Ian C Posted March 11, 2002 Share Posted March 11, 2002 Just as I get the hang of the mechanical side, what happens? Bizarre electrical fault. Here is the gen I sent Pete Betts - if any other eletrical wizards wish to chip in, be my guest... The phenomena I'm seeing is: Taking the car from a switched off state - position 1 on the ignition works as expected. Position 2 starts the strangeness. Trying to start the car results in it turning over but nothing else happening. After an attempt, the check engine light will glow dimly. The CAT warning light and airbag light may do the same, and can flicker in brightness. This keeps on happening until I 'discharge' the car. If I switch off the ignition and take the keys out, the check engine, airbag, and CAT lights will still be lit. If I measure the voltage drop between chassis ground and any return (i.e. not +12v) wire on a sensor multiplug (I've tried CAT heat sensor, throttle position sensor, trac position sensor, and an Apexi unit's ground), I get either 7.5v (ignition on) or 6.8v (keys out) until I discharge the car. Discharging the car can be done by (after switching the ignition off) - removing EFI fuse 1, removing EFI main relay, or by grounding out a return terminal to a chassis ground. The fuse or relay can be replaced immediately, there is no discharge period. This, however, only reduces the voltage drop on the return wires to 0.5v, it isn't removed fully. Fuses don't blow. If I ground one of the terminals to the chassis, I hear the ABS relay click a bit. The lights on the dash then change, and one Apexi unit fires up - the other has a blue fit, flickering it's illumination lights. Any clues? Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted March 11, 2002 Share Posted March 11, 2002 Ian, this sounds to me like a bad ground point somewhere. Unfortunately in the Supe there is a lot of them. I think if you consult the Electrical Manual on MKIV.com (or the backup site) there is a diagram that lists where all the earth points are. I do not envy you on this one as these types of faults can be a real bi*ch. Good Luck Quote Link to comment Share on other sites More sharing options...
Branners Posted March 11, 2002 Share Posted March 11, 2002 dont forget the alarm systems are very good at making things play up, you dont happen to have a clifford do you? JB Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted March 11, 2002 Share Posted March 11, 2002 There isn't water in the fuse box is there? Remove the power feeds at source from ALL extra gadgets and see what happens. Check all earths. That's about as far as I can go without having the car here, and even then as electrics are not my forte, i would be for bringing in a decent Sparkie. Quote Link to comment Share on other sites More sharing options...
Guest Mycroft Posted March 12, 2002 Share Posted March 12, 2002 (Edited by Mycroft at 4:39 pm on Mar. 12, 2002) Quote Link to comment Share on other sites More sharing options...
Ring Master Posted March 12, 2002 Share Posted March 12, 2002 While we are on the subject of electrical faults, the "green ring" around the drivers door lock is permanently lit , this causes the battery to flatten after about 3 days. Can anyone suggest a fix ? Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted March 12, 2002 Share Posted March 12, 2002 As sent to Ian...... > Taking the car from a switched off state - position 1 on the > ignition works > as expected. So you can turn the iginition on enough to get the radio and heater/blower to start as normal. >Position 2 starts the strangeness. This is the starting/cranking position right? > If I switch off the ignition and take the keys out, the check engine, > airbag, and CAT lights will still be lit. So sounds like it's still being powered by something. Do you have a turbo timer? What alarm system do you have? Could it be the immobiliser is broken? Does the alarm still work correctly. i.e. if you open the door with he alarm on does it sound off properly? Check all earth points are securely made, clean them if need be. > If I measure the voltage drop between chassis ground and any > return (i.e. > not +12v) wire on a sensor multiplug (I've tried CAT heat > sensor, throttle > position sensor, trac position sensor, and an Apexi unit's > ground), I get > either 7.5v (ignition on) or 6.8v (keys out) until I > discharge the car. This is wierd. Someone else has emailed me to say he has a fault (after trying to fit some equipment to his car) that puts the MAP sensor output to 7.2V and the car fails to start. Turns over, occasionally catches and then dies. Wonder if they are related? > Discharging the car can be done by (after switching the > ignition off) - > removing EFI fuse 1, removing EFI main relay, or by grounding > out a return > terminal to a chassis ground. The fuse or relay can be replaced > immediately, there is no discharge period. So some charge is being stored by something and then discharged when you ground out pretty much any sensor wire (from a pin in the sensor plug I'm assuming) I'm trying to think of how that could happen. Random things now..... Does the interior light come on when it should? Do the headlights work? Do the brake lights work? (I've had someone before have the brake lighting circuit (relays) shorted out which back powered the interior lighting circuit so whenever he pressed the brake pedal the interior lights came on.) The problem is highly likely to be connected to the weather. I think that's a fair assumption as it was fine before then and you did nothing special this time. So if it's weather then it's likely to be water ingress somewhere or enough spray to cause a short in some circuit. Or maybe you can be more specific about that bang you heard whilst driving to your mums. Is there any sign underneath of it being hit by something? Nothing is wedged where it shouldn't be? Are any of your carpets damp? Has water got in anywhere else? > This, however, only reduces the voltage drop on the return > wires to 0.5v, it isn't removed fully. Does it eventually drop to 0V? Given time? Regards Pete Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 12, 2002 Author Share Posted March 12, 2002 Thanks for the response guys, it's cheered me up a bit Martin F - where is the backup site for Mkiv.com? The site is still down. Branners - I'm not sure what alarm system I have. The fact that it was sat for the weekend in an exposed area in the wind and the rain, and has those vents on the bonnet doesn't seem too good! I'll check tonight what make it is. Chris - Do you mean unplug things like the Apexi units, the UFCC, the stereo, sort of thing? The fuse box is dry (on the top) but I think I should look beneath it! With the battery removed, of course... Mycroft - No spare battery, I shall try and blag one from somewhere to try. I do have a spare alternator, though, should it be that - how can I test without surgery? I don't know what a system integration relay is, and there isn't any clicking behind the dash - only the ABS relay when I ground stuff with the ignition on. Ring master - No idea, mate - do the cabin lights go out when the door is shut? Take the bulb out as a temporary measure? And gerroff me thread Pete - Thanks for your help so far, I've mailed you back. As ever, I'll ensure you all get the info I learn from my disasters... -Ian Quote Link to comment Share on other sites More sharing options...
Alex Posted March 12, 2002 Share Posted March 12, 2002 Ian, I'll come over tonight...therefore you'll have a spare battery. (Edited by Alex Holdroyd at 1:51 pm on Mar. 12, 2002) Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted March 12, 2002 Share Posted March 12, 2002 http://mkiv.christurner.net Quote Link to comment Share on other sites More sharing options...
Ian C Posted March 12, 2002 Author Share Posted March 12, 2002 As an update (much condensed from the info I've sent Pete): The voltage drop is 0.54v with everything plumbed in. The following affect it: EFI#1 fuse, +0.06v when removed EFI Main Relay, -0.01v when removed EFI no2 Relay, -0.04v when removed Removing both EFI#1 fuse and the Power fuse causes the voltage to drop to 0.02, then 0.01 a couple of seconds later, then after 30ish seconds it finally stabilises on 0.0v I took the battery out, and began measuring resistances. The sensor output wires had a 70k-ish ohm resistance between it and the positive battery cable (with Power and EFI#1 fuses in place to complete the circuit) The only way I got this to vary was to remove the big cable from the alternator, or just to touch the isolated terminal that it connects to with my fingers... The reading went to infinite (which is, I believe, what it bloody well should be!! Sensor return wire to live shouldn't be happening, should it?!) Removing the 3-way multiplug from the back of the alternator had no effect on the reading. Note - I couldn't get the ALT fuse out of the box - all others have been removed. I have to get medieval on it's ass, as it's plastic casing is brittle and just crumbles when I try to prise it out... Opinions/ideas/suggestions welcome. I know I need to retest with the ALT fuse out... -Ian Quote Link to comment Share on other sites More sharing options...
Guest Mycroft Posted March 13, 2002 Share Posted March 13, 2002 If it is like the Soarer then the Alt fuse IS locked and is done so very cunningly, Ill photograph it tomorrow and try to post it here! I need to look at it to remind myself how it was done, might be of no help though. My friend who owns a Toyota/Lexus franchise thinks that you have a leaking heater matrix and that has damaged and ECU circuit. Have you lost a little fluid from the rad, you wouldn't need much to corrode the wiring with anti-freeze in the water, he did say (like someone on this forum) that just getting to look at it is a bit of a palaver. Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted March 14, 2002 Share Posted March 14, 2002 >If it is like the Soarer then the Alt fuse IS locked and is done so very cunningly It's bolted from underneath of the fuse box in the engine compartment. So no amount of pulling it will remove the Alternator fuse. anyway heres some of my analysis....bits from my conversation with Ian............... > the VSV has a +0.08v on the ground pin, and 0v on the input pin, it > can't be causing this leak. The 0.08V sounds like the ground of the VSV has a long path back to the battery (chassis gnd) and this has a small resistance. Or rather than a 0ohm resistance path to the ground it has some resistance. i.e. the route back to the battery/chassis earth is possibly damaged or has to find an alternative route back to gnd due to it's own normal route being broken. Current is a funny thing. (or maybe you'll hate it after this...) For instance if you say had a box that was powered by 12V and 0V and had an input signal that pulsed (say 0->5V) then with the 12V power off there may be an occasion where the actual input signal can back power the circuit, mainly due to a lot of silicon chips being like a lot of simple diodes and transistors which just route current. If an electron can find a path back to 0V it will do, however long the path is. (actually they flow from -ve to +ve but that's going to confuse you, although conventionally you speak of things flowing from +ve to -ve) > My big question is, how the hell does ground get a positive > voltage on it?! The effect of seeing a voltage is indicative of there being a resistance in the circuit somewhere. For information of how a voltmeter works look at http://www.users.dircon.co.uk/~doctron/meter.htm The key to measuring a potential difference (voltage) is the circuit is not changed: the voltmeter is connected in parallel and voltmeters must have a HIGH resistance. Digital voltmeters use sensitive electronic components to directly measure the voltage difference between two wires. Virtually no current flows between those two wires (high resistance), so that the meter simply makes a measurement of the charge differences on the two wires. It all smacks of the ground being duff. > they 'leak' their supplied > power back to > the battery via the ground, albeit after having done some > work with the > power first. True on a working system but..... imagine you have simple circuit that's powered by 12V and has a return path to 0V through a resitance (the resistance is the black box thing, whatever it does, say the solenoid) Now on a working system the voltage differential is 12V, why? Not just because you have 12V at one end and 0V at the other but because all the current flows through this device and nothingelse gets in it's way. Now imagine that you have an unknown resistance (a red box say, that again does something but you don't know what) connected to what you thought was the 0V point of the black box. Now the whole circuit looks like 12V goes to the power input of the black box, then exits the black box, but hang on...... it's not 0V?????,,,, the exiting power from the black box is entering the unknown red box power input. The power finally leaves the red box and gets back to the battery. (now any electronics person will crucify me for that as it's all in reverse and we are talking current but in laymans terms it's simpler to understand how voltage travels from one place to another) Now remember you thought..... hang on....it's not 0V????..... well that shows that what you thought was connected straight to 0V isn't! There's something mysterious in the way, your unknown red box. The key to this problem is finding this red box. (remember this is just an illustration and you are unlikely to find an actual "thing" (red box) as it's more likely to be a case that the original return path to 0V is broken and it's actually routing through another circuit in the system (hyjacking it if you like) and then back to 0V. Does that make any sense at all? > How do you get a positive voltage on the ground side of the > circuit, when > the battery is in place? I don't understand it! Hope the above helped. > Is it possible for a > battery to do that? No. It's likely to be a bad ground/earth path. > How can a connector that normally goes > straight to > ground have a voltage between it and the ground terminal of > the battery? Because now it's NOT NORMALLY connected STRAIGHT to ground it's been diverted somewhere else. > Boggle. Is it worth trying a differnt battery?! Doubt it. There are many many earthing points within the car and my workshop manual shows them so maybe I can fax you a drawing/page or something? Regards Pete Quote Link to comment Share on other sites More sharing options...
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