access Member
Those look beautiful Wes!
How do you have the manual conversion set up? Three position switch? Off/factory auto/manual?
Thewespaul
Full Access Member
Thank you, you can read up on all the details here: https://www.oilburners.net/threads/...ssic-diesel-designs.84824/page-2#post-1017186
saburai
Full Access Member
Yep, was just doing that now, but many thanks for the quick reply and link.
Someone needs to come up with a controller that goes strictly off engine block temperature. Time versus engine temp. If it was plug and play I bet it would sell like hot cakes.
chillman88
Full Access Member
Isn't that how the early 6.9 was set up? I know the controller screwed into a coolant passage.
Not sure about that.
IDIBRONCO
IDIBRONCO
I think that may have been the idea behind the design, but, as we all know, those controllers were known for going out. Hopefully the technology has improved during the last 30+ years so something new may work better.
The_Josh_Bear
Full Access Member
If you're that worried about the GPs cycling a few extra times a week then you could always run the controller wire through a relay that opens once the coolant is over some temperature you desire, say 125*? All that takes is a coolant switch around that temp and the relay. Would cost maybe $25 and wire+time. The coolant port in the rear of the passenger head is just a plug for most of us, ready to use. 
Personally I went manual GPs with a momentary switch and it's been perfect for ~5 years. Starts fine to down to single digits, just gotta hold it for 15 seconds. And in the nice sunny weather only needs 5-6 seconds.
Personally I went manual GPs with a momentary switch and it's been perfect for ~5 years. Starts fine to down to single digits, just gotta hold it for 15 seconds. And in the nice sunny weather only needs 5-6 seconds.
