Fail to start disables all electrics

[dmdigital]

Easiest to explain what has now happened twice in the last couple of weeks.

On the Puma, turn the key, starter gives a micro-second burp and then entire electrics on the Puma are dead, nothing, no lights, horn, locks, windows, fans, nothing - it's dead. Disconnect the battery terminals then reconnect and all is OK.

I've put it down to a dead short on the starter and have ordered a replacement.

I've check the earths on chassis and transfer case and everything is nice and clean and tight. None of the leads of the battery are loose, damaged etc.

So I suspect it to be the starter causing the issue, but it seems there must be some other safeguard on the battery circuit that cuts out since everything goes dead when it happens. The fact that de-energising resets something makes me think its either a circuit breaker or a relay in the main circuit but the only two I can think of are the fuseable link on the battery and the starter relay under the driver's seat. But the fuseable link is just that (I believe it is only a heavy duty fuse) and the starter relay I can't see holding everything out.

Any ideas?

[justinc]

hi derek, just had a thought, starter/ ignition switch will cause this too. they aren't renowned for their longevity. haven't you already had one a few years back?
remove the shroud etc and jiggle the switch about while engine is going, see if you can engender the fault?

jc

[dmdigital]

Would that disable power to the entire vehicle though? When that happened before it was the barrel had got stuck but the diagnostic port was still operational as were horn, lights etc.

[Blknight.aus]

check the battery terminals and the other end of the power feeds.

IVe seen corrosion doing a kind of capacitor deal, fine at low amps but tickle the starter solenoid and it blocks off (lets between 3-7V through so you might have led lights still workable if they're not computer controlled) till the load is removed then the voltage comes back up until you go past the amount of current its willing to let flow then it starts again.

Near as i can figure its some freaky thing that terminal protectant causes when it fails between the post and the clamp and begins to oxidise.

[dmdigital]

Already checked and everything is good, clean and no sign of corrosion as far as earths, battery terminals, leads etc are concerned.

[superquag]

Make friends with your local Shaman, Feng Shui Practitioner or Priest...

Exorcism is indicated.

[alien]

check the battery terminals and the other end of the power feeds.

IVe seen corrosion doing a kind of capacitor deal, fine at low amps but tickle the starter solenoid and it blocks off (lets between 3-7V through so you might have led lights still workable if they're not computer controlled) till the load is removed then the voltage comes back up until you go past the amount of current its willing to let flow then it starts again.

Near as i can figure its some freaky thing that terminal protectant causes when it fails between the post and the clamp and begins to oxidise.

X2
As a sugestion it may be in the lead to terminal conection.
It could be hard to find with out a voltmeter when it's playing up

I have had a truck do this to me, it was in the battery isolater.
When running all was good, charging and all lights ect working.
On start up down to 7 volts on the motor side of the isolator.
My above thought is the same thing inside the terminal?

[JDNSW]

I agree, most likely to be a poor earth or battery connection - OK at low currents but voltage drop at high currents is so high that everything thinks there is no voltage at all. Consider - headlights (highest normal load) probably draw of the order of fifteen amps - initial draw of the starter may be 500amps, so 0.02ohms would drop the headlights a barely noticeable 0.3V, but drop 10v with starter current).

John