Blown ammeter shunt - now won't start. And must-read safety tip on brakes!!!!
I had a (near) total electrical failure in my '76 Corniche the other day: the engine, lights and steering died on me whilst driving - this was quite scary. Fortunately, I was just slowing down on approach to a lighted village and there was a wide low pavement for me to pull safely onto. The RAC mechanic diagnosed a blown ammeter shunt and, unable to fix it, trailered me home (see VERY IMPORTANT note at bottom!!!!).
The salesman at Flying Spares said that ammeter shunts get frazzled when owners jump start their car or attach booster packs. (He suggested always turning the headlamps on when jumping RRs.)
Now, for all the years I've owned this car, the headlamps have always had a slight flicker and the ammeter has always had a small but noticeable waver. It would appear that the connector between the heavy-duty brown and white wire and the ammeter shunt inside the car got frazzled at some point and has been arcing ever since - finally blowing on me the other day. That is my reading of the situation.
Anyway, I have replaced the ammeter shunt but now nothing happens when I turn on the ignition switch! The battery is charged, the interior and exterior lights work, the battery isolator is switched on, and I can hear the fuel pump working. I have checked all the fuses in the cabin but can find nothing amiss. i have searched this forum, but can't identify anything specific to this. I'm just wondering if there's some other 'blowable' component that needs to be checked?
Any thoughts will be most welcome.
IMPORTANT SAFETY TIP
When I pulled the car up, the brakes were working fine. I left the car pointing slightly downhill so that i could roll onto a trailer. When the RAC guy turned up he told me to cover the foot brake when I took off the handbrake. I did, but it made no difference. The car had no brakes at all and despite standing on the footbrake so hard I gave myself cramp, the car continued rolling!!!
I thought that the residual pressure in the accumulators would be more than enough to stop me, but there was nothing. fortunately, I just drove up the slope of the trailer and stopped, but I was shocked at how quickly this could have got out of control. Please be aware of brake failure when you have an engine problem and be ready with the handbrake and, in extreme situations, taking the car out of neutral and selecting 'park'!
1976 Bentley 1A Corniche (Rolls Royce conversion)