Manual Glow plug test idea
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Mountain Pass
Joined: Sep 2004
Posts: 143
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Manual Glow plug test idea
I was wondering since the spade style glow plug system will function with a few burnt out glow plugs, could a 12volt LED or a indicator light be wired inline with each individual glow plug? I would like the indicator lights to be set up in the cab for ease of use. Let me know what your thoughts are.
Posting Guru
Joined: Aug 2006
Posts: 2,175
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From: Kent WA
It would be pretty tough to do I think. At least on the older trucks like yours and mine.
I haven't used a meter to verify it, but I've read that the GPs are all wired in parallel. Combine that with the fact that the ground for them isn't even a wire - it is them being threaded into the block, and it gets even more difficult.
The only way I can see to do it is to insert your indicator between the GPs and the harness. Doing that would require that your indicator (bulb or LED) and the wires to it be capable of withstanding the 6-12 amps that needs to flow through each GP in order for them to work. Any resistance added to the circuit would also reduce the heating of the GPs as well.
The only other way I can see would be some sort of current sensing device, but then you'd be looking at some pretty complex electronics. Just doesn't seem practical to me. A good idea, but not practical.
I haven't used a meter to verify it, but I've read that the GPs are all wired in parallel. Combine that with the fact that the ground for them isn't even a wire - it is them being threaded into the block, and it gets even more difficult.
The only way I can see to do it is to insert your indicator between the GPs and the harness. Doing that would require that your indicator (bulb or LED) and the wires to it be capable of withstanding the 6-12 amps that needs to flow through each GP in order for them to work. Any resistance added to the circuit would also reduce the heating of the GPs as well.
The only other way I can see would be some sort of current sensing device, but then you'd be looking at some pretty complex electronics. Just doesn't seem practical to me. A good idea, but not practical.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
If you parallel wired three aircraft landing light bulbs in a series between each glow plug and the wiring harness they would be able to carry the current to heat the glow plugs.
But 24 aircraft landing lights plus the glow plugs are gonna drain the batteries rather quick.
If you fire it up at night, your neighbors will think the sun is up already.
But 24 aircraft landing lights plus the glow plugs are gonna drain the batteries rather quick.
If you fire it up at night, your neighbors will think the sun is up already.
Posting Guru
Joined: Aug 2006
Posts: 2,175
Likes: 0
From: Kent WA
Originally Posted by Dave Sponaugle
If you parallel wired three aircraft landing light bulbs in a series between each glow plug and the wiring harness they would be able to carry the current to heat the glow plugs.
But 24 aircraft landing lights plus the glow plugs are gonna drain the batteries rather quick.
If you fire it up at night, your neighbors will think the sun is up already.
But 24 aircraft landing lights plus the glow plugs are gonna drain the batteries rather quick.
If you fire it up at night, your neighbors will think the sun is up already.
But you're right, it would take some heavy hardware to handle the current....
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
Was I overboard?
I'm sorry.
I was out in the howling wind, 15 degrees, pouring down the snow all day today.
I must have froze to many brain cells, I was trying to be serious and funny.
No sarcasm was intended and no animals were harmed in my reply.
I figure about 200 amps when the glow plugs first start to heat when the temp is about 10 degrees.
So that is about 25 amps per plug.
25 amps at 12 volts is 300 watts.
An aircraft landing light draws 100 watts at 12 volts.
So three of them in parallel will carry 300 watts.
8 glow plugs and three lights per glow plug equals 24 landing lights for indicators.
Only problem is now the glow plugs will draw 400 amps when you start to heat them.
That was the serious part of my post.
The part about the neighbors was the funny part.
I'm sorry.
I was out in the howling wind, 15 degrees, pouring down the snow all day today.
I must have froze to many brain cells, I was trying to be serious and funny.
No sarcasm was intended and no animals were harmed in my reply.
I figure about 200 amps when the glow plugs first start to heat when the temp is about 10 degrees.
So that is about 25 amps per plug.
25 amps at 12 volts is 300 watts.
An aircraft landing light draws 100 watts at 12 volts.
So three of them in parallel will carry 300 watts.
8 glow plugs and three lights per glow plug equals 24 landing lights for indicators.
Only problem is now the glow plugs will draw 400 amps when you start to heat them.
That was the serious part of my post.
The part about the neighbors was the funny part.
Posting Guru
Joined: Aug 2006
Posts: 2,175
Likes: 0
From: Kent WA
Originally Posted by Dave Sponaugle
Was I overboard?
I'm sorry.
I was out in the howling wind, 15 degrees, pouring down the snow all day today.
I must have froze to many brain cells, I was trying to be serious and funny.
No sarcasm was intended and no animals were harmed in my reply.
I'm sorry.
I was out in the howling wind, 15 degrees, pouring down the snow all day today.
I must have froze to many brain cells, I was trying to be serious and funny.
No sarcasm was intended and no animals were harmed in my reply.
Originally Posted by Dave Sponaugle
I figure about 200 amps when the glow plugs first start to heat when the temp is about 10 degrees.
So that is about 25 amps per plug.
25 amps at 12 volts is 300 watts.
An aircraft landing light draws 100 watts at 12 volts.
So three of them in parallel will carry 300 watts.
8 glow plugs and three lights per glow plug equals 24 landing lights for indicators.
Only problem is now the glow plugs will draw 400 amps when you start to heat them.
That was the serious part of my post.
The part about the neighbors was the funny part.
So that is about 25 amps per plug.
25 amps at 12 volts is 300 watts.
An aircraft landing light draws 100 watts at 12 volts.
So three of them in parallel will carry 300 watts.
8 glow plugs and three lights per glow plug equals 24 landing lights for indicators.
Only problem is now the glow plugs will draw 400 amps when you start to heat them.
That was the serious part of my post.
The part about the neighbors was the funny part.
12 volts / 1-2 ohms per GP = 6-12 amps per GP
6-12 amps per GP x 12 volts = 72-144 watts per GP
Or about 1/4 - 1/2 the wattage you came up with.
Either way, the current draw - whether 6, 12, or 25 amps is still too high for a regular indicator light bulb or LED to handle....
Elder User
Joined: Oct 2006
Posts: 597
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Well, you could put a 300A ammeter in series with the relay. That would give you the least
voltage drop. Hopefully you'd have a real good feel for how much draw to expect before any
plugs burned out.
Even better yet, wire up 8 individual ammeters...functional and would really impress the gals.
voltage drop. Hopefully you'd have a real good feel for how much draw to expect before any
plugs burned out.
Even better yet, wire up 8 individual ammeters...functional and would really impress the gals.
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Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 16
From: Nutter Fort, WV
I have to many gauges already.
Mechanical oil pressure
Mechanical coolant temp
Voltmeter
Oil temp
Pyrometer
Boost gauge
All in addition to the stock cluster.
Actually if the battery power and glow plug draw was not so depedant on the air temp,
you can read the voltage drop with a regular voltmeter.
But where it reads at 55 degrees before and after the glow plugs is way different from what it reads at 15 degrees.
Last time I checked my glow plugs it was about 25 degrees, I was reading real close to .5 ohms per plug. That works out to 288 watts and 24 amps per glow plug.
I have also noticed the resistance goes down with the temperature so when it is below zero the draw will be more. But the battery voltage also drops off with temp, so at some point you would reach a max draw ceiling, but I will not speculate on where that is. After the temp goes below zero the last thing on my mind is what the glow plug resistance value is.
If the resistance was .4 ohms at below zero temps, the amps per glow plug would be 30 for 360 watts total.
Mechanical oil pressure
Mechanical coolant temp
Voltmeter
Oil temp
Pyrometer
Boost gauge
All in addition to the stock cluster.
Actually if the battery power and glow plug draw was not so depedant on the air temp,
you can read the voltage drop with a regular voltmeter.
But where it reads at 55 degrees before and after the glow plugs is way different from what it reads at 15 degrees.
Last time I checked my glow plugs it was about 25 degrees, I was reading real close to .5 ohms per plug. That works out to 288 watts and 24 amps per glow plug.
I have also noticed the resistance goes down with the temperature so when it is below zero the draw will be more. But the battery voltage also drops off with temp, so at some point you would reach a max draw ceiling, but I will not speculate on where that is. After the temp goes below zero the last thing on my mind is what the glow plug resistance value is.
If the resistance was .4 ohms at below zero temps, the amps per glow plug would be 30 for 360 watts total.
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