GPR switch and pilot light issues

[steve604]

i decided to wire up a switch to shut off my glow plugs and install a pilot light in the dash for them.

i wired the switch in series with the red wire that connects to a small terminal on the GPR. i wired the pilot light directly off of the load side big terminal of the GPR. i have a big stancor relay in the truck and everything seemed to work ok before doing this aside from the fact that the truck had a hard time cold starting at below 4* celcius (40*F?). sometimes it has a hard time cold starting at 15* celsius so i wanted to install this stuff to see what it was actually doing.

the pilot lamps i used aren't led so there is no neg. terminal, basically just a straight resistor. i've burned up two of these now and i actually had the wire burn the insulation off on the second one i tried (i know i should have had it fused). i also tried using an on off switch with pilot light for this so i could turn this light off. i wired it with a ground wire exactly where it's supposed to be on the switch and that burned up.

the switch i wired up seems to turn the glow plug relay off and on ok. the switches i used are the cole hersee rocker style that also have a pilot light so i decided that it wouldn't hurt to hook that up (neg to terminal 4). that pilot light on the switch would also light up everytime the glow plug relay trigger wire was live which would be able to tell me if the trigger wiring is working ok.

the problem i'm having is that everything i install here is burning up aside from the switch i installed for the relay shut off.

i checked and tested the switches and lights before installing them the second time and everything has been 12 volt rated and the pilot lamps are all about 35 ohms which works out to be .34 amps draw.

is it possible that my engine block isn't grounded well enough to handle the current of the glow plugs? are my pilot lamps attempting to partially complete the circuit of the glow plugs? is this why my glow plugs all seem to resistance test ok at the valve cover plugs yet probably don't perform properly due to bad grounding? i looked for engine grounding straps in a few places and can't find any... if it's not a gas engine with spark plugs does ford not put in ground straps because they're "not needed"?

it all seems so simple.....


my original plan was to use this switch so i could also manually turn my GPR on if i wanted to and it would have two pilot lights

[NoRalPh]

I'm having trouble following you here, not sure what you need the switch to do. If you interrupt the power side of the coil (sm terminals) you're still giving the PCM the final control. Is that what you want? You want to override the PCM's control and be able to Not use them sometimes, but they still will Only come on with the PCMs direction.

If you want Total control of the GP system your sw should be on the Ground side of the circuit so the sw supplies the path a ground. That way they are on/off anytime you want.

Next the bulb, why not simply run a hot wire from the Load side to the light (I soldered a 1A fuse inline and covered it with HeatShrink at the relay).

If your block wasn't grounded, your Starter wouldn't be able to work, you should see a battery cable going to the block itself.

[steve604]

for beginners, i can't seem to get a pilot light to work off of the big load terminal of the GPR. the pilot lights keep burning up for some reason and i can't figure out why it draws so much current. i am going to try a fused LED tomorrow.

the switch to interupt power to the control side of the GPR seems to work ok but i'm not sure if it's drawing a massive amount of current though so i am going to fuse that one too.

i also wanted to be able to manually turn the glow plug relay on also but i'm starting to think that is pointless anyway.

[Macon]

If you wired the light in like you did on that diagram, then that is why they are burning up. They will always burn up. When the relay opens, the light becomes the new path of travel. You are sending a couple hundred amps through your dash (twice) as the GP's try to stay on. Go from post 4 to gnd for your light. Post 4 being GP supply line, as I don't know the number on a Stancor.

[NoRalPh]

Originally Posted by steve604

for beginners, i can't seem to get a pilot light to work off of the big load terminal of the GPR. the pilot lights keep burning up for some reason and i can't figure out why it draws so much current. i am going to try a fused LED tomorrow.

If you wire the bulb, in series with the Load, it becomes a fuse (I'm not sure I see that in your diagram though) are you Sure it's a 12v bulb?
The same thing is going to apply to an LED but, be aware, because they are NOT 12v devices, you'll need a resistor when wired properly (from the Load side to Ground).

Originally Posted by steve604

the switch to interupt power to the control side of the GPR seems to work ok but i'm not sure if it's drawing a massive amount of current though so i am going to fuse that one too.

As I said before,,,, that's not the way to do it. The GPs are NOT controlled by applying 12v (that wire has 12v in it the Entire time the key is On), the PCM controls them by applying GROUND. So, your way, if the PCM wasn't supplying that ground, because it didn't want them On, you can't make them come on. BUT, if you supply Ground though the sw, you would have total control. Also, that wire wouldn't require any kind of fuse (that circuit draws Very Little anyway)

Originally Posted by steve604

i also wanted to be able to manually turn the glow plug relay on also but i'm starting to think that is pointless anyway.

Do you need to override the PCM or is the PCM not turning them on when it should?

[Macon]

Originally Posted by NoRalPh

If you wire the bulb, in series with the Load, it becomes a fuse (I'm not sure I see that in your diagram though) are you Sure it's a 12v bulb?
The same thing is going to apply to an LED but, be aware, because they are NOT 12v devices, you'll need a resistor when wired properly (from the Load side to Ground).

You may be right about that. I don't know the actual pin out of the GPR, but what he explained the drawing makes me go with that thought. The only thing I can figure is the light is becoming the path to supply the GP's, which will blow it, and if it's strong enough, will melt wires before that happens. I would hate to see the wires melt the shielding then make contact with each other and start a fire.

I found this topic to help him out on the light part (which is what I got the pins from on the last post)

GPR LED mod

That should fix that issue, which seems to be the main problem, as the switch is switching for him. An spdp switch will be needed for manual vs PCM control. One position to PCM, the other to ground, center pin to GPR gnd.

I'll draw up what I mean right quick.

(Pins marked as per the link)

[steve604]

that is exactly how i wired mine. i took no wires off of the relay aside from a small red one so i could interupt control power to the relay during the summer so the glow plugs aren't coming on unnecessarily. i added a wire to the big terminal that is not always live to feed my pilot light on the dash.

i am going to have to look at it again later on. i must be doing something stupid that i can't see.

[steve604]

i played with it a bit today and it seems to work fine now. i connected an LED to the big terminal load side of the relay and it worked fine. i used a switch without pilot light for control wiring of the relay so i can turn the glow plugs off if i want.

i think what i did wrong was i connected the pilot light to ground on the switch which caused funny stuff to happen. i think the PCM might power the glow plug relay independently (internal transformer?) of the truck's electrical system which could cause more that 12 volts to ground..... not going to try that again.

i think i am going to try to find one of these switches Rocker Switches | Weather-resistant Rocker Switches | LED Pilot Lights | SPST On-Off Rocker Switches, one pilot, independent illumination58312-R2 | Cole Hersee - Littelfuse

wired like this without the jumper. the pilot light will be independant of the control circuit for the relay.

[NoRalPh]

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