Ballast Resistor-Question??

[Mr. Jones]

On my 66-350,64 style cab with factory installed 300/240 engine and wiring harness,I'm needing to figure out where this might be located,a mechanic thought it could be the problem causing my erratic spark out of the coil.Billy(the mechanic guy) said to look for a porcelain block in line with the coil???I've had this truck almost 30 years and have never seen anything similar.Perhaps it goes by a different name or design.Anyone know what he's talking about???
Thanks,
Dan

[64 f100]

Ballast resistor was replaced by a resistor wire under the dash. Usually can be spotted by the cloth covering placed dover it. There is a wire coming off the ignition switch that it connects to, sorry I don't remember the color , and then plugs back into the harness going out the firewall. When you turn on the ignition, you should have 8 volts or less at the hot wire on the coil. You can disconnect the positive wire going to the coil and check the voltage there. The coil can be checked with an oscilloscope. However, if it has been overheating from getting to much voltage it may be damaged internally causing erratic spark. What information did the mechanic base his statement on? After rereading your statement, it sounds like you only asked for advice and did not actually take the truck to this mechanic. Erratic running on the sixes can be any number of things. What I do know is that Ford sixes had carb problems and on occasion the heat riser flapper comes loose in the exhaust manifold and will mess with the engine. Did this just suddenly start happening, or has it gone on for along time? Was this truck driven on a regular basis or does it set a lot of the time? I know you only asked about the resistor, but there are several really good mechanics on here that can point you in the right direction. These trucks have a particular set of problems that many on this forum have dealt with.

Rich

[Mr. Jones]

64,
Hope this helps,the erratic spark came from grounding the coil wire to the block and using the ignition switch.With the wire 1/2"-3/4" from block the spark is a strong red, seemed to stay that way for a few moments then vanish.Move the wire closer nothing,kept cranking and it would reappear.
The problem began two years ago,occasionally I had it back on the road after a distributor replacement,good for month.Had it running a month ago,drove it till everything reached operating temp.Set the timing,drove some more engine had power,carb was responsive,thought I had it solved.Next day,nothing, seemed to be firing on two cylinders.
As for Billy,he's not actually looked at it.We spoke by phone yesterday,a friend of a friend.Seem knowledgeable of electrical systems.
I will inspect the resistor wire after it warms up.Thanks for defining that thing..I will measure voltage at coil too.
Thanks,
Dan

[ThinLizzy13]

The resistor wire is pink

[banjopicker66]

Your mechanic friend doesn't know Fords of the '60s and '70s very well.
As Rich pointed, out, Ford didn't use a ceramic block style like the other manufacturers did, but used a long resistor wire, pink and wrapped with pink cloth with green ends. It is wrapped up in the under-dash wiring harness.

Usually, it did not plug directly into the ignition switch, but was fed off of a pigtail off the ignition switch.
If your truck runs, then I doubt the resistor wire is failing. It either works or doesn't.

[ThinLizzy13]

Sorry I don't have a better pic, but the block in the top left is what he's talking about. The PO of my truck installed one. The reisitor wire was still in my truck. The two combined made my truck so some funky things.

[ICEMAN6166]

this is the correct part for our trucks


http://ecatalog.smpcorp.com/STD/#/vehic ... -34?type=s

i have seen a few slicks with these
theres one on the rambler. old dodges had them too
if you have one on a slick its likely the correct wire has been replaced with non r wire so the ceramic resistor is used.




never should you have both and if you have a ceramic the resistance must be the same as the original wire

[Mr. Jones]

Banjo,
Good point,works or doesn't,now I'm really confused.I'm at that,"Now what'll I do"point.
Guess I'll finish installing shocks on the 250,went with Monroe's gas on the front coil-overs on the rear.Maybe someone will have an idea which way to go with the 350...
THANKS again,
Dan

[banjopicker66]

If you are running points, I would suspect first a failing condenser in the distributor and then a failing coil.

[Mr. Jones]

Found the resistor wire,pig tail off ignition,pink.Followed it across and lost it above the pedal assembly,don't know where it terminates...

[Mr. Jones]

Banjo,
Condenser shows a barely persecptical arc,was told a large blue arc meant the condenser was bad??Coil was replaced when the timing was set a month ago..

[ThinLizzy13]

The resistor wire on my truck goes into the connector on the fire wall

[banjopicker66]

Found the resistor wire,pig tail off ignition,pink.Followed it across and lost it above the pedal assembly,don't know where it terminates...

The actual wire stops at the bulkhead connector.
The electrical path continues through the bulkhead connector to the coil.

[64 f100]

When was the last time you checked the points? How much play in the distributer shaft. Bad condenser will cause backfiring as general rule. I disagree with ice on the resistor wire. These can loose resistance and allow full voltage to the coil causing the it to overheat and break down. I would tend to think more in terms of bad connection in the system with intermittent connectivity. Old wiring don't you know. Just remember a multimeter is your friend. I would check the resistor wire to see if it is braking down. A month may have been long enough to ruin that new coil.
Banjo, Ford used the external ceramic resistor in earlier years. Not certain when they went to the wire type, but I know my 57 retractable had a ceramic resistor.

Rich

[64 litl un]

Who knows whats been done, you have to figure that out. It would bug the hell out of me not knowing. You have to trace those circuits back to the switch. Per factory no block is needed other than the resistor wire for the ignition /switch hot. BUT who know what the PO did.....heck he may have other stuff tied into the block like all the gauges......The only way is to trace wires and see what was done and try to figure out why.

[Mr. Jones]

Guys....this is where I'm at.Removed the firewall junction block and found a lot of corrosion on the male and female connections.Cleaned them with emery paper,it was difficult to get inside the female(no jokes please)thoroughly.Any way it didn't work.
This morning I pulled a resistor wire from an old harness,only to find this written on it "Resistor wire do not cut or splice"that's some tech bs IMO.My plan is to bypass the the junction block and go straight to the dist.wire and see what happens.Anyone ever do this?
Dan