m-tdi coolant glowplugs

[blackdogvan]

I'm wondering about the coolant glow plugs on my mtdi build. I'm behind schedule after finding 3 busted piston rings & a siezed crank with bass ackwards crank journals on my rebuilt motor...

Have many mtdi folks bothered with these gp's? How are they being controled? I'm thinking if I do it it'll be with the same thermo switch as the normal GP's to kick them off once the coolant has started to warm up. The question I have is how to wire the control to the coolant GP relay such that its off when the key is in & the engine isn't running & off while cranking. Kinda like the headlights....

Any thoughts?

[the caveman]

Normally they are triggered by the coolant temp, through the ECM. But it would be easy to wire up a relay , and switch to trigger them when you want. You could even use 2 or 3 relays so that you could control 1,2 or 3 just like the factory setup. I have a brand new relay for them i would let go at my cost if you want. You would just have to use 1 or 2 switches to light it.

[Vincent Waldon]

Yup, you want 'em off for sure while you're cranking.. even on Vancouver Island!

"Twere me I'd probably not worry much about turning them on in various configurations... I'll see this winter but my understanding is that they're not stunningly effective individually... so perhaps a simple configuration: 

- dashboard switch powered downstream of the load reduction relay ("X") circuit
- that drives a 40A fused relay under the hood
- that drives all three coolant plugs  ??

[blackdogvan]

C'mon now Vince, we had a whole week last winter below -10 C!! That said I grew up on the praries & -5 & high humidity feels WAAYY colder that a nice dry -20.

For sure the relay power after the load reduction relay, I'd like to find a way to do it full auto, no dash switches & on after the motor GP's do their thing. I suppose a dash switch with the temp switch would make leaving them on accidentally impossible.

Kinda starting to sound like a Rube Goldburg GP setup...

[Vincent Waldon]

No problem then... op-amp comparator off the coolant temp sensor to drive the relay. 

Two set points... a "come on if the coolant temp is below this temp" point and a "turn off once the coolant reaches this temperature" point ?