S130 mystery warning light fault

[checkrail]

I have finally run out of patience with this, I will pull the bulb and hope that it doesn't upset anything else

Thanks for all your suggestions John

[billwill]

It could be of course that it was designed to behave that way, to prove to you that the bulb is working, so you can place greater reliability on its brake-warning capability.

[Spyder fan]

It could be of course that it was designed to behave that way, to prove to you that the bulb is working, so you can place greater reliability on its brake-warning capability.

Bill,
I always thought highly of your auto electrical acumen

Feeling let down at this point

Checkrail the OP, has a battery isolator fitted. So when it’s armed to allow current to pass from the battery there should be no action unless the ignition switch is in the on position or perhaps the accessory position.

What happens at the moment is that when the isolator is switched on for some reason the brake warning light illuminates, this shouldn’t happen.

The Sovy low fluid has been deleted but the wiring is still there, the dashboard light should not come on, but it does. It’s a mystery as to why it illuminates. Your failsafe theory would be sound on a much later vehicle, never on an Elan of this vintage….. but keep thinking and trying to solve, it’s intriguing me and no doubt others including the OP who is no doubt very frustrated at this point ……

PS, how’s the ULEZ? Have you taken out a contract on the mayor yet?

[checkrail]

One other variation today, tested the warning light terminals again with the meter --- no current showing. They had 12v yesterday.

John

[mbell]

Does the clock keep time with battery disconnected?

If the battery switch is off everything should be off. The only standard thing I can think you might want to stay live is the clock so it keeps time. If it keeps time, then there might be a small bypass circuit running the clock. Which might be finding a way into the rest of the system when off. Trigger the strange behavior.

[billwill]

Since the original car does not have a battery isolator, the actual circuitry is a complete mystery. Especially if it is so rigged that turning the ignition on closes the isolator relay. Without having a long think, which I'm not going to do, I can't even see how that could be rigged. In fact I wouldn't call that an isolator at all, since it must be not isolating power to some contact on the ignition switch. i.e there is still power behind the dashboard..

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Re ULEZ, I am already inside the ULEZ zone by about 200 yards, adding outer London will make no difference to my problems about it. I can't get my exempt Lotus out of the garage without moving the nonconforming Diesel 7-seater onto the road, where there is a chance that it might be seen by the cameras, So basically I can't get either car out for free.

[h20hamelan]

Bill, here in the wilds of fire revenged BC. We are allowed to move anything within 200ft of our property on the public road. Wonder how long this will last for you?
ULEZ

[ericbushby]

Hi All,
Sometimes when there is a battery isolator, yet you want to keep the clock and alarm systems running a small fuse, say 2 Amp, is fitted bypassing the isolator. This is unlikely to cause a fire in the case of an electrical fault but the starter motor, lights etc. will not work. Just a thought. Good luck,
Eric in Burnley
1967 S3SE DHC

[checkrail]

The clock runs all the time bypassing the isolator and has its own fuse, the PO has done several electrical improvements including window relays.

[Spyder fan]

I think it would be useful to forget the battery isolator for a moment and assume that the car is standard.

What’s happening is that the brake warning light illuminates when the ignition is off. When the ignition is switched on the light goes out. Somehow the lamp is getting voltage that disappears when the ignition is switched on.

Auto electrics can be a dark art

[checkrail]

I started the engine and ran it up to temperature and now that light was on the whole time.
Everything else worked as it should, that light still works even without the fuse in place