Testing brake failure light

Technical discussion on converting internal combustion to electric
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evric
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Testing brake failure light

Post by evric » Mon, 20 Oct 2008, 06:23

Basically, what they are looking for is that the brake light functions the same as it did before the vehicle was modified. This should be easy enough to organise a relay system to allow the lamp to light when the ignition switch is in the ON position and then off as you turn the key to START, then remain of when returning to ON. The light must still, of course, function if the level of the brake fluid is low, master cylinder failure and/or the hand brake is on (sometimes this is a separate light). This is what I am going to do. Eric
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Peter C in Canberra
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Testing brake failure light

Post by Peter C in Canberra » Mon, 20 Oct 2008, 14:18

As indicated by others in this thread I suspect authorities will not be too pedantic about whether the lamp is tested at 'on' or 'start' so long as it is still tested by the actions that start the car. I think both authorities and the driver would also like to see the light come on if vacuum fails (if used for power brakes). I expect the bulb testing and the vacuum failure will be nicely implemented with the single vacuum switch I have described above.
Peter.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

Peter C in Canberra
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Testing brake failure light

Post by Peter C in Canberra » Tue, 20 Jan 2009, 21:49

I have now installed my brake vacuum pump as mentioned above. The car as a whole in not yet running but this bit is tested at least. I have the MES-DEA pump sold by ZEVA connected to brass T-shaped connector with some rubber tube from an auto shop. It was sold as fuel line rather than vacuum hose but had thicker walls and seemed less likely to collapse under vacuum than the stuff sold as vacuum hose. The T piece carries an vacuum switch, normally closed that opens when the vacuum reaches an adjustable point between 5-15psi. The T piece also connects to the original bit of hose that went between the brake booster and the engine. That piece is important to retain because it has a valve hidden inside. The vacuum switch is wired across the pair of wires between the brake fluid float switch and the brake warning lamp.
I was unsure whether I would need or want a vacuum reservoir. Now I don't think it is needed.
When the key is turned to 'on' the pump runs for several seconds and the brake warning light stays on for most of that time till the vacuum has fallen sufficiently to open the switch. The MES-DEA pump has some deliberate hysteresis so that it doesn't keep switching on and off rapidly. I have found that it turns on for a few seconds every 10-15 minutes if the brakes are not applied and the brake lamp remains off. If I push the brake pedal the pump comes on. The warning lamp only comes on if I repeatedly pump the pedal hard. This suggest that the volume of the brake booster with the pump running will retain sufficient vacuum even for emergency braking. If I disconnect the pump after it has pumped down and don't touch the brake pedal it takes an hour or two for enough vacuum loss to occur to light the warning lamp. This is important because this 'resets' the brake lamp testing function. So, in conclusion, this arrangement retains the original function of the brake warning lamp, provides the function of testing the lamp at startup (at least if the car is unused in the previous hour or so), and shows that the MES-DEA pump does not cycle rapidly even without a vacuum reservoir. Finally, the pump is reasonably quiet.
Peter.
Daihatsu charade conversion 2009-18, iMiEV 2013-2019, Holden Volt 2018-present, on the ACT's 100% renewable electricity. Kona on order.

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Testing brake failure light

Post by evric » Tue, 20 Jan 2009, 23:58

The documentation that comes with the MES-DEA says it can be used with or without the reservoir. I am going to use a 2 litre reservoir with the MES-DEA. Ric
Prius Plug-in Conversion: http://www.evplus.com.au ...Holden Barina EV: http://www.evric.kestar.com.au

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