can anyone tell me where the ignition coil ballast resistor is located on a 1985 F-350 (460 7.5)???

 

If carburetor, it is in the harness between the box on the fender and the coil. If fuel injected it is in the harness between the coil and ECU.

 

Book doesn't call it a ballast resistor, but a resistor wire which references to the coil. The wire is 49" in length, red with green stripes. No pic could be found.


D7AZ-12250-A Resistor (Motorcraft DY 213)

 

its normally easy to tell which wire is the resistor. its feels different, a little heavier. check the wires between the ignition box and the coil

 

probally a stupid question, but would that wire being bad cause me to have no spark out of the coil? i already replaced the coil, ignition module, distributor and cap/rotor and still no spark!

 

Dunno...did you replace the pickup coil in the dizzy? The usual routine when changing modules (at least in a dealers shop) is replacing both.

 

I Replaced The Whole Distributor...new Pick Up Coil And All.

 

Usually it is comes out of the ignition switch.

For years it was Pink in colour.

 

what comes out of the ignition switch?

 

Dennis! Voila!! doggone it...I couldn't remember where that dang wire went.

THX

Maybe the red with green stripes resembles pink more than red...I kinda think that's right.

 

how do i know which ignition system i have? duraspark II or III? do i have a c.p. sensor? also "numberdummy/mil1ion" the resistor wire comes from the ignition switch on the column to the coil?

 

If you have a DuraSpark ignition, the primary cause for distributer failure is the connector between the reluctor and the DursSpark ignition box. On V8's the connector normally winds up lying on the inake manifold and arc's to ground at that point. Check all your connections from the distributor to the ignition module!

 

According to the digrams...

Circut 16: Red/Green Stripe wire hot in run only from the ignition switch, goes to splice-401, where three wires and the resistor split off. The resistor and two of the wires will be Red/Green Stripe, the other will be Light Green/Red stripe.

The resistor wire will be marked, do not cut or splice.


The other end of the resistor is at splice-216 there will be two wires, one Red/Green wire that goes to the coil, and the other is Brown/Pink, which is the start bypass that bypasses the resistor in start only.


The splices should be obvious, they are usually big black or gray rubber colored that resembles a barrel. Should find it under the dash.

You can test the resistor with a multimeter set to ohms. The resistor should resist voltage 1.05 to 1.15 ohms. If it is more than that or not at all, replace the wire etc...


Yes the resistor being bad can cause a no spark condition. But only when the truck ignition is in the run position. If the resistor was the only culprit of no spark, the truck should start up and then die.

This is because of the resistor bypass when the coil gets its full 12 volts from the ignition switch in the start position. In the run position the coil only gets around 7 volts.

Hope this helps...

 

i checked for power at the coil with a test light and both terminals on the end of the coil have power. is that right?

 

Look at and in the distributor itself.

Duraspark II distributors will have a "cog wheel" inside with 8 teeth. And you will see the magnetic pickup assymbly, will also have wires going to it. Ignition Module is located on the fender, and is independant of any computer control. Will also have a vacuum advance on the side. Most common before 1984.

Duraspark III distributors, they have no guts. They are just a rotor inside and some alignment screws. No wires going to the distributor at all. No vacuum advance. Ignition Module is located on the fender, and is dependant on the EEC-III computer system for control. Also has the CP sensor. Most comon on V8s in california before 1984.

TFI-IV distributors, the rectangular ignition module is located directly on the outside and bolted to the distributor. Dependant on the EEC-IV computer for control. Most common on trucks 1984 and up.

hope this helps...