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Thread: Resistor for Ingition Coil Can't Find?

  1. #1

    Default Resistor for Ingition Coil Can't Find?

    Can't find the bugger on a AQ125A Volvo Penta, any ideas from some one who knows???

  2. #2

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    Not all coils are resistor type. Do you know for sure yours is?

  3. #3

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    wire diagram shows one, but I'm not sure, all original as far as I can tell & since Volvo Penta manual shows one I figured there was one. Maybe I'll buy one and see what it looks like. To last to get it into a shop for M-day weekend. I'll keep trying to trace out wires or jump direct to get power to coil and see what happens.

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    I would guess a resistor for ign would be about inch x inch x 3 inch or the end may be inch round by 3 inch, it will also have two lug one on each side. The reason for an ign resistor is to make a hot spark when starting the engine after the engine is started the resistor is added in series to reduce current so the coil will not burn up. Find your coil and trace the wires back to the resistor if you have one.

    Dose any of this make sense?

  5. #5

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    Not sure of this particular application...but often, a resistor wire is used, as opposed to an actual resistor...Do you have one or two ignition wires running to the primary coil?
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  6. #6

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    I have two wires on the + side of the coil and one on the - side of the coil and wire dia shows that.
    Traced by cutting of the harness jacket and re wrapping it, never found a resister unless it's between the engine and key, normal would be in the engine compartment some place.
    When we ran hot rods we always took the resister out when we raced to increase the spark output so it saves points and coil, but not sure coil cares much?

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    Does one of the wires coming off the + side of the coil have higher resistance than the other? If it does that is a resistance wire or go to a resistor.

  8. #8

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    Well new coil with built in resistor , new condenser and bingo sparl at the points, turned over ran for 3 min and stopped, no spark again, tryed 12v batt to dist no spark. Well not looking good for M-day weekend

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    Ok. you have put 12v to the + side of the coil. With the - wire disconnected you should have voltage at the -side. No voltage means coil is bad. If you have voltage there, hook the -back up and hand turn motor over until points are closed making sure that the points are opening and closing. Now with a piece of plastic or wood push the points open and let them close. It should spark at the coil each time you do this. If not, check the voltage at the - side of the coil with the points closed. If voltage is 12, you have cooked the points. This will happen if you have a coil that needs a resistor and doesn't have one. Unless your coil says in writing on it that it does not need a resistor, someone may have sold you a coil that does in fact need a resistor. Another check you can make is to turn the motor till the points are open and check voltage on the - side of the coil. It should be between 8 and 12 volts depending on resistor or not. If voltage is correct, touch a screwdriver blade between the two parts of the points. It should spark at the coil. If it does but won't spark when cranking it usually means the points are burnt.

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    Keep in mind that some ign. coils are internaly resisted and they are marked as such. If you have a 12v test light, attach the clip/wire to a good ground and hold the probe end against the neg-. terminal of the coil, crank the engine and look for a flashing test light, if it flashes then the coil and points are working. Also pull the rotor and check to see that there is a not burn through the rotor to the dist. shaft allowing the spark to go to ground. If you have a DVOM be sure to use it to set dwell of the points correctly... measuring the gap is best used when there is no other choice.

  11. #11

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    Well I did most of those test, I have replaced every part except the key switch, ohm reading on the wires from the switch back seem wierd, so next it's start replacing wire and take out the connector plug harness. Fiddled with it and got power to the points bingo fire at the coil and she started right up. So when to Whittier did fine Sat then Sun after noon it just stopped, no spark at points. so has to be wire. soon I'll have a new system but good old salt water and electrical connections is my guess now. Never found a resistor and not sure how a resistor in coil would work if both wires are on the same point. Start curcuit starts with 12v to the points, run curcuit is thru resistor to lower voltage hence saves points. Maybe pulling that wire out I'll find one. Resistor impedence wire ? if I end up with 12 v to the points I'll change points ever 4 trips or something, nice hot spark!

  12. #12
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    Pull that dang points thing out and upgrade.....my 2 cents, but may solve some of the headaches. I put a Mallory in one of my old boats and never had to go back at the ignition again.

    As a matter of fact, seen the old girl at Freddie's a couple weeks ago. It's the only one I have ever seen in the state so pretty easy to spot. It's a Larson DC International. The engine and outdrive have been completely changed out thru the last owner. The overall condition of the boat was back to the way that I had purchased it. The current owner, purchased from the person I had sold it to. Got a good deal, but she needed alot of TLC again. She looks like she sat under some trees uncovered for a couple of years. The wood was almost so dry that it may need to be replaced.

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    I'm thinking you probably have a wiring problem between the ign switch and the coil. If it were mine, I would run a new wire from the ign switch to the coil and put a resistor from an old chevy ( 1955/1970) in line. Check the two wires going to the coil + with the key on. One should have voltage the other should have none. Check the one with no voltage when cranking and it should show 12v. If it shows no voltage, it's broken somewhere between the coil and the starter solinoid and needs fixed. If it shows 12v reattach it and the new wire and you should be good to go. If nothing else I would carry a spare resistor, points, condenser, rotor,coil and a length of wire and you can get spark just about no matter what. If you go to an all electronic set up, you need to get spare pick up coil, ign coil, control box and any other electronic components that help make spark cause when they quit parts replacement is your only option. With a points set up, usually a new set of points or clean the old ones and you can get home.

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    My boat was a charter boat. Previous owner put a new engine in it and ran a season of charters with no problems. On my second trip out the engine stopped and I trolled back to port with the kicker (caught my first salt water king on that troll). Problem later proved to be a burned out distributor. I bought a new Mallory and the enclosed instructions said to install a resistor. I am by no means a mechanic, all of this boating maintenance is new to me, but I am a DIY er and I tend to make do with what I have laying around. I bought the resistor, made a little bracket with a piece of aluminum angle and I was back to fishing. Last summer the coil went bad. The parts man at NAPA on 6th ave E was very knowledgeable about boat electronics and he said this is a common problem with my set up and the reason is not known. I carry a spare resistor and coil now.
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    Fishnngrinn:

    There may be a couple of reasons the resistor is burning out, the wrong size resistance (they sell one value for all Coils). That looked like a 50 Watt resistor, the wattage needed is determine by it location, mounting it on top of the engine is not where it should be put (the engine gets very hot). If you relocated to the fire wall it will be a lot cooler and last longer, or you could go to a larger size (wattage). The first thing I would do is make sure it the correct resistance.

  16. #16

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    Well yup thats what they look like but still can't find one. But when running a ohm check on the two wire that come from the ignitin key, same length, right next to each other. One would by pass the resistor to start it, when you let go of the key into the run position it then does thru resistor to cut down the voltage and save points. Yupper thats what happens. Anyway both wire had different ohm reading and when I added power had diff voltage reading, resistor ? still none in sight. Bad connection all corroded up could do the same, plugg the connector plug and yup all gunked up, so one wire at a time I'm hard wiring together. At least the last thing I replace or rewire will be the problem child and I'll have a new system.

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    try crowley marine online, Any volvo dealer should have a resistor in stock

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