 | Home > Technical > td5 rev counter |
 
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| Clive Member Since: 21 Mar 2014 Location: Littleborough Posts: 467   
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It's not too difficult really, helps if you can solder though. On mine, I just stripped off about 6mm of the insulation on the yellow/pink wire somewhere near the middle of the accessible bit, then wrapped the stripped end of the white/black one around it and soldered it to make it secure, then wrapped it in tape.
I daresay someone else may be along soon enough with alternative ways to connect it, but so long as it's secure and properly insulated then it will be fine. Good luck  |
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6th Aug 2018 6:13pm |
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| GerardTd5 Member Since: 03 Aug 2016 Location: almost Germany Posts: 44  
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I will try and let you know if it has succeeded. Thanks again.
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6th Aug 2018 6:44pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6605 
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It would be here (arrowed), WHITE and SLATE (WS), position 14 (on the end).
 Click image to enlarge Annoying the YELLOW and PINK (YK) colour is indeed used twice, once for the engine speed for the ABS ecu (black ECU plug pin 19 - also used for rev counter) and for the road speed sent from the speedo head to the engine ECU on black plug pin 13). It's not the same signal. 1988 90 Td5 NAS soft top
2015 D90 XS SW |
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9th Aug 2018 2:23pm |
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| GerardTd5 Member Since: 03 Aug 2016 Location: almost Germany Posts: 44
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Hi there,
Yesterday made a start with fitting the rev counter: pink / yellow wire of pin 19 bald and the black / white wire soldered to it. Black / white wire through the bulkhead behind the instrument panel. Green wire from the tachometer connected to the green / white wire of the fuel gauge, it runs through the ignition and black wire connected to the black earth wire of the fuel gauge. Finally, the red / white wire is connected to the illumination wire. The illumination of all gauges works ..... 
When I start the engine, the pointer of the rev counter goes to 5000 rpm and then drops to 0 and does not do anything anymore. 
The earth wire is good, otherwise the illumination did not work either, on the green / white wire of the fuel gauge there is also tension, the black / white wire from pin 19 to the rev counter has not been interrupted or damaged either. What have I done wrong and who has the solution? Thanks in advance, GerardTd5 |
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9th Aug 2018 2:24pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6605
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The Td5 ABS system has a separate ECU so the rev signal doesn't go to the modulator block, it goes to the ABS ECU. 1988 90 Td5 NAS soft top
2015 D90 XS SW |
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9th Aug 2018 2:25pm |
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| Clive Member Since: 21 Mar 2014 Location: Littleborough Posts: 467
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The tacho needle going to 5000rpm and back is normal, part of a "self-check" I guess. If it does nothing after that, then either the tacho signal is missing, maybe connected wrong, or perhaps the white/black wire is damaged and shorting to the body/chassis somewhere. If basic visual checks cannot resolve it you need to get a test meter on the job to see where it's going wrong. |
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9th Aug 2018 9:03pm |
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| LandymanStefan Member Since: 30 Aug 2017 Location: Surrey Posts: 881  
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Just connected mine and it doesn't work. It too wakes up and goes to 5000 and parks back at 0 when it starts. I checked the resistance on the cable from the plug behind the dash to the ecu plug and it returned as 0.0 ohms so a perfect circuit and I checked the new terminal that I installed to the binnacle plug to the rev counter and that was a perfect connection too.
Any ideas 🤔 |
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10th Aug 2018 5:16pm |
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| GerardTd5 Member Since: 03 Aug 2016 Location: almost Germany Posts: 44
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Yesterday morning checked everything and still no working rev counter. On the way to a friend who has more knowledge of electronics than me, suddenly a working rev counter
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Drove back home and quickly made a movie. Joy was short-lived, rev counter stopped it again. 
Instrument panel unscrewed again and by coincidence I found out that if I move the connector of the rev counter back and forth or up and down, the rev counter does it or does not. The cause seems to be in the connector or in the worst case in the rev counter itself. Possibly bad or loose contact in the rev counter, I can hardly imagine. While driving, the needle of the tachometer suddenly falls back to zero, then to indicate 2000 rpm and so on. Today I have no time, tomorrow or Monday I will try again and otherwise I ask the supplier for a new cable harness with connector. The connections of pin 19 to the rev counter, the 12 v of the green / white and the earth cable of the fuel gauge are correctly connected, there is voltage. It should work this way. |
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11th Aug 2018 9:10am |
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| LandymanStefan Member Since: 30 Aug 2017 Location: Surrey Posts: 881
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How irritating, I'll have to give all my connections a wiggle and give the tacho a 'technical tap' and see if I get any life. Thanks for the update.
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11th Aug 2018 9:13am |
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| LandymanStefan Member Since: 30 Aug 2017 Location: Surrey Posts: 881
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So today I've had a bit more time to fiddle ive checked the continuity from the connector which goes to the tacho right the way to the ecu plug and it's fine 0.1ohms resistance.
When I ordered the tacho I ordered two in case a friend or someone I knew wanted one in the future so I plugged that one in today and it is exactly the same, starts up, self checks and goes back to 0 also lights up fine. I feel the only thing I need to know now is if the pulse from the ecu is correct which would confirm if it's the gauges are part of a faulty batch or if our ecus aren't outputting the signal correctly. Is there a way I can check the pin 19 signal? My car is also a 2001 like gerrardtd5's although mine doesn't have abs |
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12th Aug 2018 11:02am |
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| Clive Member Since: 21 Mar 2014 Location: Littleborough Posts: 467
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The "pulse" from the ECU is a continuous square wave of 12 volts Peak to Peak with the frequency dependent on engine speed, it's 24Hz at tickover, (about 750 RPM.) The waveform below was taken directly from the ECU pin 19 connection.
On a normal multimeter you would just see a continuous 6 volts DC on this connection with the engine running, you would need a meter with frequency readout to make any more sense of it, however, if you're getting 6V here rather than zero or 12V, you are at least heading in the right direction. Click image to enlarge |
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12th Aug 2018 11:59am |
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| GerardTd5 Member Since: 03 Aug 2016 Location: almost Germany Posts: 44
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Just to show that it worked. Rev counter is no longer oblique .... I'm trying to upload a movie
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12th Aug 2018 12:49pm |
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| GerardTd5 Member Since: 03 Aug 2016 Location: almost Germany Posts: 44
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File is too large, photo attached
Click image to enlarge |
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12th Aug 2018 12:57pm |
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| LandymanStefan Member Since: 30 Aug 2017 Location: Surrey Posts: 881
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Just stuck a meter on the pin 19 output to the black ground. I'm getting 0.2v, when I put my foot down the numbers bounce about a bit and it can go to 0.3 so clearly not enough to be the proper signal.
I remember years ago my dad had a smart car and he fitted the genuine tacho to it and it had a same problem and he had to take it to a specialist to program the ecu to output its signal to the tacho. I'm wondering if this is a feature that can be enabled/disabled in the ecu? |
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12th Aug 2018 2:05pm |
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