Neil A Posted May 29, 2007 Share Posted May 29, 2007 While getting my car MOT'ed today the car started cutting out when the brake pedal was pushed. This continued as I drove away with my fresh MOT certificate, so I popped into Caterham. Damien removed the brake circuit fuse which seemed to do the trick and got me home. He said the switch in the pedal box is the most likely cause. However when I got home, I put the fuse back in and now the engine doesn't cut out. Any ideas? Cheers. Fellas, smoke me a kipper, I'll be blatting for breakfast. Official Puck Buck to the Bracknell Fire Bees. Link to comment Share on other sites More sharing options...
Unclefester Posted May 29, 2007 Share Posted May 29, 2007 Demonic Possession? Lucy in the Sky with Diamonds..ooooh hooo hooo!!... 😬 😬Abbey Road Time-Machine *eek* Link to comment Share on other sites More sharing options...
Tony Whitley Posted May 29, 2007 Share Posted May 29, 2007 A dead short in the brake light circuit bringing the battery voltage down to the point that the engine cuts out But without blowing the brake light fuse Link to comment Share on other sites More sharing options...
w7rren Posted May 29, 2007 Share Posted May 29, 2007 It could be the brake switch that is 'sending' the live feed to an electronic component that doesn't need it. just out of interest try taking the bulb out & see if it still does it. Then report back . Cheers, Mark. Born again sevener Link to comment Share on other sites More sharing options...
Colin Mill Posted May 30, 2007 Share Posted May 30, 2007 One other thing - fuse 1 that serves the brake lights also serves the reversing light. If the problem comes back it could be worth checking if popping into reverse also kills the engine. Since the brake lights worked (or you have a very lenient MoT tester 😬) a short on the brake circuit does not sound likely. I had a headlight problem that was simply one of the relays near the fuse-box trying to drop out. Could be worth giving all the fuses and relays a shove back into place. Link to comment Share on other sites More sharing options...
Neil A Posted May 30, 2007 Author Share Posted May 30, 2007 Brake lights are working ok, but got away with the fog light not working Put the fuse in and drove 20 miles to Guildford with no problem. However on the way back the problem came back, however by the time I found a layby to remove the fuse again, it had started behaving itself again. I have a Catstart fitted. When I press the brake pedal it is not just the engine stalling, but the whole ignition system turning off. If you stall the car normally with Catstart it will still stay in position 2. Fellas, smoke me a kipper, I'll be blatting for breakfast. Official Puck Buck to the Bracknell Fire Bees. Link to comment Share on other sites More sharing options...
Nov-07 Posted May 30, 2007 Share Posted May 30, 2007 Take off the pedal box cover, and examine the split pins, if any, securing the clutch and brake pedals on the shaft. It is possible for the legs of a pin, if not properly folded back round the shaft, to touch the live terminal of the brake switch. This puts a full Earth on the supply. The split pin can rotate in use, so the effect is intermittent. I replaced 3 fuses before I discovered the cause Link to comment Share on other sites More sharing options...
susser Posted May 30, 2007 Share Posted May 30, 2007 Brilliant. Link to comment Share on other sites More sharing options...
Tony Whitley Posted May 30, 2007 Share Posted May 30, 2007 I was right When you have eliminated the impossible, whatever remains, however improbable, must be the truth. Link to comment Share on other sites More sharing options...
Neil A Posted May 31, 2007 Author Share Posted May 31, 2007 Cheers guys. I will take a look and report back. Personally I think Uncle Fester is probably right. Fellas, smoke me a kipper, I'll be blatting for breakfast. Official Puck Buck to the Bracknell Fire Bees. Link to comment Share on other sites More sharing options...
Colin Mill Posted May 31, 2007 Share Posted May 31, 2007 You seem to be the first to get Caterham's top secret micro-hybrid system - it stops the engine OK when you stop they just have to develop the auto re-click, sorry I mean re-start 😬 Link to comment Share on other sites More sharing options...
Neil A Posted June 1, 2007 Author Share Posted June 1, 2007 Well after 4 hours hunched over the bastard it is still doing it. Thought it had spookily gone away, but jumped in to take it for a hoon and cut out as I applied the brake halfway out the garage. Looked in the pedal box. Nothing is near to touching the switch. Took switch apart and all free of corrosion. Deffinately related to the brake light circuit as I get the same results if I touch one of the connections to the R clips on the cutch pedal. Wiring for the brake switch looked rather strained in places where cable ties are done up tight. Undid these and stripped back the tape around them to check the insulation on them, but all looks fine. Any ideas? Fellas, smoke me a kipper, I'll be blatting for breakfast. Official Puck Buck to the Bracknell Fire Bees. Link to comment Share on other sites More sharing options...
andy couchman Posted June 1, 2007 Share Posted June 1, 2007 Brake pedal - is that the one in the middle? Thought that was for emergencies only... Andy Link to comment Share on other sites More sharing options...
millsn Posted June 1, 2007 Share Posted June 1, 2007 Start looking for ECU connections to your brake light circuit. I assume it does it if you pull the fuses to the brake lights Link to comment Share on other sites More sharing options...
Neil A Posted June 1, 2007 Author Share Posted June 1, 2007 If you pull the fuse it solves the problem but you don't have any brake lights. Does the brake light circuit go through the ecu? Fellas, smoke me a kipper, I'll be blatting for breakfast. Official Puck Buck to the Bracknell Fire Bees. Link to comment Share on other sites More sharing options...
w7rren Posted June 2, 2007 Share Posted June 2, 2007 As mentioned before, try removing the brake light bulbs, as an ex auto electrician I have come across an instance when a faulty bulb created havoc by diverting the live where it shouldn't be . Worth a try Cheers, Mark. Link to comment Share on other sites More sharing options...
Colin Mill Posted June 2, 2007 Share Posted June 2, 2007 Hi Neil Since the brake light switch is on the positive side of the brake lights when you are connecting the feed terminal of the switch to the R clip you are shorting the supply out. That should blow the brake light fuse pretty fast but from the sound of it the fuse is surviving this which suggests to me that the current is being limited below that needed to blow the brake light fuse by a poor contact between the fuse box and the battery positive. I don't know what the wiring on the input side of the fuse box is like physically but from the circuit diagram they don't simply bus all the fuses together on the input side (because some of the fuses are fed from unswitched feeds and others from ignition switched feeds). My guess is that either in the ignition switch itself or in the wiring between battery, ignition switch and the fuse box you have a poor contact which is allowing the voltage to drop on several feeds out from the fuse box. It would be very useful to be able to monitor the voltage on the input side of the brake light switch as you apply the brake. My bet is that you will see a drop in the voltage here that is far more than you get when measuring across the battery directly. This would confirm the poor contact in the feed to the switch. Then you will have to trace it back. My guess is that the fuel pump is fed off the same output from the ignition switch and when you put the load of the brake lights on there as well the pump falters enough to kill the engine. Have fun Colin this diagnosis comes to you without warranty, expressed or implied. The recipient is not entitled to any compensation in regards to any failure of the diagnosis and no liability for consequential loss is accepted. However, at the vendors discretion an alternative diagnosis of equal whackiness may be offered in exchange. Any correspondence regarding this diagnosis must include your full bank account details and be addressed to RICHARD UMOOGOO, P.O Box 101, Abuja, Nigeria. Edited by - Colin Mill on 2 Jun 2007 10:50:27 Link to comment Share on other sites More sharing options...
Ray Pearce Posted June 2, 2007 Share Posted June 2, 2007 I believe the clue here is the CatStart resetting itself. When I installed mine I bodged the earth connection and found that any random jolt could cause the CatStart unit to momentarily lose power and turn off the ignition. As you said, any other reason for the engine stopping would leave the ignition on. I would check for any loose connections to the CatStart that could be intermittent under breaking. Link to comment Share on other sites More sharing options...
Colin Mill Posted June 2, 2007 Share Posted June 2, 2007 Interesting point about the CatStart - is that also fed from the same terminal of the ignition as the brake light circuit? If so, it adds weight to the possibility of a problem on the feed side of the fuses. Link to comment Share on other sites More sharing options...
Neil A Posted June 2, 2007 Author Share Posted June 2, 2007 Right off to buy a volt meter then. Did start to remove the light bulbs but got distracted when one of them blew and replaced it. Will try removing them. Cheers for the advice guys. Will return with more info. Fellas, smoke me a kipper, I'll be blatting for breakfast. Official Puck Buck to the Bracknell Fire Bees. Link to comment Share on other sites More sharing options...
Johnty Lyons Posted June 2, 2007 Share Posted June 2, 2007 I would guess that this problem is more acute because of the Catstart installation With the Catstart being processor controlled a dip in the input voltage will cause a change of state ans is similar to a montarty push on the button. I will also wager that you have a problem in the rearlight units with a partial short in the brake light cct or in the multi connectors in the rear wheel arches, this is a common caterham problem and just requires a strip down and carefull inspection and rebuild . A HRD in the brake cct will drop the voltage in the IGN controlled cct and that is killing the Catstart. Proof is disconnect Catstart and revert to original Car will continue to run. Best bit is that without having fitted a Catstart you never would have realised you had a problem So hats of the Chris. jj N.I. L7C AR 🙆🏻 Membership No.3927. Link to comment Share on other sites More sharing options...
Neil A Posted June 4, 2007 Author Share Posted June 4, 2007 Right, posting again as the computor crashed during my last attempt. I have taken the lights off and inspected the wire connectors. The pins look ok, a couple look slightly tarnished, but not bad. How do I clean these up? I can't see how to get them out of the connector. The metal part of the lights themselves are rather corroded, including the area around the earthing point. Could this be the cause? I also tried taking the bulbs out to see if the problem persisted. Unfortunately I could not replicate the problem today. So I forced the issue and shorted the switch on one of the R-Clips in the pedal box. This time it blew the fuse, and the replacement fuse also. Before, it was just cutting the ignition and leaving the fuse intact. After a few minutes of ammusement using my newly aquired voltmeter, I ain't exactly sure what I should be measuring and when. Any advice warmly received. Fellas, smoke me a kipper, I'll be blatting for breakfast. Official Puck Buck to the Bracknell Fire Bees. Link to comment Share on other sites More sharing options...
Colin Mill Posted June 4, 2007 Share Posted June 4, 2007 Hi Neil From what you say about the fuse blowing on shorting the switch terminal to ground it sounds as if the fault is an intermittent poor contact (which makes me wonder about the ignition switch as every time you operate the switch you are breaking and re-making those contacts which would explain why its so variable) Anyway, I would suggest that you set the DVM on the 20 volt range and connect the negative probe to the negative terminal of the battery and the positive probe to the input terminal of the brake light switch (the plain green wire according to the circuit diagram). Note the reading with the ignition on and the brake off and then with the brake on. You should see only a very small difference between these two readings (about 0.1 volts) If the drop is much bigger than this then you know that the feed to the brake circuit is poor. I would try this test several times and turn the ignition switch between tests and see if the drop differs between tests. Assuming you do find an excessive drop then you need to start tracing. If you start at the battery you can check that the volt drop at the battery itself is small when the brake is operated. Then look at the feed to the ignition switch. The brown wire to the switch is an unfused feed so be careful not to short it or any of the other terminals on the ignition switch to ground! Repeat the brake off/on test and see if the brown wire terminal voltage is good. If so then look at the white wire out from the ignition switch (which goes to feed several fuses including fuse 1). If that voltage is still good then the fault must be up near the fuse box. I hope that helps!! Best regards Colin Edited by - Colin Mill on 5 Jun 2007 11:24:56 Link to comment Share on other sites More sharing options...
Neil A Posted June 5, 2007 Author Share Posted June 5, 2007 Right have measured between the Battery negative and the brake switch with the engine running. Brake light off/on I got off / on 13.87V / 13.34V 13.92V / 13.31V 12.93V / 12.53V (Fan came on) On the brown wire in the cabin I have brake off / on 13.98V / 13.93V On the white wire in the cabin I have brake off / on 13.90V / 13.32V Fellas, smoke me a kipper, I'll be blatting for breakfast. Official Puck Buck to the Bracknell Fire Bees. Edited by - Neil A on 5 Jun 2007 14:35:19 Link to comment Share on other sites More sharing options...
Colin Mill Posted June 5, 2007 Share Posted June 5, 2007 Hi Neil A drop of half a volt and over sounds to be on the high side to me (two brake lights at 21W each should pull about 3.5 amps so a drop of 0.5v suggests a source resistance of about 0.14 ohms which is rather a lot for the length of wiring involved). Its not as it stands enough to cause trouble but suggests you should look to locate the cause. If you can easily get onto them I would try testing the voltage at the ignition switch as that is my guess for the source of the problem. Link to comment Share on other sites More sharing options...
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