paulob1 Posted March 3, 2012 Share Posted March 3, 2012 I am sort of involved with a HHO system manufacturer that reduces emissions on diesel engines and improves fuel consumption, so far only tested inacurately and hence the reason for fitting to the DROPS truck. However the project has identified a few faults on the truck, first the altenator diodes failed and the output dropped to less than 24 volts, this was repaired, however on refitting we now have the oild pressure guage, the temperature guage and the rev counter all instantly moving to full on, ie moving as if at full values, now to our minds this would normally indicate a earth problem but we have checked all the earths and as much of the cable paths as we can and can find no apparent earth fault or broken wire....does anyone have any idea what we may have done to the guages... there is a diode in the back of the intrument panel and this could have failed...anyone any ideas Quote Link to comment Share on other sites More sharing options...
Tony B Posted March 3, 2012 Share Posted March 3, 2012 The diode is a valve, current flows one way. As you say earth short is the first thought. Easy to check diode with multimeter. Most have a diod check on them, if not set on ohms. Current should flow one way, not other. If the diode has a band on it, that (If theold grey is stilll working) is the + end. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 3, 2012 Share Posted March 3, 2012 Paul I have the complete set of DROPS FAESP. Are you going to the Bournemouth Airport do tomorrow? I can bring them & I have a battery reader if you bring a camera to copy what you need. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 3, 2012 Share Posted March 3, 2012 Paul curiosity got the better of me & I looked in the electrical fault finding section but there was nothing covering your fault. Anyway here are the relevant sections of the circuit diagrams. Gauges 18 rev 19 temp 20 oil 21 fuel 22 air 1 23 air 2 24 air 3 Quote Link to comment Share on other sites More sharing options...
Tony B Posted March 3, 2012 Share Posted March 3, 2012 (edited) The bug*r is that the rev counter is completly seperate from the other gauges. From that I'd suspect there must a jnction box wher the wires meet. That's where I'd look for the problem. I'd suggest the 184/181 location. It is the only place that a join shows close and is feeding positive voltages. Edited March 3, 2012 by Tony B Quote Link to comment Share on other sites More sharing options...
paulob1 Posted March 3, 2012 Author Share Posted March 3, 2012 hmm it is as I thought a mix of issues...I think the rev counter must have an issue with the newly fixed alternator, did i mention that...it worked alright before it was fixed but the guages were playing up prior to the alternator being replaced.../repaired..have an auto electrician coming monday. I was goping to come clive, i was going to bring the daf with the FH77 and a saracen, was going to then leave them at the muesuem to add to their collection...but cant drive it wihout the rev counter the oil guage and temperature guage not working,...would have me worried all the way...also going to drop off a Star 660 and maybe a zil 131 truck too. not sure how many they can take but i think a few military vehicles will add to the sites interst level... Quote Link to comment Share on other sites More sharing options...
fv1609 Posted March 3, 2012 Share Posted March 3, 2012 That's a shame Paul to have it go wrong of all weekends. Do you have any of the DROPS AESPs ? I think I have the complete set which includes fault finding & parts list, 19 sheets of FAESP. Quote Link to comment Share on other sites More sharing options...
01ec28 Posted March 4, 2012 Share Posted March 4, 2012 difficult to read the legend on the photo, but am I correct in believing that you have three wire guages? positive, negative, and then variable resistance senders? If so do you have a ground reference still at point 5? Sounds like one leg is gone (open) if they're three wire system. Quote Link to comment Share on other sites More sharing options...
Bran D Posted March 4, 2012 Share Posted March 4, 2012 Power supply to the cab comes onto 2 studs located below the passenger glovebox, just to the left of it. I had several dodgy earths, so remade all these and things were a lot better. the Rev counter is run form a seperate alternator output, so may be connected with having the alternator repalced. The tacho interface is mouted below the fuses and relays. Good luck Quote Link to comment Share on other sites More sharing options...
Tony B Posted March 4, 2012 Share Posted March 4, 2012 The obvious for the rev counter is- 'You have put the right wire in the right place?' Quote Link to comment Share on other sites More sharing options...
paulob1 Posted March 4, 2012 Author Share Posted March 4, 2012 That's a shame Paul to have it go wrong of all weekends. Do you have any of the DROPS AESPs ? I think I have the complete set which includes fault finding & parts list, 19 sheets of FAESP. no I have the full parts manual but that is it...could do with the full set of everything but not found them yet...are yours for sale or can you copy for me for a price... Quote Link to comment Share on other sites More sharing options...
paulob1 Posted March 4, 2012 Author Share Posted March 4, 2012 Power supply to the cab comes onto 2 studs located below the passenger glovebox, just to the left of it. I had several dodgy earths, so remade all these and things were a lot better. the Rev counter is run form a seperate alternator output, so may be connected with having the alternator repalced. The tacho interface is mouted below the fuses and relays. Good luck the alternator repair guy said it had been wired in a very odd way inside, i am just wondering if that odd way was the correct way for the truck...anyway he is coming to have a look tomorrow...your comments all help but i have to suspect disturbed or broken wires when they have been fitting the HHO system... Quote Link to comment Share on other sites More sharing options...
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