Manual glowplug inquriies ;)

[8v-of-fury]

Hello my good sirs..

I built a glowplug relay setup a la Vince Style, and it works superbly as it should. However I want to intergrade the stock wiring in to what i have got. I want the stock relay and wiring to trigger the relay and sense the coolant temp so it will be left on for however many seconds it needs. I would also like to leave in the manual switch i have on the dash, so that i can trigger the relay for afterglow 30-45 seconds after the car has started.

The Ford Starter relay;


I have the relay grounded to the body, one large gauge wire from the starter post, and the other to distribution block for the gp's. The relay is triggered by a low amperage 18-20awg wire from a switch on the dash to the "S" terminal of the relay. Will the relay work the same way if I were to hook the relay trigger wire up to the "I" terminal?

What I want to do is just take the wire that originally powered the buss bar, and connect it to either the "S" or the "I" of the starter relay. that way the stock system could power the relay or my manual switch could power it depending on the conditions.. Will having the two power sources on the same pole feed power back through the other and cause problems? Will running the manual switch on the "S" terminal and the stock wiring on the "I" terminal work?

ALSO SOME GOOD NEWS, dug the car out of the snowbank it was burried in and it started right up without hesitation... and without the cold start (I have the pump timed to 1.02mm). It was roughly -15 to -20 outside, and 30 seconds of afterglow on the Duraterms reduced smoke after only the first 10 seconds of running.. after that smoke was not visible. Also I did not have to prime the pump with the primer ball in the engine bay.. pump doesn't loose prime.. a very good sign. I have high hopes for this little 900k km engine

What do you guys all think? 

[Vincent Waldon]

IIRC the "I" terminal on the standard Ford relay is how Ford bypasses the Ignition ballast resistor to provide the coil with a bit more oomph during starting... not particularly useful for us glowplug pimpers.  

Having said that, what you're wanting to do is no trouble to hook up.  You could connect both the original glow plug wire and your manual switch to the "s" terminal, but this would allow current to backfeed thru the glow plug relay if the relay and your manual switch are both on at the same time... rogue current paths are not much fun.

The solution is about 99 cents from Radio Shack... two of these puppies:


By using two 1N4001 diodes, Radio Shack part #276-1101 or #276-1102, one in series with the line from the original glow plug relay and one in series with the manual switch, you'll isolate each from the other but can run both at the same time. Note how the diode has a white band marking one end; this is the side that gets connected to the starter solenoid's "S" terminal.

Clear as mud?!!

[8v-of-fury]

So I just have to put one of these resistors inline of each wire? clear as mud

Would the back feeding only occur if both are powered at the same time?

If I only use the manual switch for afterglow and never run them at the same time, will there still be backfeeding through each other?

Thanks a ot Vince Your system works like a CHAMP

[Vincent Waldon]

Yup... although they actually called "diodes"... if you call 'em "resistors" you'll confuse the dude at The Source By Circuit City.  

Yup.

Yup, but the one time you forget and they both are activated at once funny things may happen as the current flows thru strange new paths.  A couple of bucks in parts seems like cheap insurance against a rip in the space-time continuum??!! 

[8v-of-fury]

A couple of bucks in parts seems like cheap insurance against a rip in the space-time continuum??!!

Thanks vince aka Mr. electrical engineer We wouldn't my flux capacitor to act up eh.