Glow plug Test

[Chevybrit]

Found a good video on testing the glow plugs .. Difficult to tell visually but the multi meter will confirm a good one or bad..

https://www.youtube.com/watch?v=4Po_1pNHE1Y

I've read that when load is applied the voltage switches to 12v from 24v, and that if one is faulty more voltage goes to the remainder.
My question is does that mean MORE than 12v is going to the rest of the GP's? (Hence why many will fail quickly after the first)
And what if anything does that mean for a system that is converted to 12v?
PS I know that the OEM ones are the only 24v and the rest are 12v
Thanks

 

[MarcusOReallyus]

I've read that when load is applied the voltage switches to 12v from 24v,

Well, it's not accurate to say that it switches, but yes, it does drop from 24v to 12 when the current flows to the GPs.

and that if one is faulty more voltage goes to the remainder.

That is correct.

My question is does that mean MORE than 12v is going to the rest of the GP's? (Hence why many will fail quickly after the first)

Exactly right. With each failure, the voltage applied to the remainder goes up, which means they get hotter, faster, which shortens their life. That bumps the voltage again to the remainder, and so the problem gets worse each time.

And what if anything does that mean for a system that is converted to 12v?

Nothing. Once you convert to 12v (or just remove the resistor bank), this cascade failure no longer happens. It's purely a result of using the resistor bank in series to reduce the voltage from 24v to 12v.

PS I know that the OEM ones are the only 24v and the rest are 12v

Not sure what you are saying here. The original GPs are 12v GPs. That's what's specified for these trucks.

 

[Chevybrit]

Thank you Marcus, I pulled all mine today and tested them they are all 0.8 /0.9
I ordered a spare set of 60G's for the future.
I would like to start assembling the parts needed to convert my converted 12v back to 24v.
I'm reading through the Rosscommon PDF and hopefully the PO followed it to the letter and the re-conversion will be a simple one.
I noticed the fast idle had been disconnected too the other day .. not sure why someone would have done that?

 

[MarcusOReallyus]

Lots of us have the 24v start, but have bypassed the resistor bank to feed 12v to the GPs, to avoid cascade failures. Of course, Rick (cucvrus) sneers at us, since he's never had a problem and he can recognize when one GP is going bad, and just changes the bad GP right away.

So, either way works.

 

[Mainsail]

Lots of us have the 24v start, but have bypassed the resistor bank to feed 12v to the GPs, to avoid cascade failures.

This is what I've done. The only 24v on my truck right now is the starter, the landing lights, inverter, and the go-light spotlight.