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Missing coil resistor, wiring advice requested


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I'd had trouble starting my 521, and there appeared to be both ignition and fuel related problems. Finally had some time to spend with it yesterday, and though we got it started (yay!), I'd like some advice for wiring in the coil resistor that's currently missing. 

 

The truck has a single points distributor. Points replaced recently, condenser and coil replaced yesterday, and it started right up. I think the condenser was the primary ignition related problem. Other factor to note: PO wired in a push button ignition.

 

So, I'm assuming it would be best for me to get a resistor in place. (Will the lack of a resistor continually burn out the condenser and/or points?) And the resistor should be in between the positive coil terminal and ignition according to the Haynes manual. Currently there are two connections to the positive side of the coil, and I don't know where they end up. I'd like to avoid undoing the whole loom to find out. I'm hoping someone with wiring knowledge can give me some hints.

 

I'm also open to other options. I do hope to put an electronic dizzy in someday...

 

Coil wires (Black/Red was cut/re-connected):

1C93C3C5-BA3D-48E1-AB1C-4111B50C2EB0_zps

 

My best attempt at diagramming the situation at the coil and at ignition. Both the Black/White and Black/Red wires connected to the positive on the coil disappear into the loom. According to Haynes, the BW is the one that goes to the resistor.

 

C34B31E0-693F-4F60-890E-250978C6DAF1_zps

 

Connector box under dash/ignition wires

30CF5476-EA86-4BDB-945D-23C4AB925073_zps

 

This is what my fuse box looks like in case anyone's curious and wants a good laugh.

 

B27D9A63-3813-4BE9-B4F3-3BF7761CAEE1_zps

 

Thanks in advance for any guidance!

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The coil and the points cannot sustain a full 12 volts. The coil will heat up and possibly fry. The points will arc excessively and burn out in 50 -150 miles of driving. It won't hurt the capacitor. 

 

The ballast resistor drops the voltage to about 8 volts in the On or run position of the ignition switch. The Start position sends 12 volts around the ballast resistor for more spark during engine cranking and when the key is released it reverts back the the 8 volts from the ballast.

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You must use a ballast resistor with a ballast resistor coil.   It limits the current throught the points, so they last longer, and lilits current throught the coil, so it does not overheat.

 

The free end of the black with red wire goes to the ballast resistor.  This wire goes back through the wire harness, to the ignition switch, and is hot in the crank position.

The black with white connects to the other end of the ballast resistor,  This wire goes to the fuse box, and is jumped to a black with white wire, that goes to the ignition switch.  Iis hot in run, and crank position.

 

Here is a 521 wiring diagram.

521wires.jpg

 

 

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Thanks DatzenMike and DanielC! So I can undo the connection on the BR and put the resistor in the middle. I'll see if I can find the BW leading into the fuse box. I'm still not sure how everything intersects at the ignition, so I'll need to dig deeper there.

 

I know I need a resistor (and I'm not too cheap to buy one). The PO took it out and must have carried a carton of extra points with him at all times.

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He may have had an EI set up he took with him.

 

Make sure you get the correct resistor. It will have to have a high wattage to dissipate the heat it makes. The stock ones are ceramic and get way hot enough to burn you.

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"I'm still not sure how everything intersects at the ignition, so I'll need to dig deeper there."

 

Do not overthink this.  it is easy.  On second thought, I looked at the picture of your fuse box.

 

This is a description of stock 521 ignition wiring.

There is a white wire from the positive battery terminal to the fusebox.  It connects to the engine side of the fusebox.  Three or four fuses are always hot.  There is a second white wire, that goes into the wiring harness.  This wire goes to the ignition switch, througth some connectors.

A black with a white stripe wire comes fron the ignition switch.  It also goes to the engine side of the fuse box, and when the ignition switch is on, supplies power to the fuses that are NOT always hot.  There is a second black with a white stripe wire also connected to the engine side of the fuse box.  This wire goes to the ballast resistor, then that current goes into the blcak with a red stripe wire, and to coil positive.   The ballast resistor, and coil are in series.  the coil negativce is grounded, sometimes by the points.

When the key is in the crank position, the black wire witha red stripe is connected by the key switch to the main white wire, suppling power to the ignition switch.  This wire goes directly to the coil, bypassing the ballast resistor.

 

I live in West Linn, and would be willing to help you, if needed.

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He may have had an EI set up he took with him.

 

Make sure you get the correct resistor. It will have to have a high wattage to dissipate the heat it makes. The stock ones are ceramic and get way hot enough to burn you.

I've only seen ceramic ones around, and was planning on going with this, or similar: http://www.rockauto.com/catalog/moreinfo.php?pk=50065&cc=1209956&jnid=399&jpid=2

 

If you have other suggestions, I'd be curious.

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An update: got the resistor in and wired up. I was overthinking that part -- Hainz was correct. I did also confirm that a BW is going into the fuse box on the engine side as DanielC described (I'm assuming the fuse box melted at some point, explaining all the red wires that were spliced on to make connections from the originals).

So, one more mystery (at least to me) is this:

  • With the key in the on position and the resistor connected, the volts coming from the coil read at around 8-8.5. Great!
  • But, out of curiosity, I also tested the volts coming out of the coil with the wires back in their original position, sans resistor -- it read the same 8 - 8.5. Weird, right?!
  • Finally, I tested the volts from the coil with resistor connected when the truck was running, and the output ranged from 3-5 volts. It bounced around a lot, but never went higher than 5.

Does this sound normal to others? Perhaps my assumptions were wrong...

 

What I was expecting was:

  • coil, with resistor, in "on" = 8v
  • coil, no resistor, in "on" = 12v
  • coil, resistor, running = variable, but high of 8v

The coil is definitely a "use external resistor" type coil.

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This is the circuit path for the ignition circuit on a stock 521. Battery positive, to hot side of fuse box.  A white wire goes to the ignition switch, and is not fused.  When the ignition switch is on, a black wire with a white stripe goes to the ignition switched fuses.  There is a second black wire with a white stripe wire that goes to the ballast resistor.  The other side of the ballast resistor  has a black witha red stripe wire, that goes to coil positive.  Coil negative goes to the points, and the points ground the coil, and then the engine head connects the grounded distributor back to the battery negative.

 

If the points are open, you should measure battery voltage at at either end of the ballast resistor, or even coil positive, or coil negative.

if the points are closed, the 8 or so volts between the ballast resistor and coil are normal.

If the engine is running, you are actually measureing the average of the voltage with the points being closed, and open, as the engine runs.  These voltages will also be influenced by inductive kickback, everytime the points open.  In this case, you are actually measuring an alternating current, that only stays positive, and a DC voltmeter may not measure it accurately.

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