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Thread: Death by Electrocution

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    Death by Electrocution

    Hello all,
    This is my first post to this site, but Iíve had various old British cars over the years, and have been generally able to deal with the various fixes and problems that arise with them. Of course thatís much of the enjoyment of having them. However British electrics have not been one of my favorites in that area. With that said, of course that is what has stricken my 61 TR3a. The car has been restored within the past year by a friend in the local British car club who does a very nice restoration overall. The car looks and runs excellently until a day ago, while out on perhaps its last run before winter. (of course). It happened while motoring along, all going well, when a sudden small spark and pop from behind the dash happened and the engine died, the gen light on the dash came on and after pulling over to the side of the road, no power to anything. I quickly popped the hood and disconnected the battery. No sign of anything under the hood, and on examining behind the dash as best I could all I could see only two small white wires hanging down, but nothing else. After towing it home, and looking at a wiring diagram, it appeared these white wires were from the push starter switch and going to the ignition switch nd then to the gen dash light and to the fuse box on one side, and to then to the coil. I reattached those as per the diagram and still nothing. The only power I can find is at the starter solenoid at these top terminal with the brown wires out. No power at the bottom output to the red/white wire, which goes to the starter push switch. Thatís kind of it so far. Donít know if it could be the control box, the solenoid, the lighting switch (I had just turned on the lights a few minutes prior to the electrical excitement) Any ideas and help would be greatly appreciated.

    Rob
    TRrover

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    Re: Death by Electrocution

    Quote Originally Posted by TRrover View Post
    Hello all,
    This is my first post to this site, but Iíve had various old British cars over the years, and have been generally able to deal with the various fixes and problems that arise with them. Of course thatís much of the enjoyment of having them. However British electrics have not been one of my favorites in that area. With that said, of course that is what has stricken my 61 TR3a. The car has been restored within the past year by a friend in the local British car club who does a very nice restoration overall. The car looks and runs excellently until a day ago, while out on perhaps its last run before winter. (of course). It happened while motoring along, all going well, when a sudden small spark and pop from behind the dash happened and the engine died, the gen light on the dash came on and after pulling over to the side of the road, no power to anything. I quickly popped the hood and disconnected the battery. No sign of anything under the hood, and on examining behind the dash as best I could all I could see only two small white wires hanging down, but nothing else. After towing it home, and looking at a wiring diagram, it appeared these white wires were from the push starter switch and going to the ignition switch nd then to the gen dash light and to the fuse box on one side, and to then to the coil. I reattached those as per the diagram and still nothing. The only power I can find is at the starter solenoid at these top terminal with the brown wires out. No power at the bottom output to the red/white wire, which goes to the starter push switch. Thatís kind of it so far. Donít know if it could be the control box, the solenoid, the lighting switch (I had just turned on the lights a few minutes prior to the electrical excitement) Any ideas and help would be greatly appreciated.

    Rob
    TRrover
    I feel for you. I had a similar problem that was caused by the bonnet (hood) prop rod touching the wiper motor, grounding out everything!
    Sounds like you can read a schematic and have a voltmeter. Are both fuses and the fusible link intact? Pop off the control box: Underneath on the bottom side are more fusible links (flat wires). Iíve burned one of those. Mustíve been a short somewhere. Do you need the schematic? Jim

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    Re: Death by Electrocution

    Quote Originally Posted by TRrover View Post
    ...all I could see only two small white wires hanging down, but nothing else. After towing it home, and looking at a wiring diagram, it appeared these white wires were from the push starter switch and going to the ignition switch nd then to the gen dash light and to the fuse box on one side, and to then to the coil. I reattached those as per the diagram
    That sounds right.

    Quote Originally Posted by TRrover View Post
    ...The only power I can find is at the starter solenoid at these top terminal with the brown wires out. No power at the bottom output to the red/white wire, which goes to the starter push switch...
    That sounds normal.

    Since things are coming loose back there - the one set of connections that would kill everything should one of them disconnect are the leads to the ammeter. These are thick wires, one Brown and one Brown/White. Could be something else but that is a place to start.

    You should disconnect the ground post of the battery before you go poking around back there.

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    Re: Death by Electrocution

    I agree the ammeter is a possibility, but I hate working under the dash. So I would start with some checks under the hood/bonnet first. Both A and A1 at the control box should have power all the time. If both are dead, check at A1 on the fuse block (two brown wires). Power at the brown wires, but not at A (NW wire) would point at the ammeter or the wires and connections leading to it.
    If A is hot but A1 next to it is not, then the control box has failed inside. Not common, but it happened to me.

    If A1 on the control box has power, then you'll have to move under the dash. The NU wire should carry power from A1 to the headlight switch, then on to the ignition switch.

    BTW, the RW wire is an input to the solenoid, it should be hot only when the ignition is on and the starter button on the dash is being held down. You should be looking at the path
    Battery->solenoid->N wire->fuse block->N->ammeter->NW->control box->NU->headlight->ignition->W->fuse block (again)->coil. IIRC this part is the same, but the diagram in the workshop manual (reproduced in many places as being for all TR2/3) does have some significant differences in other areas; particularly the wiper motor and rear lamps.

    Although it does require more care, I would leave the battery connected and some device turned on (like maybe the wipers) while doing circuit checks with a voltmeter. Otherwise, you can be fooled by connections that can pass enough power to run the voltmeter but not enough to run anything else. For example, a 10k ohm resistor looks like a piece of wire to a DMM, but an open circuit to anything on a TR3.

    PS, Welcome to the asylum! Not to worry, there are no stupid questions here (tho we do occasionally come up with some stupid answers )
    Last edited by TR3driver; 11-28-2017 at 01:46 AM.

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    Re: Death by Electrocution

    With ign sw off, run a hot wire from battery to coil. Hit the starter button and see if it starts. That will give you idea of wiring harness condition. If it cranks then I would look at ign sw first and trace down the white colored wires to see if there are any burnt or melted wires.
    Marv

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    Re: Death by Electrocution

    Just to add to the ammeter- if you had a short, and pulled too much current through the ammeter it can unfortunately act like a fuse and blow out. I'd go with Randall's check of the brown-white wire at the A1 terminal of the controller - if it is dead and the wires don't look loose behind there you may have a fried ammeter.
    Randy
    70 TR6 - running
    59 TR3A - slumbering
    64 TR4 - got another one!

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    Re: Death by Electrocution

    Pumpkin and Yoda,
    well its looking more and more like its the ammeter as there is power only through the Brown wire to the ammeter and all terminals at the control box are dead. Sooooo if its the ammeter, i see that they no longer exist at the usual suspect parts site, so is there a suitable replacement somewhere? The series of events leading to the failure point to too much stuff on like heater fan, headlights, dash lights etc, but still don't know why this led to the death of the ammeter. Perhaps it was weak and old to begin with, and the resistance in the circuits and contacts. your thoughts?
    Rob

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    Re: Death by Electrocution

    My ammeter also shows no reading. I've put in a new loom. I'll check A1 on the controller. The temp gauge works but not the fuel gauge, I haven't connected the gauge voltage regulator yet.
    The ammeter shouldn't be affected by the regulator. I have an earth wire attached to the ammeter gauge holding screw. If I attach an voltmeter across the brown wires at the back of the gauge and I get a reading then I assume that I've managed to blow the gauge. I hope not. Aside from that the car starts and runs well.

    Jim and the 1962 TR4 slowly coming back together.
    Last edited by jimstr4; 11-28-2017 at 02:14 PM. Reason: Syntax error

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    Re: Death by Electrocution

    Rob, unless you have a short or have added some high power device, I seriously doubt the ammeter failed due to overload. Internally, it is just a small coil of fairly heavy wire. So I would say it was a combination of old age and normal load that did it in.

    I assume you've checked right at the terminals of the ammeter, to be certain it isn't a bad connection or broken wire. I would check again once you've got it out of the dash, just to be sure.

    They aren't a common failure item, so a used one is probably your best bet; or else send yours out for repair. Lots of places will restore them, cost is probably around $100 or so. North Hollywood Speedo is one in the LA area, I can't think of the others offhand. Lots of other places across the country, including MoMa in New Mexico (IIRC) and Nisongers on the east coast.

    Almost any aftermarket 2" gauge will fit and work, but they usually look way out of place.

    Another option might be to open it up yourself. Like I said, it's just a loop of wire (the needle responds to the magnetic field) so it's easy to repair. Probably the trickiest part is just bending the tabs back and forth without breaking them and even a broken tab or two won't keep it from working.

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    Re: Death by Electrocution

    Rob,
    One option is to switch to a voltmeter. I run one that was sold by Harbor Freight in my TR4. It does have the flat glass rather than domed but it does not look to out of place. To be able to use it you need to take the two ammeter wires and "wire"them together.
    But I would bet that you can find a used ammeter either here or on eBay. If you find a flat glass one you should be able to remove the front chrome ring and switch your domed glass onto the new unit.
    Charley
    Charley
    1962 TR4
    1963 TR4
    1959 TR3A A work in progress.

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    Re: Death by Electrocution

    Another update. Well after finding the ammeter shot(no continuity from terminal to terminal and the brown I was hot, but the brown/white wire to the control box was dead.) we put in a new ammeter and continuity was good between the two terminals of the ammeter and between the brown/white wire from ammeter to control box, but still no power to ignition, lights etc. I then looked on the underside of the control box, where there are fused links and saw the fusible link on A terminal (which is from the Brown/white lead from the ammeter) was blown! So I’m assuming that link was exposed to a power surge when the ammeter blew. I’ve ordered a new control box. Thoughts?
    Rob
    TRrover

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    Great Pumpkin TR3driver's Avatar
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    Re: Death by Electrocution

    I'm not even convinced those conductors are intended as fusible links; let alone that they could be blown by such a trivial surge. I used to run a 60 amp alternator, along with high power stereo, electric radiator fan and 100watt halogen headlights. Had to add a shunt to the ammeter because it was hitting the peg after every cold start (and starting to damage the mechanism). I ran that configuration for many years before one of the connections inside the control box finally let go.

    So IMO either it was coincidence; or you had a massive short somewhere else.
    Randall
    56 TR3 TS13571L daily driver
    71 Stag LE1473L waiting engine rebuild
    71 Stag LE2013LBW waiting gearbox rebuild

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    Re: Death by Electrocution

    I disconnected both wires from the generator. The voltage between the large connector and earth was 2V. Then I tested the amps between the small and large connectors and found no amps. The small spade connector feels a bit loose. I assume that it needs resoldering.

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    Great Pumpkin TR3driver's Avatar
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    Re: Death by Electrocution

    I believe it was riveted originally, you might be able to re-stake the rivet. Could be an open field winding too; that's how my original generator finally died.
    Randall
    56 TR3 TS13571L daily driver
    71 Stag LE1473L waiting engine rebuild
    71 Stag LE2013LBW waiting gearbox rebuild

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    Re: Death by Electrocution

    January 1971. Bought a '60 TR3 a week after I got back from 'Nam. Got married a week later. Tried to start after wedding. Completely dead. In literally 20 minutes with the Practical Hints wiring diagram I traced it to the control box. Removed the box and one of the copper straps had burnt through. Slipped a penny under burnt spot and headed off for honeymoon. Only made it about 50 miles because of massive snowstorm but that is a different story....

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    Re: Death by Electrocution

    Hmm, might be time to change to an alternator. I run an electric fan on my TR4 which the causes the ammeter to move considerably into the negative when idling in heavy traffic.
    I've read and downloaded lots of info on changing to an alternator but have put the upgrade into the too hard basket.

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    Re: Death by Electrocution

    As the new control box is on the way, I am wondering what led to the melting of the A strap on the bottom of the control box. I have read somewhere once that those straps acted as a usable link (not sure they were intended as that) I have a feeling that rather than the ammeter causing the control box melt down on terminal A, it was the control box melt down causing the ammeter to fail. This is because after the melt of Terminal A strap, there was no current supplied by the generator getting to the car and the draw on the battery circuit through the ammeter was too great, and it fried the ammeter. (the ammeter was only rated at 20A I think).
    Rob

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    Re: Death by Electrocution

    If anything fried, it almost always has to be from the battery amperage...as our stock generators don't put out enough to fry anything but themselves in my experience.
    John

    1955 TR2

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    Re: Death by Electrocution

    Quote Originally Posted by jimstr4 View Post
    I've read and downloaded lots of info on changing to an alternator but have put the upgrade into the too hard basket.
    Hardest part IMO is finding a pulley to work with the wide belt. If you've got a buddy with a lathe, it's easy to mod the original generator pulley to suit. Another route is one of the "narrow belt" conversions available from Moss et al.
    Or I believe Moss still sells an alternator conversion kit that includes a wide belt pulley.

    The rest goes pretty easy if you start with a smallish alternator. Here's a few photos of my last conversion, using a Denso alternator from an 89 Suzuki Swift.
    https://imgur.com/a/iiD20
    Randall
    56 TR3 TS13571L daily driver
    71 Stag LE1473L waiting engine rebuild
    71 Stag LE2013LBW waiting gearbox rebuild

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    Jedi Knight
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    Re: Death by Electrocution

    I used this pulley on my alternator. It fits the wide fan belt.

    David

    http://www.ase-supply.com/product_p/ni-p-159.htm

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