GP Controller CV & MV Differences

[Stihl029]

I have a few questions about the differences in the glow plug controller for a CV and a MV.

1. Besides 24VDC (MV) and 12VDC (CV) what are the differences?

2. Is this something that maybe one with some soldering skills might be able to alter?

3. If the CV model is a physically different size or shape would it not still be possible to re-enginer it to accept 24VDC? I have spotted a few CV versions around my local parts yard.

4. Does any one have the scematics for both circuits? I do not and I just toasted my ironkey with all my tms on it, I think I have a backup at work.

Not saying I have a problem, as I have a manual bypass right now that works fine, thanks Matt. I just believe that the system was designed to work automatically and therfore it should. Mine had some corrosion and jacked components which I plan on replacing as soon as I can find my card again lost it and my ipod last friday so it might be in my other jeep that a shipmate is borrowing. I have no problem swapping components and adding jumpers if that's all. I have seen the GP controller card pop up on here frequent enough that I am suprised that there is not a sticky for it other than a sole source for procurement and several schematics to set up a bypass/manual and 12VDC conversion.

From how I understand the system it work like this:
1 turn key to run
2 thermostatic sensor senses temperature:
a) if engine is correct temp procede to step 4
b) if engine temp is no correct to create combustion procede to 3
3 control card energizes GP relay (pwr comes from the resistors), passes to the GP's in a parrellel circuit.
4 once block is up to temp the thermostatic switch changes state, wait light goes out
5 crank engine over

I know that this is the down and dirty. This is my first MV (I have helped work on a M715 and a M38 in the past) and my first diesel. My Dad had a few f-250's not gassers and learned to drive stick in a 97' so I have been around them just never really had to work on them. I do have a fair amount of mechanical skills as is evedident by my Cherokee(only thing stock is the unibody, doors, the engine and the steering pump and box); but I just want to really feel that I understand something before I go balls deep into it. I am not interested in modifying it unless it is something that I cannot get ahold of, I understand the preservation of these rigs.

Andy

 

[doghead]

Schematics for both GP systems are available here on the site. Look at the Tech articles and the TM sections.

 

[kennyw]

Only major difference is the resistor bank.

 

[dependable]

Many of the civ 6.2s are set up for 12v input and 6v output for the 6v'' fast glow'' plugs. I went to manual glow switch and 12v plugs on them before I ever owned a cucv.

 

[kennyw]

Many of the civ 6.2s are set up for 12v input and 6v output for the 6v'' fast glow'' plugs. I went to manual glow switch and 12v plugs on them before I ever owned a cucv.

GM just put 12V to the 6V glow plugs. There is no means of dropping the voltage from 12V to 6V. This makes a 6V glow plug heat up fast, but also burns them out faster and in many cases swell. If one dies you still have a 12V supply to all the plugs since everything is wired in parallel.

On the military system the resistor bank is wired in series and drops the voltage from 24V down to 12V while they run 12V plugs. However, if one dies, the total resistance changes (glow plugs are part of the total resistance in series with the resistor) and that raises the voltage in the circuit. This speeds up the death of the next plug which raises the voltage again. The more glow plugs that burn out, the higher the voltage and the faster the rest of the plugs start to die.

 

[dependable]

Not sure I agree with you kennyw, 12v fries 6 v plugs almost instantly. There was a resitant circuit in the round civ glow control, diameter of a quarter, about 2 or 3 inches long mounted on rear of driver side head. When these cive controls failed, they put out 12v instead of 6v, and fried the plugs. This resulted in the early demise of many civ 6.2s. due to broken plugs in the cylinders. If you are getting 12 v out of the control on the civ head, then it has already failed.

 

[kennyw]

All of my civi 6.2's have been 12V at the glow plugs (12V hooked to a meter only, more like 10.5V with the voltage drop from the glow plug load). But they have all been the older style controllers (82-84). I don't burn up glow plugs.

I found this link:
GM-GMC: 6.2 diesel, ac delco, glow plugs

It says the 60G's are rated at 10.5V.