Testing brake failure light

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drowe67
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Testing brake failure light

Post by drowe67 » Wed, 08 Oct 2008, 13:56

Hi,

In the SA version of NCOP14 it states:

"The vehicle must continue to comply with the design rule requirement that vehicles have a brake failure warning lamp that can be tested by turning the ignition to the start position."

Since the EV conversion my brake light no longer comes on when I turn to start. Could anyone please tell me how this usually works in an ICE system? I am guessing some sort of path to ground via the ICE starter motor is set up, as my brake fluid sensor "fires" when it gets grounded.

I have a few ideas with relays/transistors but would appreciate your thoughts. Maybe there is a very simple way to do this. It's all on the 12V system.

Thanks in advance,

David
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Testing brake failure light

Post by a4x4kiwi » Wed, 08 Oct 2008, 21:27

Hi,

I was just going over the wiring diagram for the hilux. The light test signals work through the alternator charge light circuit (using diode logic). The lights all go out when the engine starts.

You might need to emulate the charge light using a monostable timer. (555 would probably do it.

You will probably need the vehicle schematic to work it out.

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Testing brake failure light

Post by drowe67 » Thu, 09 Oct 2008, 20:11

OK so I worked out a solution with a little transistor circuit, comprising 1 BC547 transistor and a 1k resistor. I found the signal that goes to 12V when the key is turned to start, and worked out that the brake fluid sensor fires by connecting the sensor lead to vehicle chassis. So I rigged something like this:

Image

starter 12V signal - 1k - base
brake sensor - collector
vehicle ground - emitter

Works nicely. I put the little circuit in some heat shrink and taped it to the 12V wiring loom near the brake master cylinder.

Cheers,

David
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Testing brake failure light

Post by acmotor » Fri, 10 Oct 2008, 03:31

Drowe67,

You must read regs differently to me. I took it that the lamp in dash board must be tested (normal lamp test idea) when the ign is switched on, not actuallty when it is moved to the starter motor position ?
This is the way vehicles seem to function i.e. turn ign on and all lamps on the dashboard light and then either go out a few seconds later or in the case of the brake warning light, stays on until the ICE motor has started.

In the case of an EV, I would maybe accept you solution, but ask, what other function has the starter motor position have in your EV ? A driver would not have the test 'in their face' unless they knew that they had to use the starter motor position (that they would not normally use in an EV.)

BTW the starter motor position in my EV is used as a pulse start signal to the Danfoss controller via the zero accelerator position switch. This means you cannot start the controller with foot down.
The effect is similar to the high throttle position logic on some DC controllers. Image
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Testing brake failure light

Post by tdean » Fri, 10 Oct 2008, 06:23

The brake failure warning light is normally out when the engine is running so the reason for seeing the light before a person starts an engine is to indicate that the bulb itself is operational, nothing more. Some early model vehicles do ground the lamp to test it via the start position of the switch but they usually had a separate circuit inside the switch. You can use an ohm meter (I prefer a LED test probe) to check the original switch or if you consult a decent wiring diagram you can work it out easily enough.

The light that we normally call an ignition light is an excitation circuit for the charging system (alternator). Everyone calls it an ignition light and it does come on with the ignition system but it's traditionally been there for the alternator. There are several variations on how this light is extinguished but in pre-ECU days most ign/alt lamps went off once the voltage built up enough from the alternator to equalise the 12volts being fed from the ignition switch. Charging systems do vary and the ignition or alternator lamp (sometimes depicting a battery symbol)is not always connected directly to the D+ field excitation of the alternator.
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Testing brake failure light

Post by tdean » Fri, 10 Oct 2008, 06:34

drowe67 wrote: OK so I worked out a solution with a little transistor circuit, comprising 1 BC547 transistor and a 1k resistor. I found the signal that goes to 12V when the key is turned to start, and worked out that the brake fluid sensor fires by connecting the sensor lead to vehicle chassis. So I rigged something like this:

Image

starter 12V signal - 1k - base
brake sensor - collector
vehicle ground - emitter

Works nicely. I put the little circuit in some heat shrink and taped it to the 12V wiring loom near the brake master cylinder.

David

What happens when the brake failure switch is activated?

I would have used a 5pin automotive relay, a bit easier to replace (or bypass) & looks better. But if that works, hey what do I know?
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Testing brake failure light

Post by drowe67 » Fri, 10 Oct 2008, 14:31

OK, good comments guys, here is take 2:

Image
Image

Don't worry about the looks Terry - it's prettier when it's inside the heat shrink, costs less than an automotive relay too.

This version switches on the brake light when the ignition key is switched to the "on" position, the brake light then fades out after 1 second. So it achieves the aim of testing the brake light every time the car is switched on.

The brake sensor is activated by a float, I couldn't test that directly without making a mess with brake fluid, but by jumpering across the brake sensor line to chassis I tested that the brake light went on.

Despite violating the strict wording of the SA NCOP14 equivalent (Information Bulletin 14) I agree that testing the brake bulb every time the vehicle is used was the intention. The "start" position of my ignition is never used so no point testing the brake light there.

Cheers,

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Testing brake failure light

Post by acmotor » Fri, 10 Oct 2008, 16:47

Well done David.Image Some would have used an intel quad core !Image

I think you have satisfied ADR35 on the lamp test as referred to in NCOP14.... If fact in a superior way to some vehicles where you cannot check the brake fluid sensor without the ICE running !
I am certain that others will find this useful as we all have to comply with ADR35 lamp test. Don't we !Image

The wording 'start' seems quite wrong in the NCOP14 /ADR35. The idea is correct but most ign switches have off, acc, on, start(momentary action for starter motor) and the lamp test is surely to occur in the 'on' not 'start' position. Ok it is all in the wording !

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Testing brake failure light

Post by tdean » Fri, 10 Oct 2008, 18:58

I've just talked to a guy at the Vehicle Inspection Office, Kateena Street, Regency Park SA and he informs me that the brake failure light operation has to conform with the Aus compliance standards for the vehicle. His words were, "...it will comply with the compliance standards". Some systems work by turning the ignition switch to the start position others may be controlled by an electronic module that may turn the light on for 10 secs before going off in the ignition position. In a nutshell if it works a certain way before you convert the ICE to an EV, it has to work the same way, after the conversion to meet compliance.

He tells me they do test the brake failure lamp by shorting out the switch/sensor. Also not all switches/sensors are located in the fluid reservoir, they can be in other locations such as a brake line further down the vehicle.

He's also posting me the SA requirements for "Electric Conversions" so that'll be a good read.
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Testing brake failure light

Post by Peter C in Canberra » Fri, 10 Oct 2008, 22:24

I have just put my dashboard back together and have just noticed my brake light doesn't come on. So here are my first thoughts: Wouldn't this work: Put a capacitor and high ohm resistance parallel to the brake fluid float switch. At turn on, 12V appears across the brake lamp and it lights then fades as the cap charges. When you turn off the resistor slowly discharges the cap so it is ready to again take some current for a short time at the next start. [Or you could use a quad core as suggested.]
Having said all that I think my switch has a connection to the vacuum from the ICE motor so I have to work out what that was doing.....
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Testing brake failure light

Post by drowe67 » Fri, 10 Oct 2008, 22:35

Hi Peter,

That may work Peter, but the low resistance of the lamp will mean you need a large capacitor. BTW what you describe is roughly what the circuit above does; it charges through the 1k resistor and uses the transistor to provide enough current gain to drive the lamp. The 10k discharges the capacitor when the car is powered down.

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Testing brake failure light

Post by BjBlaster » Fri, 10 Oct 2008, 23:59

.
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Testing brake failure light

Post by Peter C in Canberra » Sun, 12 Oct 2008, 03:07

I did some guestimates about the size of cap I would need for the one cap and resistor suggestion above with the lamp in my particular car. Unfortunately it would take about a half Farad cap to keep the lamp on and fading over a second or two.
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Testing brake failure light

Post by Peter C in Canberra » Sun, 12 Oct 2008, 14:29

After sleeping on it I had another idea. Among the salvage from the ICE are various vacuum switches. If I can find a normally closed switch that is opened by vacuum I could place that across the brake fluid float switch. When the car key is turned to start the vacuum switch will bypass the float switch and the brake light will come on. Then as the vacuum pump produces some vacuum the vacuum switch will open and the brake light will go out. I would now have a superior brake warning lamp because the light will come on while driving if I have lost either brake fluid or vacuum. I'm off now to look through the ICE salvage; there were some gadgets that I thought were simple vacuum operated switches. Hopefully they operate the right way, IE normally closed rather than normally open.
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Testing brake failure light

Post by acmotor » Sun, 12 Oct 2008, 16:24

Good idea. Image
But I don't have power brakes. Image

Doesn't NCOP14 require a 'brake fail' indication if the vacuum fails ?
Along the line of your suggestion.
It is part of ADR35.
So you are on to it.

Remember to post full details and pics when you have it working.
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Testing brake failure light

Post by Peter C in Canberra » Mon, 13 Oct 2008, 21:26

Continuing on from above..... none of the various bits of salvage with electrical and vacuum connections had the right characteristics. A someone pointed out in an earlier thread there is a vacuum switch available from evparts in America (www.evparts.com/prod-BK2785.htm). This has a fixed vacuum strength at which it switches (18-22"Hg) and the pump I intend to use is rated at 19"Hg (https://www.zeva.com.au/store.php?product=84). Therefore the evparts switch might not work well for the purpose of shorting the float switch briefly at start up and in the event of a significant vacuum loss; the brake lamp could end up flicking on and off when nothing is wrong with this switch. However, I found a local supplier of a switch that should be suitable (http://www.baccara.com.au/pdf/pmva.pdf). I have ordered the version that is adjustable from 5" to 15"Hg, normally closed SPST, spade connector which was in stock. I ordered over the phone and the cost was $70.40 including GST and postage from Melbourne to Canberra. This appeals more than the suggested circuit because it will kill two birds with one stone, the brake lamp will light whenever the car is started with a low vacuum and it also provides a vacuum failure indication with the same lamp. The only problem I can think of would occur if the vacuum system is so airtight that the vacuum is held long after the car is stopped; that seems unlikely and arranging a slow leak should not be hard!
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Testing brake failure light

Post by tdean » Thu, 16 Oct 2008, 19:17

drowe67 wrote: Hi,

In the SA version of NCOP14 it states:

"The vehicle must continue to comply with the design rule requirement that vehicles have a brake failure warning lamp that can be tested by turning the ignition to the start position."
We must have the same document David. I think this statement should be put into context with the rest of the document by adding the following:

"Australian Design Rules

Converted vehicles must meet the same design and safety requirements that applied to the original vehicle when it was manufactured. Where any system governed by an Australian Design Rule (ADR) is altered, it is necessary to show that the original requirements of the rule, or a later requirement, are still met.

Braking systems (ADRs 31/… and 35/…) – large increases in vehicle mass, alteration of the centre of gravity and/or removal of the normal vacuum or compressed air source will affect compliance with these rules and it is essential that braking performance be maintained within the limits set out by these rules. The addition of a secondary source of vacuum or compressed air will usually be required. The vehicle must continue to comply with the design rule requirement that vehicles have a brake failure warning lamp that can be tested by turning the ignition switch to the “start” position."

So my take on the subject would be that you must know how the original brake failure warning lamp circuit in your vehicle worked before the conversion and how the conversion is likely to affect that circuit.

regards,

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Testing brake failure light

Post by Johny » Thu, 16 Oct 2008, 20:06

The consensus here is the most cars turn on the the warning lights when the ignition is turned on, then turn them off when the engine is started.

From that, there appears to be a contradiction in that existing cars do not 'test' the brake lamp while in the start position (anyone have comments here). Doing the test in the start position is by far the easiest - a small relay with the coil running off the start switch position and the NO (Normally Open) contacts across the brake fail switch.

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Testing brake failure light

Post by tdean » Fri, 17 Oct 2008, 03:15

This diagram is from the GM service manual for my VN Commodore, hopefully it'll be clear enough to read. The brake failure switch (SS1) is tested in the start position(50) via the R65 start relay. When the R52 lamp check relay is activated it not only grounds the brake failure warning lamp, it also signals the B2 terminal in the engine management computer that the engine is cranking (you can't see that circuit in this image).
Image
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Testing brake failure light

Post by drowe67 » Fri, 17 Oct 2008, 23:47

I had my inspection today, I don't think they checked the brake warning light, although I gave them some documentation that explained it comes on when the ignition is switched to the "on" position. It wasn't mentioned or commented on during the inspection.

They have, however, asked for an engineers report to certify that the power source and capacity of the braking system is sufficient and meets all legal requirements. Need to work out what these requirements are, I guess it means maintaining sufficient vacuum over some sort of braking test.

I think a lot of these finer points depend on who does the inspection on the day......

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Testing brake failure light

Post by drowe67 » Sat, 18 Oct 2008, 00:17

I was just perusing ADR31. As you do. Noticed this clause:

5.2.21. Brake failure and defect warning signals (general requirements):

yada yada....

5.2.21.4. The warning signal(s) mentioned above shall light up when the electrical equipment of the vehicle (and the braking system) is energised. <snip>

Note 5.2.21.4 says "energised", not ignition switched to "start" or "on". Thus sayeth the ADR.....

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Testing brake failure light

Post by tdean » Sun, 19 Oct 2008, 01:59

True and the Third Edition of ADR35 says:

35.2.1.2.3. As a check of function the ‘Visible Indicator’ shall be so designed that it operates when:

35.2.1.2.3.1. the ignition or electrical control switch is turned from the “engine off” position to the “engine on” position, and the engine is not operating, and (unless a failure of the type described in clause
35.2.1.2.1 exists in the brake system, or in the event of an electrical failure of the ‘Antilock System’) it shall not operate when the engine is running;

35.2.1.2.3.2. the ignition or electrical control switch is in the “engine start” position,and (unless a failure of the type described in clause 35.2.1.2.1 exists in the brake system, or in the event of an electrical failure of the ‘Antilock System’) it shall not operate after the return of the ignition or electrical control switch to the “engine on” position;

<snipped here due to length of long list of other conditions>

Again it depends on which vehicle model we are talking about here. I forgot to mention another obvious brake failure system, ABS anti-locking have a brake failure lamp that goes out once the ECU has done a system check and the vehicle is moving.

BTW congrats on getting your inspection done.
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Testing brake failure light

Post by drowe67 » Sun, 19 Oct 2008, 12:10

Thanks Terry.

BTW is ADR 35 just for commercial vehicles, the title is "Commercial Vehicle Brake Systems"? ADR 31 has the title "Brake Systems for Passenger Cars"

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Testing brake failure light

Post by tdean » Sun, 19 Oct 2008, 20:45

David, I think it depends on the year of the passenger vehicle.

ADR 31
2.3. This standard is binding on all new model MA and LEP category vehicles from 1 January 2004 and from 1 January 2006 for all vehicles in those categories

2.4. For MB and MC category vehicles, manufacturers can choose to comply with this national standard in lieu of ADR 35/….

ADR 31 applies to MA category passenger vehicles manufactured after 1 Jan 2004 so my 1990 Commodore would use ADR 35, I think thats right, please correct me if I'm wrong.

To add more confusion, this excerpt from "Conversion to Electric Drive":

Australian Design Rules
A modified vehicle is required by law to continue to comply with the Australian Design Rules to which it was originally constructed (or later versions), except as allowed for in the Road Traffic (Vehicle Standards) Rules 1999. A brief description of each ADR mentioned in this bulletin is contained in this appendix.

The ADRs are contained in a number of volumes known as editions. Currently there are two editions in operation:
  • the Australian Design Rules for Motor Vehicle Safety (Second Edition) covering vehicles manufactured on or after 1 January 1969 to 30 June 1988
  • the Australian Design Rules for Vehicles and Trailers (Third Edition) covering vehicles manufactured on or after 1 July 1988.
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Testing brake failure light

Post by drowe67 » Sun, 19 Oct 2008, 23:20

Hi Terry,

Hmmm, good point.

Clause 2.3 says ADR31 is binding for vehicles after 2004. Read with clause 2.4 this may mean that either ADR 31 or ADR 35 can be applied, i.e. it suggests that ADR31 may be applied to pre-2004 vehicles at your discretion.

I get the feeling that the current ADR 31 has replaced some older versions (there is some reference to repealing earlier standards earlier in ADR 31) that dealt with earlier passenger cars.

But I have to say it's a bit muddy to me.

I need to contact a company CPE Monday to get some analysis done on my braking system, so I will ask them what standard applies to us. I suspect as far as we are concerned, they are pretty close.

Cheers,

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