J R Martin Posted April 30, 2020 Report Share Posted April 30, 2020 TR4 Electrical Problems, Good afternoon all, I am currently having electrical problems with my late 1964 TR4 (CT 32458O). I am going through each unit connected to the main 35A fuse and think the voltage stabilizer may be at fault as the small instruments, the indicators and the wipers all stopped working. I realize the wiper motor is fed direct from the same feed as stabilizer. The car remains + earth and the main fuse blows instantly the ignition is switched on. I have owned the vehicle for about 45 years and so I am fairly confident the loom is original and have no recollection of ever replacing the stabilizer previously. My problem is that the Auto – Wire wiring diagram shows wires going to and from the stabilizer as green, green/ black and black whereas mine are yellow,, yellow / purple, yellow / green and purple. The stabilizer has 4 male Lucar terminals and has “Made in England”, 6 RA 33213D (or 0), 12V 10 62 stamped on the side. Can anyone help me or make any constructive suggestions please? Meanwhile, keep a low profile and stay well John Quote Link to post Share on other sites
RobH Posted April 30, 2020 Report Share Posted April 30, 2020 (edited) Those colours and the numbers suggest you are looking at the overdrive relay rather than the voltage stabiliser John, though the colours are not quite as per the drawing. As for your fault I suggest you start by finding the voltage stabiliser itself in the other footwell and remove all three green wires. Find which of the green wires is the supply ( use a small bulb for that ) and then check the remaining two green wires for a short to earth. If they both seem OK then suspect the stabiliser. Edited April 30, 2020 by RobH Quote Link to post Share on other sites
tthomson Posted April 30, 2020 Report Share Posted April 30, 2020 (edited) Hi John, The fuse that is blowing! Does that connect light green and mid green wires? (or is it the ones connecting Mainly red wires? - i.e side light circuit). If the fuse relates to green wires then the range of devices that could be faulty (assuming no major wiring changes have been made) are as follows: Voltage stabiliser, Turn flasher, Wiper motor, The loom. (The other devices on this 'Green' circuit all have switches in the supply) The stabiliser is typically a little flat metal can, with two connection points, labelled B (battery) and I (instruments), and is earthed via the can screw fixing, and is normally found behind the dash on the RHS near the bulkhead. (A torch makes it easier to see and identify) To test this, pull the Green/Black wire from the 'I' connector, pull out the turn flasher unit, AND disconnect the green wire to the wiper motor. Check the ignition. If the fuse blows, then the problem is with the stabiliser. If the fuse does not blow, the fault lies with one of the other devices. Reconnect the Green/Black wire to 'I' on the stabiliser, and check again. If the fuse blows it is a problem with either the fuel gauge or the temperature gauge circuits If the fuse is OK, reconnect the flasher unit to test the turn circuit, or reconnect the wiper motor to test the wiper motor system. Good luck with it, and let us know where the problem was found. TT Edited April 30, 2020 by tthomson Quote Link to post Share on other sites
J R Martin Posted May 3, 2020 Author Report Share Posted May 3, 2020 Hello Tony, Many thanks for your extremely useful and prompt resonse. I would like to update you and seek more of your expert advice, please:- The fuse that is blowing is connected to the green wires and is rated at 35A I have pulled the green/black wire from the stabilizer (why is it in such a difficult location?), removed the flasher unit and isolated the wiper motor as you suggest and the fuse does not blow. However after a time a small amount of smoke emanates from the fuse box ( repro unit just fitted as I thought the original one was somehow leaking to earth). I have traced the wiring near the flasher unit after it leaves the main loom and I think it may be suspect with the insulation, I would describe as hard and brittle. Looking at the wiring diagram, if this wire is suspect before it reaches the flasher unit and is somehow earthing that would give rise to the problem I have just described? What do you think could be the problem and how could it best be solved? I guess a totally new loom would be the ultimate solution but that seems an overkill solution. Replacing the green wire from the stabilzer unit to the flasher is something I think I could do quite easily but the wiring diagram shows a small "box" in the line just before the flasher and another just before the wiper motor, Are these "boxes" by chance bullet connectors? The wiper motor circuit does not have its own fuse which surprises me, would not an inline fuse not be sensible and if so what should be the size of fuse? I look forward to your reply. Thanks and regards John. PS, I have purchased new stabilizer and flasher units, just in case and will get the wiper motor refurbed, bearing in mind these are all more than 50 years old, but what is your opinion, re-use the original units or fit the repro ones? Quote Link to post Share on other sites
tthomson Posted May 3, 2020 Report Share Posted May 3, 2020 (edited) Hi John, The small boxes shown on the wiring diagram are indeed bullet connectors. Replacing the loom is a seriously difficult job. Replacing a wire is not too difficult. You say the Green wiring is experiencing the problem, so this is how I see it. When you say that smoke emanates from the fuse box, is this when the various items mentioned are disconnected? If so the voltage stabiliser is very suspect To find the problem: Start with ignition off. Disconnect the two green wires from the fuse so that it is not supplying any of these circuits. Then with igintion on, touch one green wire at a time back onto the fuse box to see if sparking occurs. (It should not!). Any sparking would indicate a fault in that circuit. Remove this wire and test the other green wire to ensure that it does not also cause a problem. If ok, reconnect this 'no problem' wire, and replace any blown fuse. You are now in a position to find the culprit circuit. Check the brake lights work. If so the other green wire (the disconnected one) is connected to the voltage stabiliser which is the key suspect. If the brake lights do not work, then the problem is to do with the brake light circuit. If Brake lights work, disconnect the wires from the B connection on the voltage regulator, and connect these wires together. (Use a piece of wire to effect a temporary connection) reconnect the other green wire to the fuse. With ignition on, reconnect the wiper motor. The fuse should not blow, run the wiper motor to test the circuit is OK when operating. Any problem then this is the faulty circuit Now connect the flasher unit. The fuse should not blow, use the indicators to ensure these are working ok. Any problem then this is the faulty circuit. If these prove to be OK, all that is left is the Voltage stabiliser, and therefore the fault could be either the voltage stabiliser or the wire to it (including damaged or loose connectors inappropriately touching something else). I hope that helps. Kind regards Tony Edited May 3, 2020 by tthomson Quote Link to post Share on other sites
tthomson Posted May 3, 2020 Report Share Posted May 3, 2020 Hi John, The question you raise about fuses, is one that regularly occurs, and the simple answer is that fuses over time may blow from cyclic thermal stress, so they are not ideal in critical circuits. Triumph (along with most manufacturers at the time) put used two fuses, one for the side lighting circuits and one for auxuliary circuits. Lighting and ignition were not fused so that a car would not suddenly stop or lose headlights while travelling at speed. Modern vehicles have a lot more electrical systems and the use of fuses has become far more common. I have about 20 fuses on my TR4A. These are for things I have added and to isolate any failed device so that it cannot start a fire. Most of the original devices on our TRs will blow one of the to fuses if they fail, and that is enough to warn you that there is a problem needing urgent attention, but this does not pinpoint the problem (as you have discovered). When I rebuilt my 4A, I increased the number of fuses to accommodate the additional functionality, but have not made significant changes to the ignition or lighting systems other than using relays to reduce the current through switches. Kind regards Tony Quote Link to post Share on other sites
J R Martin Posted May 3, 2020 Author Report Share Posted May 3, 2020 Hello again Tony, Many thanks once again for your prompt detailed useful comments. You ask if the smoke from the fuse box occurs when all the various items are disconnected, well the answer is "yes" but the fuse didn't blow. If this indicates the voltage stabilizer is suspect as you suggest then my simple mind would say why not change it for a new unit that I have already just purchased? I know this may not solve the problem yet, this is the approach used on modern cars, would not be too difficult to do and would hopefully eliminate one suspect? Thanks again , John Quote Link to post Share on other sites
RobH Posted May 3, 2020 Report Share Posted May 3, 2020 More to the point John - you have to ask why did you get smoke from the fuse box and what damage is that likely to have caused. Obviously the smoke indicates that some plastic component was getting very hot. Either it was a wire in which case the insulation on that must now be questionable or it was one of the clips which hold the fuse, in which case the plastic housing round it must now be somewhat melted. Do not ignore it as you may now have a situation where a fire could occur at some later date if the insulation fails completely, even after you cure the fuse-blowing fault. Inspect everything and replace any part that looks charred, melted or otherwise damaged. You should be made aware that there are differences in fuses. The automotive glass fuses to be used in our cars are specially designed to blow at the rated current. Normal glass fuses with the same current rating are designed to carry that current indefinitely without blowing so a fuse marked 35A may last several seconds with as much as 100A flowing. The two can look very similar but you must use the right ones to protect the wiring. Quote Link to post Share on other sites
John Morrison Posted May 3, 2020 Report Share Posted May 3, 2020 ""However after a time a small amount of smoke emanates from the fuse box ( repro unit just fitted as I thought the original one was somehow leaking to earth)."" is there a clue here? John. Quote Link to post Share on other sites
trchris Posted May 3, 2020 Report Share Posted May 3, 2020 Hi John The way to find a fault in the circuit you suspect is shorting to earth is by removing the fuse which feeds and replacing with a bulb the bulb will glow if a short is present allowing you to disconnect each wire in turn until the bulb goes out then you know where the fault lies Chris Quote Link to post Share on other sites
tthomson Posted May 4, 2020 Report Share Posted May 4, 2020 +1 for trchris's suggestion Quote Link to post Share on other sites
J R Martin Posted May 5, 2020 Author Report Share Posted May 5, 2020 Many thanks Tony and trchris, I will follow your suggestions and report back in due course Cheers John Quote Link to post Share on other sites
Phil Pope Posted June 12, 2020 Report Share Posted June 12, 2020 John is having some tech gremlins to stay so I am passing on his reply below: Hello Tony, Many thanks for your detailed and prompt responses, they were very much appreciated. Following your instructions I was able to trace the fault down to a breakdown in the insulation in the feed to the wiper motor. This has now been rectified and the whole system works as it should. Thanks again, stay safe and keep virus free, Cheers John Quote Link to post Share on other sites
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