410 Wiring

[Roger Morrall]

Brian

That could well be the case. Especially if all else and the ammeter works as it should. I had a number of wiring diagrams, one of which I think purported to be for the 409, all of which are now with PEU186Fs new owner but I’ve never ever spotted one that included any details of the push button gear change mechanism. I wasn’t even aware that the early 410s retained it but one lives and learns. It also wouldn’t have been beyond Bristols to use a left over 409 wiring harness in a 410.

While you’re thinking about all this spare a passing thought for your ignition switch and the load it’s handling and marvel that it’s lasted as long as it has.

[DODD]

Roger,

I don’t think any of the 410’s retained the push button gear change and I also have no doubt that Bristol would have used all of the wire harnesses from previous models which they had in stock and quite rightly, as very little changed between earlier models.

Looking at the loadings going through the ignition switch gives me some concern. It is my intention when adding the isolation switch to the fuel pump, I will also be installing a relay and fuse to the circuit, this will be in addition to a few extra fuses as required.

Brian

[Sam410]

Originally Posted by DODD

Looking at the loadings going through the ignition switch gives me some concern.

To possibly fuel your concern, I have got through two ignition switches in the near 90,000 miles I have had my 410. The original (or at least the one fitted when I bought the car) expired around 12 years ago, its NOS replacement lasted about 8 years and I fitted a new replacement then. The modern one has one less terminal posts than the older design, so there was a degree of head scratching involved to work out which wires could be combined.

When they start to burn out there is an unmistakable fishy smell as the plastic of the switch overheats. The first one finally failed in France and I spent the next 1000 miles having to hotwire the car at every stop!

[Roger Morrall]

The load on the ignition switch is bad enough, consider also the back emf that is generated when a dc motor is switched off.

Having experienced an ignition switch failure I arranged for the switch to operate a very heavy duty relay which in turn fed the fuse that "protects" the green switched circuits directly from the brown battery circuits.

I also comprehensively increased the number of fuses so that each circuit was appropriately fused - which turned out to be the devil of a job, one that would have been very much easier if I could have had the car on a lift, but that’s another story.

My failed switch was I believe an original fitment and probably of much better quality than anything you’d find today. It’s failure pattern showed up through a very intermittent apparent misfire, initially so short that one hardly noticed, but the length of the misfire extended gradually over a period of several years until finally the car would come to a stop yet mysteriously would restart after a few seconds after the switch had cooled down.