Jake Posted February 12, 2004 Share Posted February 12, 2004 Where do you start with electrical problems? My speedo has packed up. It used to go a bit haywire sometimes immediately after I turned the engine off, it would go to Zero then the needle would go up to 70 or 80 MPH and then back to Zero after a few seconds. The other day I was driving quite fast on the motorway and hit fuel cut, at that very moment the speedo stopped working altogether and hasn't worked since. I've had all the dash apart looking for loose connections but couldn't find any. I remade the soldered joints to the TRL Digital Speedo Converter but it's still not working. Also, I don't know if it's related but my car alarm keeps going of for no apparent reason. Usually at 2am! Any suggestions? Thanks Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 12, 2004 Share Posted February 12, 2004 You start off with a circuit diagram or two taken off mkiv.com and find the speedo system. Then you start measuring voltages at various points from the speedo backwards. If the speedo signal pin on the multiplug that goes into the back of the gauge pod doesn't read a voltage, keep tracking back via the electrical schematics to junction points, earth points, the ECU pin that supplies the signal, the TRL delimiter etc, and eventually you should find a voltage. That will tell you where on the circuit the signal is being dropped, making your troubleshooting a lot easier. It's a long job and usually uncomfortable. -Ian Quote Link to comment Share on other sites More sharing options...
Jake Posted February 12, 2004 Author Share Posted February 12, 2004 Sounds like a right PitA. Thanks for the reply. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 12, 2004 Share Posted February 12, 2004 No prob. In fact, as I've done worse than this before and I have a lot of the info to hand, try this for size: Gauge pod circuit: http://www.mkiv.com/manual/1995_electrical_manual/I/95elec_220.JPG http://www.mkiv.com/manual/1995_electrical_manual/I/95elec_221.JPG http://www.mkiv.com/manual/1995_electrical_manual/I/95elec_222.JPG - "speed" http://www.mkiv.com/manual/1995_electrical_manual/I/95elec_223.JPG Looks like the primary power comes in on pin 9B, Yellow. This goes straight to the speedo and also branches off to other parts of the gauge pod. Can't be this that's shafted or else the water & fuel gauge would stop working too, as well as numerous warning lights. The fuel gauge and the rev counter both branch off the speedo's 10B connection (Red) so if they work, it's not the red wire or anything connected beyond that. That leaves the Blue-Red wire of 11B. Now, the vehicle speed sensor is plumbed into that via junction I14 and then connector II1. Output of the speed sensor - part V10, pin 3, at the gearbox: http://mkiv.com/manual/1995_electrical_manual/G/95elec_025.JPG Junction splice point I14 http://mkiv.com/manual/1995_electrical_manual/G/95elec_038.JPG (bottom of page) Connection block II1 http://mkiv.com/manual/1995_electrical_manual/G/95elec_038.JPG (top of page) You'll see that is passenger footwell, under the dash/glovebox - told you it would be uncomfortable http://mkiv.com/manual/1995_electrical_manual/G/95elec_039.JPG gives the pinouts positions, you are looking for pin 2 This blue and red wire also goes off to the odo and trip module but I can't tell from the schematics what it does with it, works out the mileage I guess. So, I reckon if you check the speed sensor output, the II1 connector block, and anything wired onto that blue and red wire, you should come up with your culprit. Don't forget to check for continuity as well as voltage. -Ian Quote Link to comment Share on other sites More sharing options...
Jake Posted February 12, 2004 Author Share Posted February 12, 2004 Wow, thanks! Looks like my weekend is sorted out then. One thing, "check for continuity as well as voltage". What do you mean by continuity? Quote Link to comment Share on other sites More sharing options...
SkyJawa Posted February 12, 2004 Share Posted February 12, 2004 Sounds like a similar prob someone else on here had a while ago, think that was down to a dodgy speed delimiter/converter thingy Might be worth checking?!?!! Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted February 12, 2004 Share Posted February 12, 2004 Might be worth asking me? The designer of them. What version is it? Does it have a software version number on it? The very early ones had this type of problem. Since then I rarely get any problems. If you can find out any details of when you purchased it or who you purchased the car off that would help. I'm willing to help out with a replacement unit. The others will vouch that my converters are good. Certainly a lot better than most out there. Do you know who installed it? [email protected] [email protected] 01676 535888 Regards Pete Quote Link to comment Share on other sites More sharing options...
Jake Posted February 12, 2004 Author Share Posted February 12, 2004 Originally posted by TRL Performance Might be worth asking me? The designer of them. What version is it? Does it have a software version number on it? The very early ones had this type of problem. Since then I rarely get any problems. If you can find out any details of when you purchased it or who you purchased the car off that would help. I'm willing to help out with a replacement unit. The others will vouch that my converters are good. Certainly a lot better than most out there. Do you know who installed it? Hi Pete I hope you don't think that I'm suggesting that it's a problem with the TRL DSC? That wasn't my intention at all. I don't know what version it is without stripping the dash down again. It did have a number written on it in marker pen but I forget what that number was. I purchased it from you in, I think, April last year. I installed it myself. To be honest Pete I don't think the DSC is the problem anyway. I suppose I could easily test it by removing it and seeing if the problems go away. Thanks for the offer of a replacement though. It's much appreciated. Quote Link to comment Share on other sites More sharing options...
THOR Racing Posted February 12, 2004 Share Posted February 12, 2004 No problem. I'm more than happy to send a replacement for you to try. I want a reputation for quality goods and service so will help all I can. Regards Pete Quote Link to comment Share on other sites More sharing options...
Jake Posted February 12, 2004 Author Share Posted February 12, 2004 Originally posted by TRL Performance No problem. I'm more than happy to send a replacement for you to try. I want a reputation for quality goods and service so will help all I can. You've already got that reputation on this BBS. I'll do a little more investigation before I trouble you for a replacemnt though. Thanks for the offer. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 12, 2004 Share Posted February 12, 2004 Originally posted by Jake Wow, thanks! Looks like my weekend is sorted out then. One thing, "check for continuity as well as voltage". What do you mean by continuity? Stick your multimeter on to measure resistance, put one probe on say pin 11B on the gauge pod and the other on pin 3 of the speed sensor and it should read a very low ohms value. If it reads infinite (-1) then there is no continuity between those points, i.e. the wire has broken/become disconnected somehow, and there's your problem right there. In fact, checking for continuity should be job 1, then check for signals. So, God, I've helped someone else out a lot, how about giving me some inspiration with my bastard car's running problems, hmmm? -Ian Quote Link to comment Share on other sites More sharing options...
Jake Posted February 12, 2004 Author Share Posted February 12, 2004 Gotcha. Thanks Ian Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted February 13, 2004 Share Posted February 13, 2004 Originally posted by Jake I suppose I could easily test it by removing it and seeing if the problems go away. That's what I was going to suggest... Ian, love the small print! Quote Link to comment Share on other sites More sharing options...
SkyJawa Posted February 13, 2004 Share Posted February 13, 2004 Pete, Wasn't suggesting your kit was dodgy either, if thats the impression you got? I didn't know Jake had your DSC fitted, but the problem sounded similar to another I'd read about hence my comment, but that was another variety, not yours! As Jake said, I don't think you have a problem with members on this bbs with your service/reputation Quote Link to comment Share on other sites More sharing options...
Jake Posted February 13, 2004 Author Share Posted February 13, 2004 This session of the Pete Betts Fan Club is now adjourned. Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 14, 2004 Share Posted February 14, 2004 Jake, you will let us know what you find out won't you? -Ian Quote Link to comment Share on other sites More sharing options...
Jake Posted February 14, 2004 Author Share Posted February 14, 2004 Originally posted by Ian C Jake, you will let us know what you find out won't you? It's the DSC. I disconnected it from the Speedos Blue/Red wire then rejoined the wire to itself and now the speedo is working again. Pete: It says "V37" in marker pen on the label on the DSC unit. I assume that is the Version Number. Quote Link to comment Share on other sites More sharing options...
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