serious glowplug re rigging help needed

[thorn]

this is almost more for an electrician than a mechanic, and a stretch but im at a loss here.
ill look for diesel forums as well.

ok = 6.9L Ford (international motor).

the glowplug controller dies way too rapidly, got sick of replacing it.
was heating plugs by jumping relay instead, circumventing controller.
wires seem to have corroded, that stopped working, so was doing direct wires form plugs to battery, but this is buring up plugs like mad.

i guess easiest would be rewire and go back to jumping relay , BUT
here is the bigger issue=
truck is obvioulsy 12 volts, stupid glowplugs are 6V. controller supposedly dealt with this by flickering the power to keep plugs alive longer.

can i get a resistor that can handle the amperage and rewire myself?
(ps yes, this means everytime i start, i hold wires connected to heat u prather than turn key and wait to start)

any suggestions at all? at this point i almsot want to rip out the plugs entirely and put a freggin toaster heat element in there.

[Azrael256]

You can get a resistor to do it, but it's going to have to be a big one.  One of those nice big ceramic jobbies would do the trick.  I would not, however, advise it.  It's going to get awfully hot in a real hurry.

Check all the circuitry between the glow plugs and the switch.  You probably have a short somewhere.  Or a bad ground.  I don't know just why a bad ground would burn up the controller, but it always seems to be a bad ground everytime something on my car goes nutzo.  You should find complete schematics in the Haynes or Chilton guide, which is available anywhere.  If you can get the actual shop manual from Ford, that would be even better.

[thorn]

only the mitchell guides have wiring, maybe there are basics in chiltons.
(mitchells are huge, expensive, but in the library)

for some reason the controller is Notoriously bad on this model, possibly from the fact it is mounted directly into the water? seems to me it should have had a seperate temp sensor. oh well.

hmm a huge ceramic resistor, but you say it'll get hot?
i mean i only need it for ten seconds first start in the morning, rest of the day truck will start off its own heat.
if it was a tighter newer engine, i should be able to start without plugs in summer, but its too old.

maybe the electronics store will have it. anyway point is, short or no short, i intend to replace all the wires, but the controller ($120) will always fail. previous owner told me it died every 3-4 years!! and others have told me it is a year/engine specific problem.

[Azrael256]

Yeah, the chilton's just have schematics.  They don't have really good wiring diagrams, and no explanation whatsoever of what the harness looks like.

Another though occurs to me...  I used to use regular voltage regulators for stuff like this.  Any idea what the actual amperage is on the plugs?  A 7806 would give you a good +6, and it'll eat up to something like 30V before burning out, so running it off 12V is no biggie, but you're only going to get about 1A.  If you need more current, an LM350 is more like it.  I've seen them run up to ~10A, but you're going to need to do some soldering.  If it's more than that, I can peruse the National catalog, but I've never built anything to run that hot.

The main problem with using a resistor is size.  If you get one of the wirewound resistors, not only is it inductive, but one the size of your thumb is only going to be rated for 10-15W.  Being just a long wire, it's basically a toaster element.  A ceramic (usually called "non-inductive") of the same size will handle twice the wattage, but it's going to get kinda toasty.  Even for ten seconds, it's going to get hot if there's a high load.

What you really need to know before you build anything is what the current draw is on those plugs.  You can't tune the system to deliver the voltage you want without that information.  Also, if you can come up with that data, and just a little bit more, we can probably design a new module from scratch that doesn't require electrical burns and exploding ignition systems.

Btw, you said notorious...  are we talking a 1986?

[yesterdaysyouth]

if the plugs are rated for 6 volts then why not wire two in series??

[larry_minn]

Get 12 volt plugs.  As said short term wire in series.  (Nope can't do it)  The positive is on top (wire) the negative is where it goes into block (kinda like a spark plug)  So not practicle to wire in series.  It has been years but my 1984 6.9 got 12 v glow plugs.

[cfabe]

get 12 volt plugs sounds like the best solution. A linear regulator would work as well as the resistor method, but I imagine glow plugs will draw alot of current, so you're going to have to get rid of alot of heat either way. You'll be generating as much waste heat as all the glow plugs are generating.

[thorn]

wow guys thanks- i been away from the site a minute- ok it is an 83- seems like ~ 81-86 are very much the same trucks.

now i cnat even figure for sure the plugs really are not 12V or what.

i need to figure out what the heck they draw and how.
another forum was suggesting something similar to the series idea- that if you run less than 8 plugs, those then get more juice.

so maybe if i run all 8 positives down into one wire? (the block is neg)

i hear you guys on the resistor genreating the heat, seems like that wont work.

for now i am starting on one plug at a time -a real hassle, but i was buring out several in the same amount of time.

i think really what was happening is the wires are so shot, even when i had 8 good plugs, only 5-6 get current, and too much.
hopefully ill get to replace all of them and all wires next week

[yesterdaysyouth]

if you run all the pos wires together you will put them in parallel...  expect smoke then flames...