How much damage am I likely to have done? (electrical)

[keybaud]

I was removing the ignition only ECU, in preparation to fit the injection one, checking where each connection was and trying to understand which relays it was connected to. Having removed the ECU I turned on the battery isolator, with the ignition off, to confirm which of the red cables to one of the relays were 12V live and which were igntion switched or relay output switched. After a few seconds I noticed a burning smell, so I turned the isolator off, but couldn't find any hot wires or a direct cause of the smell.

 

I double checked all the wiring looking for a short and couldn't find anything. Then I noticed that the alternator was hot and I disconnected the 3 cables I could see to check them. At this point I realised that I may have knocked the 4th earth connection off the alternator earlier, as it wasn't connected, but it may have come off when I removed the other 3....

 

I then realised that I had previously removed the large resistor on the battery isolator that protects the alternator from run on damage should the isolator be turned off with the engine running. I refitted the resistor and turned the isolator back on. I heard the isolator's relay switching as I turned it, so I turned the ignition key part way to see what else still worked:

 

The ignition light was on, but the fuel pump wasn't running. This confused me, as the pump appeared to be driven by the ignition side 12V.

The headlights worked.

I turned the igniton on fully and the starter sounded like it was turning, but it didn't turn the engine. I was now doubly confused.

I then noticed that smoke was starting to come out of the alternator again, so I turned everything off and disconnected the battery and removed the alternator to examine it. There was 0 Ohms between both positive terminals and the earth.

 

I then went inside to bang my head against a wall for breaking a car that had been working fine 24 hours previously.

 

I'm now off to find a wiring loom colour code list, so I can work out what has actually broken. Unfortunately, some of the later work by previous owners hasn't used the correct colour wires, so it may be an awkward job.Lucas Wiring Colours

 

And if anyone knows what the green cable with a single 'PP3' type connector that has been floating around inside my transmission tunnel is for, please let me know.

 

Any pointers/guidance/encouragement/insults gratefuly received.

 

Edited by - keybaud on 12 Aug 2012 20:23:37

[keybaud]

Now I've had a sleepless night thinking over what I could have done wrong, and reading the Build Manual's section on battery master switches at 0230, as I couldn't sleep, I think I've solved some of the problems.

 

I resoldered the wire that had fallen off the isolator resistor and placed it back in the right place, so it should be doing its job properly now. I then had a look at the battery and wanted to slap myself. Whilst testing yesterday, I now think that I accidentally wired the battery the wrong way round when testing the relays! I connected everything back up, with the battery the right way round this time, and the fuel pump kicked into life when I turned the ignition key and the starter motor turned the engine.

 

I'm now off to put the alternator back, so I can see if the engine starts, and then confirm whether the alternator is still charging.

 

Edited by - keybaud on 13 Aug 2012 11:16:44

[Jonathan Kay]

That's a very honest post. Sounds as if things could be worse.

 

I was going to suggest you had the alternator tested off the car, but it sounds as if you've restored normal service to the point where you could safely test it in place.

 

Grandmothers/ eggs etc but I'm sure you have a suitable fire extinguisher in a suitable place...

 

Good luck

 

Jonathan

[keybaud]

Jonathon, thanks for your reply. The good news is that the engine now starts and the alternator is charging. I also now know how to reuse the existing relays for the new ECU, but I'll leave that job until I've had a cup of tea and a chocolate digestive.

[Jonathan Kay]

Like this?

 

Jonathan

[Klunk]

The pp3 clip and green wire fit on you reversing light switch on the gearbox. However, later switches were 2 pin so this may be redundant. If still in use the connector will be live as the switch completes the circuit to gound.

 

Regards,

 

Giles

[Paul Deslandes]

In spite of it apparently all working again you might do well to get the alternator checked by a local specialist. If smoke was coming from the alternator then something was getting very hot and could be a stored up problem for a later and inconvenient date.

[keybaud]

Quoting Klunk: 

The pp3 clip and green wire fit on you reversing light switch on the gearbox. However, later switches were 2 pin so this may be redundant. If still in use the connector will be live as the switch completes the circuit to gound.

 

Regards,

 

Giles

 

Thanks. I don't have a reversing light, which is why this may have never been connected, but I'll try and see where it is meant to go.

[keybaud]

Quoting Paul Deslandes: 

In spite of it apparently all working again you might do well to get the alternator checked by a local specialist. If smoke was coming from the alternator then something was getting very hot and could be a stored up problem for a later and inconvenient date.

 

Paul,

 

Good idea. I'll get it checked out once I've finished the injection conversion.

[Klunk]

The switch is in tailhousing of the gearbox, by the gearlever on the driver's side. Easy to reach from underneath.

 

Regards,

 

Giles