Electric problem! John C help!!!

On the Spider.

After a winter of refurbishing rear suspension and fitting new front brakes the car is all back together again.
But won't start. Bought a new battery assuming the old one had died over the winter but no different.
Symptoms:
With battery connected in normal way there is exactly the same voltage across the stater motor +ve terminal and the chassis as there is across the battery terminals.
The horn is supposed to work when the ignition is off, but if you try it you can hear the horn make a click and you get disco lights on the dash , the wiper comes on indicators flashing...
If you turn on the ignition a relay clicks continuously in the main relay box and the indicators glow dimly. Various dash disco lights

But, if you connect the battery direct to the rear chassis and the starter motor +ve terminal everything is normal, horn works fine and when you turn the ignition on the fuel pump primes and the engine starts no problem.

To me it sounds like some kind of short circuit/bad earth... But I cannot work it out - driving me mad.

On the Spider.
But, if you connect the battery direct to the rear chassis and the starter motor +ve terminal everything is normal, horn works fine and when you turn the ignition on the fuel pump primes and the engine starts no problem.

Hi Rupert,

I don't know much about Spiders, but you clearly have some form of bad connection somewhere.
Am I right in thinking the battery is in the front of the Spider ???
If so .... with the battery in its correct place, you need to do some meter checks.
As you say, you have the same voltage at the starter solenoid and chassis as you do at the battery.
Leave your meter connected to the starter and chassis, and try the starter ... or horn................ I suspect the voltage reading on your meter will die, or at least drop considerably.
If this is the case, I suspect you have lost an earth strap from the chassis to the engine or where the earth lead from the battery connects to the chassis ...... or a bad connection either on the 12v battery terminal, or the starter........ or as the GTA a connection box possibly on the bulkhead.
BTW ..... is there a battery cut off switch on the Spider ??? ....... if so you could try putting the two heavy wires together on one bolt ..... it could be the switch had gone high resistance ..... this is quite a common problem on these switches.
There are a few things for you to try, but basically although you have a voltage from the battery to the starter .... it cannot take any form of current due to a high resistance connection.
I hope this is of help to you ....... let us know how you get on.
John

Well thanks John,
I tried bypassing the on off switch just in case, but in fact it was the earth strap from the battery to the chassis.... One I had already undone and reconnected!
Filed down the faces and covered it in Vaseline.
Everything back to normal now so thank you for your help & logic

As Simon always says CHECK YOUR EARTHS !!!

Well done Rupert ...... glad you got it going.

Although most members emphasis checking Earths, it should also be remembered that the live !2 volts path to all parts of the electrical system is just as important as the Earth return.
Any high resistance in the 12v supply to the Starter or Alternator, will give exactly the same fault as a high resistant Earth connection.

[Alpineandy]

Any high resistance in the 12v supply to the Starter or Alternator, will give exactly the same fault as a high resistant Earth connection.

You are of course completely correct but spending hours faffing around only to find it was an iffy earth is far more annoying than finding another fault. So although it's not always the problem, it's safest that it's the 1st thing to check