Glowplugs Never Energize and Have You Ever What the Inside of a PCB Looks Like

[70deuce]

When starting my 1985 M998 the wait light would flash for a second and go out. Impossible to start when cold. It has a KDS protective control box dated I think Oct of 2010. Figured that was the culprit so I removed it, opened it up and Houston we have a problem. Look at what is called a MOSFET (definition to follow) closest to the 24volt solenoid. See anything wrong? The box has that funky fried smell to it also. Little surface corrosion on connections that I don’t think caused the problem. MOSFETs are cheap and readily available and I have 5 of this part coming. This thing is listed to be rated at 55V and 74A. Pretty significant specs. I just am going to replace the fried one and clean up the connections and see what happens. I know it’s better to go the the ESS box but for $3 and a little time what the ****. I will update the post when the parts arrive and the box is back in and tested. I never did any service on the start system i.e. disconnect a cannon plug without disconnecting the batteries it just stopped working. OK here is the definition of MOSFET courtesy of Wikipedia. Enjoy this one! The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET). It has an insulated gate, whose voltage determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. A metal–insulator–semiconductor field-effect transistor or MISFET is a term almost synonymous with MOSFET. Another synonym is IGFET for insulated-gate field-effect transistor. The main advantage of a MOSFET is that it requires almost no input current to control the load current, when compared with bipolar transistors. In an "enhancement mode" MOSFET, voltage applied to the gate terminal increases the conductivity of the device. In "depletion mode" transistors, voltage applied at the gate reduces the conductivity[SUP].[/SUP]

 

[orgnal]

Nice write up! Keep us posted! I hope you get it to work!

McReddy

 

[ken]

Sounds like someone may have a new side business.

 

[FloridaAKM]

Replacing the MOSFET should be a straight forward process because of its physical size. Making sure that nothing before it let out the magic smoke may be a problem. Keep us posted on your progress & how it all shakes out. Good luck with your project!

 

[1 Patriot-of-many]

I have a box that fried the same mosfet. I also have some, never got around to replacing it. Let us know how it turns out.

 

[papakb]

If you want to build in a little higher rated MOSFET you could use these : P75NF75 STP75NF75 TO-220 MOSFET N-Ch 75 Volt 80 Amp. Just search this string to find them.

One other problem I've noticed in designs using MOSFETs is that designers tend to rely on the internal diode to provide backswing protection in circuits and those internal diodes aren't all that healthy. Parallelling the output with a better diode will help keep the FET alive. Schottky Barrier Rectifier Diode 60V 5A SR560 ESUS

 

[70deuce]

Addressing FloridAKM's thought of what let out the magic smoke in the first place ever other sensor and part of the glow plug seems to check out OK. New MOSFET not coming in for awhile Thanks also papakb for the advise on a higher rated unit. I probably will search one of those out and try that one. More to follow.

 

[jeffy777]

It looks like to me there maybe an issue with the CAMDEC Solenoid. The power lead from the bus looks scorched a little also. I would replace that as well. Just my two cents.

 

[Awol]

I had something similar happen to my 94 F350. I took the computer apart, and was greeted with a similar sight. I replaced the little guy, and was back on the road.


Amazing such a little thing can cause a giant problem.

 

[86humv]

Here's some photo's...
First is an old LAU.....not used anymore.
PN 12379864

# 2..KDS green label...CR-2699.....burnt and corroded.
This old type can use any temp sensor or none.

 

[86humv]

This one...KDS yellow label 12469158-1
Can use KDS or Nartron temp sensor 12469158-2


# 2 is a Nartron yellow ...12469158-1....burnt up.
Uses temp sensor 12469158-2 also

 

[86humv]

KDS Smart S3....socn6500435, cr-2700
Uses KDS or Nartron temp sensor 12469158-2


Nartron Smart S3...socn12480779
Uses Nartron 12480779 temp sensor, and maybe KDS or Nartron temp sensor 12469158-2

 

[86humv]

KDS Silver label...1246779....uses temp sensor ...12338772 grey or black top.
Can't use KDS or Nartron temp sensor 12469158-2

Then there's these 3: SSI yellow label 12469158-1 uses Kds or Nartron temp sensor 12469158-2.
Its riveted together...not screws like the others on upper posts.
The Prestolite and Ametek are 12446779 and riveted also......these two use the Nartron
temp sensor 12338772 only.

 

[86humv]

Temp sensors....

 

[86humv]

Nartron Temp sensor 12480779, use with Nartron S3

 

[70deuce]

Installed the new MOSFET. Did not fix the problem. Good news though. It forced me to do something I wanted to do anyways. I bypassed the PCB control of the glows plugs completely. I will never have to worry about that box again for control of the glow plugs. The box feeds an 8 gauge wire from the the circuit board to the engine connector above the PCB box. That wire from the box feeds circuit 575 that comes out of the PCB engine connector in the engine bay through the "D" pin. In the pictures I mislabeled the circuit number. It is not 571 it is indeed 575. 571 is the "wait to start" light circuit. I disconnected that wire in the PCB and connected it to a new insulated through the box terminal that connects to a 24V continuous duty aircraft relay that came from an surplus OH-58 Kiowa (Bell Jet Ranger) helicopter. I will connect the relay to a push button switch that will be mounted in a existing hole the military drilled in the dash. I have used a jumper wire to test the new circuit out and it works great! Energizes the glow plugs only when the relay is energized. I now have complete manual control of the glow plugs. Pin "E" on the body connector is the hot feed to the "wait to start" light. I will tap into that circuit so anytime I push my new glow plug switch that light will come on. 45 degrees out today, energized the glow plugs for 6 seconds and she fired right up. Tapped a constant 24 volts for the hot power side of the relay from the battery box battery + side terminal connection on the side of the batter. 8 gauge wire used for this connection. I added a picture of the lighter socket I use for my Solargizer connection. I just unplug it when I drive it. Allows me to place the solar array in the best place to face the sun no matter what direction the vehicle is pointed while parked.

 

[DCIV]

So how much would you charge to make this a plug and play kit? I would love to have this for when mine eventually goes.

 

[frank8003]

Installed the new MOSFET. Did not fix the problem. Good news though. It forced me to do something I wanted to do anyways. I bypassed the PCB control of the glows plugs completely. I will never have to worry about that box again for control of the glow plugs. ~ to a 24V continuous duty aircraft relay that came from an surplus OH-58 Kiowa (Bell Jet Ranger) helicopter. ~
and it works great! Energizes the glow plugs only when the relay is energized. I now have complete manual control of the glow plugs. ~ 45 degrees out today, energized the glow plugs for 6 seconds and she fired right up. ~Solargizer connection. I just unplug it when I drive it. Allows me to place the solar array in the best place to face the sun no matter what direction the vehicle is pointed while parked.

This is in the Sticky category.
I was going to put the Thanks note on your post on your work and proof but this gets a big fat good ATTABOY! This is really neat, thanks.

 

[70deuce]

Installed the push button switch and labelled it. Just need to find the hot wire to the "wait" light and wire it in so it comes on anytime when this button is pushed.

 

[doghead]

What if it gets ground to activate it?