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Thread: Overdrive issue

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  1. #1
    Jedi Knight bighealeysource's Avatar
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    Overdrive issue

    Hey y'all,
    Haven't posted for a while, still been reading, just not posting. But of course got a problem. Getting my 100M ready to take to the Atlanta Concours and of course the overdrive goes out as I'm driving along at about 60. Ran fine otherwise and when I got it home did the test where you have the engine off, turn ignition on, switch on OD and then slide gear lever over in 3rd or 4th. Didn't hear the clunk so checked the fuse - have the solenoid wired separately on its own fuse. Fuse has blown. Put another one in, only a 15, try it and it blows immediately. Put the correct 25 in it doesn't blow, but you can hear the solenoid trying to move, like a hum, but no clunking. Thinking the solenoid has failed. Of course if I wasn't getting ready to trailer the old gal up on Thursday, would just take interior apart, take off the tunnel, and see what I have. But, trying to avoid that last minute tear down, etc. Any ideas on a solenoid trying to engage but just humming, not clunking ???
    Thanks
    Mike
    Mike Lewis, 1956 Austin Healey 100M - Registry Confirmed

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    Jedi Knight vette's Avatar
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    Re: Overdrive issue

    Hey Mike, you might have more experience with this OD stuff than me, but I have to say I would not expect to hear a "Clunk" while rocking the shifter from neutral to the 3/4 gate with the engine off. When I do that with mine I just hear the switch on the shifter "clicking" on and off. With the engine off I don't know what piece of the OD that would make a clunk. Also I run my OD (my car is a BJ7) on a 10 Amp fuse. If it is blowing a 15 amp fuse I believe you have an electrical problem. If it is not blowing a 25 amp fuse I believe you still have an electrical problem but it is not dead shorted enough to draw 25 amps. Like I said mine runs below 10 amps. The humming solenoid may be the problem. I've never hear mine hum.
    About TV Shows-
    "...you really can't restore a car in 10 days. I don't want to watch a race where people have to restore it in a week. It's not going to drive, and those cars never work. In real life, it takes years to get it right. " Jay Leno.

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    Jedi Knight bighealeysource's Avatar
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    Re: Overdrive issue

    Thanks Vette ! May be more of a clack than a clunk ! One reason why I am thinking it may be the solenoid is has been running great, OD working perfectly, now all of a sudden it blows a fuse since apparently the solenoid is stuck ( ???) and will not engage. Had some major OD issues a few years ago and became more of an OD expert than I ever wanted to be but just hoping someone comes up with a simple
    answer. Of course, I'll still probably have to get to the solenoid to change it out. Nuts, just when I had it all set to go. One positive thing, don't need the OD to drive onto the show field !!!
    Mike
    Mike Lewis, 1956 Austin Healey 100M - Registry Confirmed

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    Jedi Warrior roscoe's Avatar
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    Re: Overdrive issue

    The solenoid draws a higher current when you initially provide power, then a contact set of points opens and it draws less to keep the solenoid engaged until you turn it off. If you are blowing the fuse it is likley that the points aren't opening as they should and your current draw remains high enough to blow the smaller fuse. My guess is either the plunger in the solenoid is jammed/ broken orn the points are not working/ broken. The click as I call it that you hear when you go left to right in neutral is not the switch, but the solenoid itself engaging and operating the points. It is a pretty beefy electromagnet, not a clunk but a good healthy click. If you hear a hum my guess is that something in the solenoid asembly or the linkage from it to the operating valvemis jammed and you should either not use it or bite the bullet and take a look at it with the cover off. I'd have a new solenoid sitting there if'n I was you.
    Jon Robbins
    1956BN-2 (do it all yourself, you'll be glad you did)

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    Jedi Warrior HEALEYJAG's Avatar
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    Re: Overdrive issue

    Agree....mine has been cutting off intermittently at the same time the fuel gauge and turn signals stop functioning. Can get the overdrive to engage by turning on the turn signals when the switch is flipped.. Now to find that ground......
    1954 Austin Healey 100 Le Mans
    1973 Jaguar E-type OTS
    2015 Jaguar XK Coupe
    2017 Jaguar XF
    2008 Aston Martin Vantage Convt

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    Darth Vader John Turney's Avatar
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    Re: Overdrive issue

    Now that we have "click", "clack" & "clunk", I agree with Jon. I had the same problem with my solenoid a year or so ago.
    John, BN4

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    Jedi Knight bighealeysource's Avatar
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    Re: Overdrive issue

    Hey guys,
    Turned out to be a bad solenoid. Put a new one in and got my "click, clack, clunk" back. Did have to take seats out which is no big deal and avoided taking the tunnel off completely as made enough room to get old one out and new one in. Hoping it was just the old one giving up the ghost and not something else but works good now. Thanks again for the advice.
    Mike
    Mike Lewis, 1956 Austin Healey 100M - Registry Confirmed

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