Glow Plug Resistor

[donalloy1]

Dear Fellow SSer's,

Changed out Glow Plugs today because I have been having poor cold starts. All Plugs looked ok and came out without any problems.

Put Meter on Glow Plug while Son cycled ignition till Wait Light came on. Measured 8 vlts dc initially and increased to 10 vlts dc and then voltage went to zero after a few seconds. At that time I noticed some smoke coming off Glow Plug Resistor assembly? She started right up without hesitation on first try. Nice and warm out this afternoon!

Apparently my GP Resistor is done or getting ready to die. What do I do now? Hoping somebody knows a source for the GP Resistor Assy. Want to keep her OEM as possible. Will go another route if need be.

Look forward to your valuable technical suggestions as always. DMLII sends...

 

[Warthog]

Used is the only option I know of. So many guys are removing theirs and going to 12v you should be able to find a few to buy.

 

[cpf240]

Were the glow plugs working before? If not, it could just be dust and dirt burning off the resistor. You know, like when you turn on the heater in your house for the first time when the cold season starts.

You could also just do the 12v bypass and eliminate the resistor. When I did the bypass on mine, I also had to replace the glow plug relay. I'm guessing it was due to the contacts being coated with a layer of carbon.

 

[donalloy1]

Used is the only option I know of. So many guys are removing theirs and going to 12v you should be able to find a few to buy.

Thanks for response Warthog! Anybody in paticular you could steer me to for used GP Resistor?

If I must go without. Is there a reccomended process that I can adhere to?

 

[Sharecropper]

Like many on this site, I bypassed my GP resistor to circumvent cascading failure. There are numerous threads on here which will explain why this is a must-do modification.

 

[Matt65]

Mine was bypassed. It never did anything but cause a cascade failure of most of my glow plugs. It serves no purpose that I can think of beyond cold starts with totally dead batteries on the slave.

 

[donalloy1]

Were the glow plugs working before? If not, it could just be dust and dirt burning off the resistor. You know, like when you turn on the heater in your house for the first time when the cold season starts.

You could also just do the 12v bypass and eliminate the resistor. When I did the bypass on mine, I also had to replace the glow plug relay. I'm guessing it was due to the contacts being coated with a layer of carbon.

cpf240, all was good until last week. Do not understand what could have caused this condition? Man against machine I suppose. Sooner or later we lose! Probably just plain tired?

Its burning off dust alright! Will try again later when it really cools down tonight and watch with Flashlight. Sit Rep inbound after that observation.

What is best way to bypass?

 

[Matt65]

For what it's worth, I know where another one is laying that was working when removed. Let me know of you want it.

 

[ARYankee]

I would recommend the glow plug resistor bypass. Read some of the stickys as well because they are extremely helpful.

 

[wayne pick]

Don, in your climate, your truck should start just fine after doing a risistor bypass.

 

[Keith_J]

The resistor gets as hot as the glow plugs. They will smoke if any dirt or bugs get on them. It doesn't mean the resistor is burning out.

Cascade failure happens when the glow plug card fails in the on state. The card should prevent glow plug cascade failure.

 

[cpf240]

What is best way to bypass?

Here is one thread you might find interesting: http://www.steelsoldiers.com/cucv/56682-what-why-did-smoke.html

Post 18 shows one popular method. The other is to go directly to the 12v buss right next to the glow plug relay.

Part of the problem with the resistor setup is that as each glow plug fails, the voltage seen by the other glow plugs goes up. Yes, the glow plug controller card does monitor the voltage going to the glow plugs, and shortens the cycle time to compensate for a higher than spec voltage.

To my mind this means the glow plugs are not being allowed to work as they should, and this may shorten their life span. IE getting zapped with a higher than spec voltage over and over again.

Opinions go both ways on this one, and I was more comfortable running them with the bypass and not worrying about over voltage conditions.

The other often mentioned downside to the 12v bypass is that the glow plug system won't get the 24v supplied to it when using the NATO slave port. Some have done the 12v bypass but left the 24v wiring accessible to switch back if needed. I would think that letting the batteries charge for a bit from the donor vehicle via the slave port would be enough to allow the glow plugs to cycle and get the vehicle started.

I only have the one vehicle with a slave port, and so don't consider the jumping issue to be high on my list of concerns.

YMMV

 

[MarcusOReallyus]

H
Opinions go both ways on this one, and I was more comfortable running them with the bypass and not worrying about over voltage conditions.

This is a no-brainer. While I understand the reasons for the original design, it's still a bad design, just begging for problems.

 

[donalloy1]

Figured I would go out this morning and Cold Start again. The overnight conditions went into low 50's. Had Daughter go through start up procedure while I observed GP Resistor. No smoke? Started right up on first cycle of Glow Plugs

Maybe cpf240 is right out of shoot on this Thread?

Bug or Dirt cooking off Resistor?
New Glow Plugs caused more heat at Resistor?
Owner to critical of vehicle?

What I will do for now is monitor Cold Starting performances. If she blows she goes. Meanwhile study up on bypass pros/cons vs. replacing with used unit. Still really not totally sold on bypass if I can get my hands on a serviceable resistor.

Really appreciate all the words of wisdom. DMLII sends respectfully

 

[SouthernSteel]

I would have thought the 12volt conversion would be basically the same thing just with out all the problems of the 24 volt resistor.I took my resistor off today and used the wire with the fusible link in it to use as my jumper from the 12 volt block right above the Gp relay to the relay itself and im going to go get AC 60's as i had a ac 13 g go bad it was split right in two mind you these are about 2 year old.

 

[m38inmaine]

I'm not jumping on the bypass wagon. By bypassing to 12v you are doubling the current drawn on the 12v supply wire and I'm not sure it's rated for that. You are also pulling a large amount of current from the front battery which will over time weaken it. Regular glow plug maintainance will prevent multiple glow plug failures. In cold weather the original sytem is a real bonus as you are only drawing half the current and saving battery power for cranking.

 

[tbearatkin]

I'm not jumping on the bypass wagon. By bypassing to 12v you are doubling the current drawn on the 12v supply wire and I'm not sure it's rated for that. You are also pulling a large amount of current from the front battery which will over time weaken it. Regular glow plug maintainance will prevent multiple glow plug failures. In cold weather the original sytem is a real bonus as you are only drawing half the current and saving battery power for cranking.

I have the same batteries since I started the post on what is it and why did it smoke in Aug of 2010. Batteries are still strong. Many have used the 12v Supply wire on the firewall with no problems but I as well was concerned about the current draw so wired it directly to the battery. I did have to replace the brand new relay as it seemed the 24volts through affected how it worked when it only got 12volts. Mine I think was still good just had lots dust and dirt on it from never really have to heat up to reduce it down to 12volts as all the GP were burnt up. Glad I bypassed it and the only issue I had was when getting the IP rebuilt the mechanic hooked it up to 24 volts and burnt them all out. My fault for not labeling the wire 12Volts only.

 

[SouthernSteel]

Im actually thinking of doing away with the glow plug card and the sensors all together but for now im going 12 volts persay technically it was already 12 volts so really you are doing away with a problem.I have heard and seen to many thing happen with the resistors my uncle worked onthe cucvs while he was in the army even he said to bypass it.I wouldnt be surprised if warthog,doghead,waynepicker or some of the others dont jump in and agree with me.Though its your truck do what you want. I personally know the resistors are prone to going bad and they drain the batteries at some point and may even catch fire due to the age and the trash and dirt that get on them.

 

[Keith_J]

The function of the resistor is more complex than just voltage division. The glow plugs have resistance which has a positive temperature coefficient, the resistor has a neutral. With the control card, the system offers faster pre-glow warmup in very cold conditions.

The resistor is around 0.50 Ohms, the glow plugs in parallel are around 0.20 Ohms. The glow plugs get an initial voltage of over 17 volts when cold. Once they warm up, the voltage drops to about 11 when the resistance in the glow plugs increases.

 

[wayne pick]

Im actually thinking of doing away with the glow plug card and the sensors all together but for now im going 12 volts persay technically it was already 12 volts so really you are doing away with a problem.I have heard and seen to many thing happen with the resistors my uncle worked onthe cucvs while he was in the army even he said to bypass it.I wouldnt be surprised if warthog,doghead,waynepicker or some of the others dont jump in and agree with me.Though its your truck do what you want. I personally know the resistors are prone to going bad and they drain the batteries at some point and may even catch fire due to the age and the trash and dirt that get on them.

When my GP controller card sizzled shortly after getting my truck, I went with a manual GP switch, removed the resistor and fed the GP solinoid with 12v from the negitive side of the rear battery as per instructions for this conversion. I used a #4 battery cable, more than enough to feed the GP solinoid. The PO installed a spin on fuel filter, so I have no air infiltration issues, and all my glowplugs work perfectly. Even in my cold winter climate, I have no starting issues with this truck.