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Fuse Box & Electrical Gremlins

Discussion in '1965-1970 Shelby Mustang GT350 & GT500' started by shelby68gt500, Aug 24, 2007.

  1. shelby68gt500

    shelby68gt500 Well-Known Member

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    Working thru the customary electrical gremlins now that I'm able to fire up the motor again. Everything seems to operate as it should (nothing electrical is smoking), but still have the following issue:

    When attaching the positive battery cable, I'm getting a nice little arc and the accompanying snap & crackle. I put my ammeter inline and it shows something miniscule like .002A. If I let the car sit connected for more than a day or so, the battery will be dead. Tried to isolate this by pulling fuses one at a time, but even with all fuses pulled it still does it. I've attached a pic (hopefully) of my fuse box with the fuse values listed. Not sure if they are correct as I can't really read the lettering on the fuse box itself and the books I have aren't real clear.
    Also, when attaching the positive battery cable, I hear a faint gurgling type of noise for just a few seconds (even with all fuses pulled). Thought this might have something to do with the heater (valve opening or closing when power applied as it seems to come from behind the firewall), but believed that nothing should happen with all the fuses pulled. Now thinking that possibly the clock (inoperative) and the stereo memory lead will be my next check, but these still don't explain the gurgling sound.
    Hoping that some other folks may have run across this previously, I'm scratching my head....
    [​IMG]
    Thanks, Bob
     
  2. The Commissioner

    The Commissioner Well-Known Member

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    Can't help you out, but suggest taking it to a reputable electrics shop for a complete check up. Chased electrical gremlins for several years on my 67 GT350, with original wiring/fuse panel etc and just finally gave up. Took it to an electrical shop, and they were so happy to work on a car like this, they roped it off in their shop and the head electrics guy spent 2 full days checking every single wire and connection he could get to, and man did he do a good job, in the past 4 years, not one problem. Amazing how many issues bad grounds, a crusty contact can cause with original wiring. They charged me a whopping $300 for the complete job, about 12-14 hours, of which I was expecting to pay triple. Sometimes you can find a gem of a shop by looking for the "small business guy". When we do our M3 GT350 Replicas, I just go for the entire Painless system, it's not cheap, but worth it in the long run if you're not worried about originality.
     
  3. shelby68gt500

    shelby68gt500 Well-Known Member

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    Commish,

    Thanks for the input... Virtually the whole harness is brand new... I'm starting to look at the specific wiring to see if I can pinpoint some swapped wires or something. If I can't find anything this weekend, I'll probably do as you mentioned... as I really have so little time to work on this car with 5 & 7 year olds and a job that is relentless with the hours... The motor is finally right with it, now this electrical issue... Wondering if it will ever end... But, I LOVE this car so much, I don't ever see getting rid of it. Guess it is one of those tough love situations! Bob
     
  4. DJames

    DJames Member

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    The tiny bit of draw you registered on your ammeter sounds like what one would expect the radio to draw to remember the pre-set stations. That isn't nearly enough to kill the battery in a couple of days, assuming that the battery is good and that your charging system is operating correctly. For something to be killing the battery with the key in the 'off' position, it would have to be a problem with something that has constant power, not keyed power. That makes for a pretty short list of suspects. On your car,if it's basically 'as original', the only things drawing constant power, or things that work whether the key is on or off, would be your horns and your lighting (headlights, parking lights, courtesy lights,etc).Try disconnecting the constant power wire for the radio, which is probably hooked to the hot side of the starter solenoid, and then take a volt meter and put the positive probe on a convenient place on the body of the car where it's making good contact and put the negative probe on the negative battery post with the key off and the doors closed. If you still have a draw, unplug the turn signal switch pigtail, which has the horn button wiring in it, and check again with the volt meter for the draw. If it goes away you either need a new turn signsl switch or need to replace the wire that goes from that connector to the horns. If it doesn't go away the problem is going to be somewhere in the lighting wiring. That one you have to sort of start at one end of the system and go through until you find the problem. It is frequently the headlight switch, but, it could be anywhere. Good luck.
     
  5. shelby68gt500

    shelby68gt500 Well-Known Member

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    DJ, Thanks for your response... That was kinda my thought as well. Radio & clock (even though it doesn't work) would be the only things I would expect to draw anything with the key off and doors closed.... I've replaced the headlight switch already, so hopefully I can exclude that. I am having an issue with the turn signal switch though, you may be onto something there. Anytime I turn the wheel about to 10 or 2 o'clock and back, the turn signal switch clicks even though I hadn't thrown it. It does operate normally otherwise the last time I checked it.
    There is definately something upstream of the fusebox drawing most if not all the power. The only thing I notice when I put the cable on (other than the arcing), is the slight gurgling sound that appears to come from around the firewall, but I can't be sure. It only lasts about 3 seconds though, so it is hard to trace. Got to be something related to the heater/core, but how if the key is off?

    Bob
     
  6. DJames

    DJames Member

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    The only thing electrical in the entire heating system is the fan motor, which is supposed to be keyed power, but after 40 years of "I don't care. Just fix it!" ( never say that to a mechanic) you can never be sure until you check. The heater core itself doesn't have any wires going to it, so it is definitely not reacting to the battery cable being re-attached. The clicking thing with the turn signals is just the plastic cancel cams sticking in a little too far. It's probably annoying, but it isn't going to cause any problems. I think that the first thing that I would do is disconnect that turn signal switch and then check to see if I still had the draw with a volt meter. Keep in mind that car batteries produce hydrogen gas and that they are vented. A simple equation to remember is spark+hydrogen= hindenburg. You might want to keep that sparking the positive post thing to a minimum.:D Also, try unplugging the wires from both horns before you reconnect the battery and see if that gurgling thing still happens. BTW, do both horns work? Also, what motivated you to replace the headlight switch?
     
  7. shelby68gt500

    shelby68gt500 Well-Known Member

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    DJ, Horns have not been reinstalled yet, have been waiting to workout the bugs with getting the motor back in before putting all the finishing stuff back on. I had replaced the headlight switch a couple of years ago (it was original) as I had a very scary experience with another 68 Mustang years ago when in the middle of a night drive, my headlights decided to cut off. Talk about testing the adrenaline gland... Turned out that the switch had corroded over time and as the contact heated up, continutity was lost. I always keep a spare switch nowadays just in case. My thought on the gurgling was that there was a valve or something supplying coolant to the heater core that opens/closes causing the gurgling, but still that should be keyed versus always powered. Maybe you are right about something in that circuit being modified previously. I've yet to find anyone online or local that has been able to pin down that gurgling-type of noise, it really is a odd issue.

    Bob
     
  8. shelby68gt500

    shelby68gt500 Well-Known Member

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    DJ, Another couple of things that just came to me... My car is a factory 4sp with factory Air. I'm now wondering if that gurgling sound could be something related to vacuum. I've got a couple of vacuum canisters that have been replaced within the last couple of years, but currently, they aren't even connected into the system. The compressor is out of the car and the lines are still there, but not connected either.

    Bob
     
  9. DJames

    DJames Member

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    Sounds pretty promising so far. So, the lighting in he car you have now wasn't malfunctioning, you merely replaced the switch as a precaution. If the horns are on a shelf somewhere they probably aren't the problem. If all of the lighting seems to be working like it's supposed to that puts you back at the turn signal switch for the power draw, assuming that it isn't something like the glove box light staying on all of the time. I really don't know what to tell you about the funny noise. Without being able to actually hear it, all I can do is mention some things that it isn't. If it happens with the engine dead cold when you reconnect the battery, it isn't anything related to the cooling system, like the heater core. If everything electrical in the car seems to be working then it isn't anything that has to do with starting system, like the solenoid or the starter itself. The only vacuum-related system that works with the key off is the kick-away steering wheel and that isn't something that would make a funny noise that lasts for a several seconds, and if the car hasn't been running there isn't any vacuum to generate funny noises anyway. I would pretty much have to see the car to dial it in any closer than that. Could you stuff it through the monitor so I can have a look at it?:)
     
  10. 65gtfastback

    65gtfastback Well-Known Member

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    Last time I had a similar problem it turned out to be a off brand voltage regulator, ..the big one on the radiator support. Its easy to swap out to see. Good luck. I would not leave your car alone with battery hooked up until you sort it out.
     
  11. 67GT500#2100

    67GT500#2100 Shelby Forums Pit Crew

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    I had a friend have a similar problem and it turned out that since he was a nonsmoker he used his ashtray as a coin holder. Well, somehow a penny fell into the cigarette lighter power point and killed his battery. He was lucky that the thing did not burn up. He had removed the cigarette lighter to power up his phone and left it out. Any way it is worth checking since this is one area that gets power without having to have the key on.
     
  12. DeLa1Rob

    DeLa1Rob Well-Known Member

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    I had the penny in the cigar lighter problem in my Masi. That really did cause a mess of problems.

    You may want to also verify that your battery does not have a short. Check the cells with a hydrometer. On my car, if I fired it up every day it was fine. If it sat a day or two, the battery would be dead. The battery was new so I looked elsewhere for problems. I fixed every possible source of a drain I could find, but still the problem persisted. Finally, I thought back to basics, and used a hydrometer to check the battery. Two of the cells were basically pure water. Amazing that it would even take a charge. I replaced the battery and have had no problems since.

    robin
     
  13. shelby68gt500

    shelby68gt500 Well-Known Member

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    Thanks Gents for all the ideas... I've had another person comment about the VReg, I might just get another unit to test with and keep it for a spare if it doesn't change the outcome. That sound just confuses the hell out of me... I will certainly post when I finally figure out what is causing it...

    Bob
     
  14. wcampbell

    wcampbell Active Member

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    Bob,

    Call *** ******** up at The Muscle Car Shop (***-***-****). He's about 15 -30 minutes drive from most of Northern Virgina so he's close to you. He turns out some beautiful SHelby restorations and does piece work. He'll have you back on the road in no time and knows these cars like the back of his hand. Tell him Wayne Campbell sent you. Good luck.

    Wayne
     
    Last edited by a moderator: Jan 26, 2010

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