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Weird Harley starter solenoid issue

Discussion in 'Sensors and Actuators' started by Greasyman, Mar 9, 2020.

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  1. Greasyman


    Mar 8, 2020
    Hi. I have a 1974 Harley Sportster. I broke one of the lugs on the original solenoid, so I replaced the solenoid. The new one wouldn't work, it didn't click or anything, so I took it off to bench test it. I connected it properly to a 12v car battery. The pull in coil worked once and wouldn't work again. The hold in coil seems fine. I checked everything I could think of, tried different jumper wires, etc.

    Finally gave in and bought a different brand for twice the money that seemed identical. Bench tested it before I installed it. Same problem. Pull in worked once and never again, while hold in seems fine. I checked the resistance on both circuits on both solenoids and they are around .5.

    I don't know much about electricity other than it's magic, but this seems really weird to me. Afaik it would be pretty difficult to burn anything out even if I connected the jumper wires wrong, correct? And since the pull in circuit shows .5 ohms of resistance, that indicates that it isn't open, correct? Which means it should work, right? So why doesn't it? Makes me nuts.

    This is the YouTube video showing test procedures that I've been going by. It's less than three minutes long.

    Any help would be greatly appreciated, I have no idea what I'll do next. It's especially bad because this bike has no kick starter.
  2. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sir Greasyman . . . . .

    Two considerations . . . .
    Initially you say . . . .
    The pull in coil worked once and wouldn't work again. The hold in coil seems fine. I checked everything I could think of, tried different jumper wires, etc.

    Now my info is basically with the unit being connected to the Harl l l l l leey and being in real time connected operaation.

    BUT you have the unit ON THE BENCH and have a HEFTY battery ( comsidering that is not a garage floor cast off of the past and now low on charge) for power and a quite decent wattage lamp for a test light / load.

    I would definitively say that the lamp load is borderline on the current capacity of the power capacity capabilities of your " Radio Shack " test leads with clips.
    As you will later read about the POWER consumed in that coil winding within the contacter, I believe that if you made some time of contact between the battery and the coil terminal that the few crimped . . .fine wires of that family of jumper clips . . . have vaporized and open circuited.
    Now, had you been gripping the wire, you would probably have felt the heat build up in the whole wire. It probably has opened up at its weakestt link.
    See if that is the case . . . . . and, if that not being the problem, then . . .there is more . . . .

    Your test shown certainly seems to show that the HIGH CURRENT starter solenoid / contactor assembly is pulling in and passing enough power / current thru its two copperbar contacts inside to light your quite hefty lamp load.
    Now if you look at the specs of that contacters wiring guage and current consumption in fig 5.9 and it being less than 1 ohm for the windings resistance, thats ~12 amps and not what you would want to be running thru your wiring loom and the lighter gauge of wiring that it uses. PLUS . .whats to say that the starter pushbutton switch wouldn't even arc and spot weld its contacts together on initial contact.

    PLIERS PLIERS . . . .QUICK . . . .WHERES SOME PLIERS ! ! ! ! ! !

    SO . . . .there is the starter relay (PINK) of figure 5-10, where , the start button then merely has to pass a meager level of power to the winding of that sttarter relay and then it pulls in its heavy duty contacts, to then provide the heftier power to the winding of the starter solenoid / contactor unit (YELLOW)

    NOW . . . . . in considering that . . . . inspect and test out that starter relay . . . realizing that its contacts . . . . as is being magged up in the 5-10 inset, might have changed in condition from the prime contacts on the right to being the now . . . darkened-oxidized-pitted-erose . . .contacts of the left.
    With it just trying to make contact and probably spitting and making one initial arcing and then a loss of connectivity at a 12 Amp demand.

    Additionally . . . . . resting In the back of my mind . . .any chance that you installed the battery and starter cables transposed to the starter solenoid / contacter unit, with them both being . . . . ALIKE . . . and . . . . BIG . . . . screw + nut terminals . Excepting the longer length of the BATT terminal one .

    Now what say ye . . . about the health of the starter solenoid contacts ?
    ( If you didn't detect a case of burnt open cable-litis back at square #1)



    73's de Edd . . . . .

    I'm really feeling mighty proud of myself today.
    The Sesame Street puzzle I bought said 3-5 years, but I have just now finished it in just under 18 months.

    Last edited: Mar 9, 2020
    Martaine2005 likes this.
  3. Greasyman


    Mar 8, 2020
    Thanks for your help. I tried some of those things but no luck. This is so weird. It reminds me of the time when the six or so cassette decks I owned between my house, garage and cars all failed at the same time. I didn't used to believe in the devil, but now I'm not so sure.
  4. Bluejets


    Oct 5, 2014
    Never heard of a starter solenoid having a pull in and a hold in coil .

    I think you will find the small terminal is supplied power from a start relay whenever you push the start button.
    Return for this would be through the frame bracket normally.

    Then main battery power drives from one of the main large terminals, out through the other, to the motor circuit and then to ground once again.

    As I say, never seen a hold in as well as a pull in coil BUT if present then it would be important to have the starter motor connected to the correct one of the large terminals.

    Above assuming whole control circuit is not negative return switching as some automotive gear may do.
  5. Bluejets


    Oct 5, 2014
    Looked at a couple of videos on 1970 to 1980 Harleys and see they use a system similar to the old Fiat tractors.

    Operation is.....power to the solenoid which pulls in the bendix gear and when engaged, the solenoid main contacts close and direct battery power to the starter motor circuit.

    Just what this after market solenoid is that you have could be questionable.
    Reason being some of the circuits shown have no frame earth return on the solenoid coil but rather get their return through the starter motor itself.
    So where you show a circuit from the small solenoid terminal to the frame, may not be a desirable property.

    73's de Edd circuit diagram above confirms no frame earth return.

    Attached Files:

  6. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Can we get links to both of your replacement units ?
    An can we consider the original broken terminal one to be an OEM Harley unit ?
  7. Bluejets


    Oct 5, 2014
    I suspect the Op's unit is similar to the one below.

    Shows the solenoid operation as I explained in #5 above.

    Perhaps note the video the Op posted comes from a different post by someone from way back in 2013 and may not be a good representation of the Op's gear or problem.

    Reference starts at 14:50.

    Will have to wait for Op's response to verify anything.

  8. Greasyman


    Mar 8, 2020
    Thanks for the responses. The bike is a 1974 Sportster. The solenoids are identical to the one in the video I posted in post #1. All three solenoids appear to be identical to each other. I ran into the guy in the video, "Iron Mike", on a Harley forum, but he couldn't help me. Said he didn't really know that much about electrical stuff. This is where I got my replacements from.
  9. Proton


    Sep 8, 2009
    .5 ohms on each coil, yet only one works means that test method is faulty, relay IS not.

    They offer 2 different solenoids for that ride. If looking at it with the mounting bracket up; The majority are Battery stud is on the right side, starter cable goes onto the left.
    This part is opposite from those (studs are reversed relative to physical mount).
    post #2 figure 5-8 - note longer stud is battery, short stud is ground path thru starter motor for pull in coil (only until motor starts to turn)
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