JST Posted September 29, 2009 Share Posted September 29, 2009 i was looking through theseare they suitable as an engine cut out for a challenge truck vehicle electrics rather than the winches. i am after one with protection for the alternators, but the 2nd one down doesnt look as capable in that it doesnt give any ratings and what ratings would i need? its a diesel if that makes any odds Quote Link to comment Share on other sites More sharing options...
white90 Posted September 29, 2009 Share Posted September 29, 2009 James the one from Peter Lloyd Rallying is the one you want with the resistor to protect the alternators. The second one you picture is the one you want cheaper from http://www.peterlloydrallying.co.uk/index.php?main_page=product_info&cPath=0&products_id=117 Quote Link to comment Share on other sites More sharing options...
JST Posted September 29, 2009 Author Share Posted September 29, 2009 James the one from Peter Lloyd Rallying is the one you want with the Resistor to protect the alternators same as VP one but £4 less Quote Link to comment Share on other sites More sharing options...
white90 Posted September 29, 2009 Share Posted September 29, 2009 http://cgi.ebay.co.uk/FIA-BATTERY-MASTER-CUT-OFF-SWITCH-WESTFIELD-CATERHAM-7_W0QQitemZ400075863533QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item5d266135ed&_trksid=p3286.c0.m14 cheaper and shows the Resistor (white square item) Here is a thread and shows mine: http://forums.lr4x4.com/index.php?showtopic=9207&hl=battery+cut+off Quote Link to comment Share on other sites More sharing options...
mmgemini Posted September 29, 2009 Share Posted September 29, 2009 I'll second an FIA battery master switch, not only as a cut out switch but a security measure as well. Now I know there's more than a few of you on here who compete. So !! Has anybody had problems with the metal bit on the key wearing and causing problems ? I've been told it's a big problem. I've not had a problem in five years with one on my present truck, nor on any rally car ? Oh yes, the other thing I was told, the switch is easily overridable. I haven't managed to do that. Answeres on how by PM please. mike Quote Link to comment Share on other sites More sharing options...
landmannnn Posted September 29, 2009 Share Posted September 29, 2009 The problem I have had with the red key is dropping it in the mud and losing it. You then fairly quickly learn how to override it. Quote Link to comment Share on other sites More sharing options...
Eightpot Posted September 29, 2009 Share Posted September 29, 2009 I fitted the cheaper one at the top of the page - was great till the contacts melted! Quote Link to comment Share on other sites More sharing options...
MJIbex Posted September 29, 2009 Share Posted September 29, 2009 So !! Has anybody had problems with the metal bit on the key wearing and causing problems ? I've been told it's a big problem. I've not had a problem in five years with one on my present truck, nor on any rally car ? I unknowingly swapped keys with a mate (slightly different switch/key) and when hot the circuit kept intermitantly closing. Swapped the key back and the problem disappeared. Mark. Quote Link to comment Share on other sites More sharing options...
p38rr Posted September 29, 2009 Share Posted September 29, 2009 No need to have a fancy switch!! Just put the charge supply from the altenator the battery side of any isolater and this will kill the engine as soon as it is switched off and any charge from the altenators will stil go to the batteries! Quote Link to comment Share on other sites More sharing options...
ltwt1981 Posted September 30, 2009 Share Posted September 30, 2009 This defeats the object of the isolator, which is to kill all power. This is a fail at scrutineering. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted September 30, 2009 Share Posted September 30, 2009 It's a resistor, not a diode. Quote Link to comment Share on other sites More sharing options...
Dave W Posted September 30, 2009 Share Posted September 30, 2009 This defeats the object of the isolator, which is to kill all power. This is a fail at scrutineering. I'd be amazed if a scrutineer would fail this arrangement. Most scrutineers seem unable to accurately measure wheel spacers never mind follow all your wiring to figure out if the alternator power cable is isolated ! the MSA reg simply states that the switch should isolate all circuits. If you want to be pedantic it could be argued that having the alternator power feed connected to the vehicle side of the isolator also doesn't meet this requirement IME the only test I've ever seen done on an isolator switch is to ensure that the engine stops when it's activated. Connecting the alternator to the battery side of the switch passes this test. Quote Link to comment Share on other sites More sharing options...
mmgemini Posted September 30, 2009 Share Posted September 30, 2009 I'd be amazed if a scrutineer would fail this arrangement. Most scrutineers seem unable to accurately measure wheel spacers never mind follow all your wiring to figure out if the alternator power cable is isolated ! the MSA reg simply states that the switch should isolate all circuits. If you want to be pedantic it could be argued that having the alternator power feed connected to the vehicle side of the isolator also doesn't meet this requirement IME the only test I've ever seen done on an isolator switch is to ensure that the engine stops when it's activated. Connecting the alternator to the battery side of the switch passes this test. So if you do that why doesn't the engine run on the alternator power as the alternator is still running ? mike Quote Link to comment Share on other sites More sharing options...
Aragorn Posted September 30, 2009 Share Posted September 30, 2009 Because even if the alternator is running, its on the BATTERY side of the isolator? Therefore the alternator is isolated from the rest of the vehicles electrical systems just like the battery is? The only component that would see power from the alternator with the switch off is the battery? Quote Link to comment Share on other sites More sharing options...
ltwt1981 Posted September 30, 2009 Share Posted September 30, 2009 I've seen race cars wired up this way, and the battery back feeds through the alternator connection to keep it running, that's why the diode system. We start the car and switch off with the isolator it should all stop, I've also seen cars where the engine stops but the lights are still on, or at least the rain light. I admit we can't check all the wiring but we will do our best in limited time. Remember the Blue Book states that it is the competitors responsibility to ensure his vehicle is within the rules as the scrutineer cannot check everything in the limited time available. Individual scrutineers check on different things, so you may well get caught out in the end. It's in your own best interests to get it right, as it's your life on the line in a crash or fire. Quote Link to comment Share on other sites More sharing options...
Mark90 Posted September 30, 2009 Share Posted September 30, 2009 I've seen race cars wired up this way, and the battery back feeds through the alternator connection to keep it running, that's why the diode system. If it's done properly so the only connection from the alternator output goes direct to the battery and the vehicle electrics all run from the non-battery side of the isolator I can't see how the vehicle could run on. It's like saying that the vehicle would run on when you switch the ignotion off because the battery is still connected to the alternator. Also as mentioned it's not a diode it's a load resistor for the alternator to dump any residual 'power' through. Quote Link to comment Share on other sites More sharing options...
Aragorn Posted September 30, 2009 Share Posted September 30, 2009 presumably the other method of bleeding power would be thru the alternator warning light. Usually with the ignition on and the engine running both sides of the bulb are at 12v, no PD, no illumination. If the alternator was producing no output, the alternator side would drop to 0v and current would flow, lighting the bulb. Similarly though if the alternator side was still at 12v, but the other side dropped to 0v because you've just killed the master switch, some power could leak thru the bulb, and MIGHT be enough to keep for instance a stop solenoid on a diesel open. Quote Link to comment Share on other sites More sharing options...
Mark90 Posted September 30, 2009 Share Posted September 30, 2009 . Quote Link to comment Share on other sites More sharing options...
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