+2 Spyder: Positive Earth?

[Bahtatboy]

You have me on your Shrodinger volt thing! Not sure what it is. But no matter. what you are generally saying, I think, is that no matter what you do or where you make a connection, the voltage drops to 6V.

IF this is the case, then you have possible serious problems with the car as it indicates that anything on the car will drop to 6V. Does the car start? Do you have headlights etc? On what you say, it is doubtful - iF that is, the drop applies to the whole car. It maybe that there is a drop just on the couple of circuits you are using.

Voltage drop is complex and requires testing a circuit at various points, it also requires that everything is resistance tested. Two contributing factors to voltage drop: Earthing and Corrosion with Earthing head up the list. Start at the battery earth and clean the metal down to bright steel. Do the same wherever the earths are for the crl circuit

Disregard the Shrodinger volt reference. Yes, whenever a connection is made, the voltage drops to 6V. The car runs fine, and all the important things work -- so the drop seems to occur on the fuse box and on the heavy cable on the relay in the footwell ... so I too am now suspecting the earth. Also, of the 8 fuses in the fusebox in the glove box, only two are live (at least with the ignition on -- haven't checked yet with the engine actually running) -- all have cables running to them which presumably are meant to do something; the only things which obviously don't work at present are the interior lights and the heater fan -- just before I bought the car the dealer tried to get the heater to work, which involved having a re-cored matrix fitted (which, I believe, required having the dash off), so I suspect that during that work some electrics behind the dash were disturbed. I don't want to take the dash off at this point (that'll be a winter job), but if I can get to the headlight switch and take a power feed from there, and put an in-line fuse to the HUD, then surely (surely?!) that should work. I'll clean as many earth points as I can, including the main one in the boot adjacent to the battery.

[HCA]

Yes, I imagine you have quite a few issues to sort. Britain back in the day could not wire a car to save their lives. the industry was so caught up in saving a yard of wire here and there that resulted in the absolute minimum of fuses and doubling up of devices. Something that lingers on today with UK house wiring that still lags behind most the RoW.

If you plan on a rewire in the future, then I suggest you run two 3mm thinwall cables - a black and red directly from the battery into the cabin, terminate the black on a simple 6mm nut and bolt, and the red onto a small modern fuse block and each time you need a connection take it off a new fuse and return it to the nut and bolt with a ring connection, wrap it up well behind a carpet. This will minimise the nonsense you are having.

For the future, especially if you have a friend who is good with electrics, consider making up a new proper wiring loom of thinwall cable, a fifteen way fuse box, a single earth point for everything and if you do use the chassis as an earth conduit - tin the places where you connect. No need to follow the useless wiring diagram and the nonsense of piggybacking devices: just take a two wire circuit to each device and still your loom will be half the size of the original...

[Bahtatboy]

Yes, I imagine you have quite a few issues to sort. Britain back in the day could not wire a car to save their lives. the industry was so caught up in saving a yard of wire here and there that resulted in the absolute minimum of fuses and doubling up of devices. Something that lingers on today with UK house wiring that still lags behind most the RoW.

If you plan on a rewire in the future, then I suggest you run two 3mm thinwall cables - a black and red directly from the battery into the cabin, terminate the black on a simple 6mm nut and bolt, and the red onto a small modern fuse block and each time you need a connection take it off a new fuse and return it to the nut and bolt with a ring connection, wrap it up well behind a carpet. This will minimise the nonsense you are having.

For the future, especially if you have a friend who is good with electrics, consider making up a new proper wiring loom of thinwall cable, a fifteen way fuse box, a single earth point for everything and if you do use the chassis as an earth conduit - tin the places where you connect. No need to follow the useless wiring diagram and the nonsense of piggybacking devices: just take a two wire circuit to each device and still your loom will be half the size of the original...

Merci beaucoup, Hal. It was rewired with a new loom 10 years ago, but I don't how well (I've only just bought it) -- I'll assess if fully when the nights draw in.

[Bigbaldybloke]

Note that a USB socket should put out 5 volts at 1 or sometimes 2 amps so 6v out of the socket with no load sounds about right.

[Craven]

Yes, I imagine you have quite a few issues to sort. Britain back in the day could not wire a car to save their lives. the industry was so caught up in saving a yard of wire here and there that resulted in the absolute minimum of fuses and doubling up of devices. Something that lingers on today with UK house wiring that still lags behind most the RoW.

If you plan on a rewire in the future, then I suggest you run two 3mm thinwall cables - a black and red directly from the battery into the cabin, terminate the black on a simple 6mm nut and bolt, and the red onto a small modern fuse block and each time you need a connection take it off a new fuse and return it to the nut and bolt with a ring connection, wrap it up well behind a carpet. This will minimise the nonsense you are having.

For the future, especially if you have a friend who is good with electrics, consider making up a new proper wiring loom of thinwall cable, a fifteen way fuse box, a single earth point for everything and if you do use the chassis as an earth conduit - tin the places where you connect. No need to follow the useless wiring diagram and the nonsense of piggybacking devices: just take a two wire circuit to each device and still your loom will be half the size of the original...

Merci beaucoup, Hal. It was rewired with a new loom 10 years ago, but I don't how well (I've only just bought it) -- I'll assess if fully when the nights draw in.

Not a good idea at all. If the starter main earth is lost, poor connection, it will pull its very high current through any available path. Your black 3mm cable will go up in smoke.

[RichardS]

Yes, I imagine you have quite a few issues to sort. Britain back in the day could not wire a car to save their lives. the industry was so caught up in saving a yard of wire here and there that resulted in the absolute minimum of fuses and doubling up of devices. Something that lingers on today with UK house wiring that still lags behind most the RoW.

If you plan on a rewire in the future, then I suggest you run two 3mm thinwall cables - a black and red directly from the battery into the cabin, terminate the black on a simple 6mm nut and bolt, and the red onto a small modern fuse block and each time you need a connection take it off a new fuse and return it to the nut and bolt with a ring connection, wrap it up well behind a carpet. This will minimise the nonsense you are having.

For the future, especially if you have a friend who is good with electrics, consider making up a new proper wiring loom of thinwall cable, a fifteen way fuse box, a single earth point for everything and if you do use the chassis as an earth conduit - tin the places where you connect. No need to follow the useless wiring diagram and the nonsense of piggybacking devices: just take a two wire circuit to each device and still your loom will be half the size of the original...

Merci beaucoup, Hal. It was rewired with a new loom 10 years ago, but I don't how well (I've only just bought it) -- I'll assess if fully when the nights draw in.

Not a good idea at all. If the starter main earth is lost, poor connection, it will pull its very high current through any available path. Your black 3mm cable will go up in smoke.

I agree with Craven, much better to have multiple earthing points rather than relying on one. My old post about earthing is still pertinent and electrics have been trouble free since. The only update is that I now activate the starter solenoid through the redundant bulkhead solenoid, to reduce the load on the ignition switch.
Link to old post http://www.lotuselan.net/forums/posting ... 19&p=92600
Good luck!
Richard

[HCA]

Not a good idea at all. If the starter main earth is lost, poor connection, it will pull its very high current through any available path. Your black 3mm cable will go up in smoke.

Now you are being an alarmist for the sake of it.

Pray explain how a starter motor, having lost its earth return, is going to find an independent wire sitting in the cabin from the battery supporting a USB, radio and a few other ancillaries..?

Exactly, it cannot.

The OP here is nervous anyway with his situation, we should not be making it worse by talking about starters losing their earths. Besides, IF such a thing were to happen, there would be many other problems, but the independently wired USB and radio would not be one of them!

As to the next doom and gloom post, in effect the Elans as they are in standard electrical trim, have a single point of contact for the earth - it is where the negative cable from the battery joins the chassis. What happens [yes in the most highly unlikely event] that this gets damaged or corroded?

I repeat that one single and tinned point of connection to the battery negative is as good as it gets.

[Craven]

Not a good idea at all. If the starter main earth is lost, poor connection, it will pull its very high current through any available path. Your black 3mm cable will go up in smoke.

Now you are being an alarmist for the sake of it.

Pray explain how a starter motor, having lost its earth return, is going to find an independent wire sitting in the cabin from the battery supporting a USB, radio and a few other ancillaries..?

Exactly, it cannot.

The OP here is nervous anyway with his situation, we should not be making it worse by talking about starters losing their earths. Besides, IF such a thing were to happen, there would be many other problems, but the independently wired USB and radio would not be one of them!

As to the next doom and gloom post, in effect the Elans as they are in standard electrical trim, have a single point of contact for the earth - it is where the negative cable from the battery joins the chassis. What happens [yes in the most highly unlikely event] that this gets damaged or corroded?

I repeat that one single and tinned point of connection to the battery negative is as good as it gets.

I feel any recommendation on this forum than can possibly decrease the safety of these fibre glass body cars should be challenged.
Just one of many examples of an unobvious negative chassis connection is the Radio chassis, the caveat that all auxiliary equipment always be isolated from the metal chassis should have been made clear.
Battery return via the chassis connection in the boot becoming open circuit or very high resistance is common fault on these old cars. Bypassing this connection is not a good idea unless made with a suitably rated cable that will support full starter current.

[HCA]

Now you are talking funny, to be polite!

What is unsafe about a GRP body? All cars, composite or steel, use the chassis as an earth conduit around the car. What is this nonsense that a radio must be isolated from the chassis? And as for the battery negative going open circuit in older cars being a common fault is fantasy, again being polite. How it would go open circuit beats me, but I guess you know something I do not. If the battery goes open circuit, the starter motor - or any other motor - will not work.

I do concede that battery cells can die, making the battery open circuit, but it is not common.

Now high resistance might be another matter and nothing to do with a car design and is purely down to maintenance. It is for this reason that I always advocate tinning the joint on the chassis/body.

I suggest that you pick up any car wiring diagram - try one for an Elan - and you will see the battery neg go to a point marked 'earth' and various other devices will show the same, even the radio! There is no separate earth cable except where aftermarket devices might have been added, and even then not always.

[Slowtus]

Apprentice, Electrician, Electronics Tech in the RAF, Computer Tech thereafter etc...residential, commercial and auto electrics, HNC and C&G, even designed and built the "box" allowing astronomers from all around the world to hook up their imaging devices to various infrared telescopes, including the CFHT (Canada France Hawaii Telescope)

The list is long because I started as a sparky in 1963. Along the way I gained some knowledge but have never (and will never) claim to be an expert and do learn something new every day in these areas.

That said, some of the above will have me communing with Herr Ohm, Kirchoff and their friends for a short while

HCA , the reference to isolating the radio probably goes back to the days when you bought a brand new (3 watt ) radio which was negative earth and were installing it in positive earth car.

Or not...

[Craven]

HCA.
You wrote:
If you plan on a rewire in the future, then I suggest you run two 3mm thinwall cables - a black and red directly from the battery into the cabin,
I wrote:
Not a good idea at all. If the starter main earth is lost, poor connection, it will pull its very high current through any available path. Your black 3mm cable will go up in smoke.

You wrote:
Pray explain how a starter motor, having lost its earth return, is going to find an independent wire sitting in the cabin from the battery supporting a USB, radio and a few other ancillaries..?
I wrote: Just one of many examples of an unobvious negative chassis connection is the Radio chassis

You wrote:
‘ What is unsafe about a GRP body? ’
Ans: in the context of this post overloaded wiring can cause a fire, GRP is highly flammable.

You wrote:
‘ And as for the battery negative going open circuit in older cars being a common fault is fantasy,’
I actually wrote : Battery return via the chassis connection in the boot becoming open circuit or very high resistance is common fault on these old cars.

You wrote:
What is this nonsense that a radio must be isolated from the chassis?
I actually wrote : Just one of many examples of an unobvious negative chassis connection is the Radio chassis

You wrote:
As to the next doom and gloom post, in effect the Elans as they are in standard electrical trim, have a single point of contact for the earth - it is where the negative cable from the battery joins the chassis. What happens [yes in the most highly unlikely event] that this gets damaged or corroded?
I wrote:
Battery return via the chassis connection in the boot becoming open circuit or very high resistance is common fault on these old cars.

Extra 3mm black cable will become a low resistance battery return path if the connection in the boot to the chassis is lost. If the radio is powered from this new supply, the 3mm black cable will make a direct connection to the car chassis via the radio chassis.

[Craven]

Slowtus.
Your CV is impressive, I have been in the game somewhat longer. My last post/position involved improving the sensitivity and resolution of Mass spectrometers and Gas chromatographs. Chasing currents in the femto amp, 10 to the minus 15 amp range is most enlightening, now where have those electrons gone.

[Slowtus]

Slowtus.
Your CV is impressive, I have been in the game somewhat longer. My last post/position involved improving the sensitivity and resolution of Mass spectrometers and Gas chromatographs. Chasing currents in the femto amp, 10 to the minus 15 amp range is most enlightening, now where have those electrons gone.

All good British training...