TVR Vixen - Electrical System
During the first couple of months of owning this car I was plagued by minor electrical faults - mostly due to loose connections behind the dash. The trouble was that each time you fixed one you disturbed another and it took a couple of months to remake all the poor connections. The worst time was when my wife returned with the car on a transporter having called out the recovery service twice - the first time they claimed it was fixed. This involved a very embarrassing experience as she stopped in someone's driveway rather than block the road while she went to telephone. The house's owner returned in the meantime and thought that her husband had bought her a present as she had always wanted an old TVR.
Engine Bay Wiring
The most comprehensive work I have done to the wiring was when I took the body off. One of the miscellaneous minor connections between body and chassis is the electrical connections in the engine bay. I labelled some of these but as some wires weren't connected to anything it wasn't obvious where they should go. One in particular went nowhere - I couldn't find another white and blue wire anywhere. I decided that I would unwrap the wiring loom in the engine bay to sort it out as that would give me a chance to include all the extra bits like wiring for the electric fan and electronic ignition. I started by unwrapping the branch to the solenoid and discovered that the whole arm of the wiring loom had been extended. The ring terminals were still inside the loom and the mystery wire was connected to another of a different colour. I haven't worked out why the loom has been extended as there are no signs of the solenoid having been moved. Perhaps it was made for an S2 which has the starter on the other side? In the end I replaced most of the terminals in the engine bay with new ones soldered on and replaced and repaired a number of wires.
Wiring Diagram
I also found during this procedure that the wiring diagram that I had wasn't accurate and I ended up drawing a new one. I also have a version that I think is how mine left the factory - but from my experience it may not be the same as any other car. If in spite of that you'd like to see it, click here.
While doing this I had a number of discussions with other members of the TVR Car Club about the wiring and the consensus was that there is a serious shortage of fuses with a lot of wiring under the dash permanently live and unfused. I have added a couple of in line fuses where the main supplies from the voltage regulator enter the car.
The wiring on the car had been professionally altered to use an alternator when I bought it and while working on the engine bay I had a good look at how this had been done. In essence the charging circuit on both an alternator and a dynamo is a ring with the regulator and battery in it. With an alternator the regulator is in the back of the alternator and with a dynamo it's in a box halfway around the circuit. The regulator in a dynamo circuit is also a junction box and this is where the main power supplies to the car are connected. With an alternator circuit they are normally connected near to the battery. Both the dynamo and alternator are partly operated by the field current and on an alternator this flows through the ignition warning lamp.
Conversion from dynamo to alternator therefore involves connecting all the thick wires at the regulator together and connecting the two thin wires together (ignoring the earth). The thick wire connection completes the alternator charging circuit and connects it to the vehicle wiring. The thin wire connection connects the alternator field connection to the ignition warning lamp. At the dynamo end the thick wire is connected to the large terminal on the alternator and the thin wire is connected to the small terminal on the alternator.
The alternator circuit requires some current through the warning lamp bulb to operate (even though this is not enough to light the lamp) if the bulb is loose or blown the battery will not charge. I believe cars fitted with an alternator from new have a resistor across the warning lamp to avoid this difficulty. A loose bulb was the cause of my wife's return with the car on a breakdown trailer.
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Having sorted all this out and added extra fuses I decided that if I were doing this conversion there is a more elegant solution. If you take an old voltage regulator and remove the works the main connections can be made inside it. Fuses for the main power supplies could also be put inside it. This would retain the original appearance and there would be no need for modification of the wiring loom at all.
There is one other question about alternator conversions which worried me slightly and that is that an alternator is capable of exceeding the maximum current capacity of the charging circuit (about 25 amps). The Lucas LRA101 alternator (a rebuilt 17ACR) fitted to my car has a maximum output of 34 amps. Information I found on the web however suggests that in practice this isn't a problem because the alternator is fitted for the better output at low revs rather than the higher maximum output. There still might be problems if you were to get a jump start for a completely flat battery - in which case you turn all loads off (as these increase current in part of the circuit without it showing on the ammeter) and watch the ammeter carefully.
Additional loads
The alternator conversion raises the question of where you should connect additional loads. If you connect them at the voltage regulator junction they will still register on the ammeter but they may help to overload the charging circuit without you knowing. As the ammeter only measures current to the battery the part of the charging circuit the other side of the regulator junction will carry the current to the battery as well as the current being used by the car. I decided to connect the extra supplies (fan and radio) at the solenoid.
Maybe it would be simpler to stick with a dynamo.
When I bought the car the Brake Fail Warning Light stayed off - as it should - but I noticed there was no connection to the PDWA. When I made the connection the light still didn't come on as the bulb had been removed. When it was replaced the warning light worked again but there should have been a hand brake warning light which in practice tests the circuit every time you use the car. Mine was missing but another owner told me that it was a motorcycle brake lamp switch. Easy access for fitting the switch was gained by removing the body. The switch is fitted to a diagonal chassis tube in front of the hand brake and connected by a long pull wire to a hole low down on the hand brake lever.
The only thing to have gone wrong since I reassembled the car is the starter solenoid. It didn't quite let me down Repeated flicking of the ignition switch seemed eventually to bounce the contacts properly together. I fitted a new one - but I took the old one to pieces. I drilled out the rivet ends and unsoldered a couple of wires - cleaned the contacts and reassembled with small bolts. Now I have a spare.