Ramantanis Dimitris Posted September 4, 2016 Report Share Posted September 4, 2016 Is there any known solution to drive high voltage pulse TOYOTA tachometer? Quote Link to comment Share on other sites More sharing options...
Adamw Posted September 5, 2016 Report Share Posted September 5, 2016 First try a relay coil like this: http://www.haltech.com/wp-content/uploads/2013/07/Relay-Wiring-for-Tacho-Output1.pdf This will work for most hi level tachos. If you have no luck with that then there are devices such as MSD 8920 that will do it. Quote Link to comment Share on other sites More sharing options...
Ramantanis Dimitris Posted September 5, 2016 Author Report Share Posted September 5, 2016 There is no luck with this. I have tried...., any other options? Quote Link to comment Share on other sites More sharing options...
Ramantanis Dimitris Posted September 5, 2016 Author Report Share Posted September 5, 2016 I have also tried msd 8910, with no luck again, is 8920different? Quote Link to comment Share on other sites More sharing options...
Ramantanis Dimitris Posted September 5, 2016 Author Report Share Posted September 5, 2016 Ok I have made this work with the haltech diagram but with 0.33 kohm resistor. Is it a problem for the ecu safe?Shall I add a diode to protect the ecu output from over back current? Quote Link to comment Share on other sites More sharing options...
Scott Posted September 6, 2016 Report Share Posted September 6, 2016 No problem from the ECU side to use the 0.33 KOhm resistor. Does the relay already have a resistor or diode? Scott. Quote Link to comment Share on other sites More sharing options...
Ramantanis Dimitris Posted September 6, 2016 Author Report Share Posted September 6, 2016 No there no resistor in the relay. I simply done the schem above but with 0.33 kohm resistor. Is it safe for the ecu?Shall I use a diode at the ecu output signal? Quote Link to comment Share on other sites More sharing options...
Ramantanis Dimitris Posted September 6, 2016 Author Report Share Posted September 6, 2016 Another question is: The oem ac computer receives the same signal as tacho in order to see that engine runs and activate the compressor clutch. With this modification the ac ecu does not activate the clutch. Is there any possibily the current isnt enough strong to trigger the ac computer? fingers crossed... Quote Link to comment Share on other sites More sharing options...
bsh Posted September 6, 2016 Report Share Posted September 6, 2016 MSD 8920 normally works fine. Quote Link to comment Share on other sites More sharing options...
Scott Posted September 7, 2016 Report Share Posted September 7, 2016 No there no resistor in the relay. I simply done the schem above but with 0.33 kohm resistor. Is it safe for the ecu?Shall I use a diode at the ecu output signal?The ECU will be ok with no resistor or diode.Another question is: The oem ac computer receives the same signal as tacho in order to see that engine runs and activate the compressor clutch. With this modification the ac ecu does not activate the clutch. Is there any possibily the current isnt enough strong to trigger the ac computer? fingers crossed...This is possibly what is happening. The relay may be pulling down the amplitude of the tacho output. You would want to examine the signal with an oscilloscope to know for sure.Scott Quote Link to comment Share on other sites More sharing options...
Ramantanis Dimitris Posted September 7, 2016 Author Report Share Posted September 7, 2016 Another simplethings that works 100% is to use the oem's coil primary terminals. The connection is simple. + coil terminal connected to an IG+, - coil terminal connected to tachometer cable (as it was when OEM ecu was used) and tacho output from ecu connected to the coils edge - with a 0.33 kohm resistor. Same like the image that AdamW posted but in case of the relay coil we use the oem's coil primary terminals. Work 100% and also triggers the A/C OEM computer. Quote Link to comment Share on other sites More sharing options...
Adamw Posted September 7, 2016 Report Share Posted September 7, 2016 (edited) Another simplethings that works 100% is to use the oem's coil primary terminals. The connection is simple. + coil terminal connected to an IG+, - coil terminal connected to tachometer cable (as it was when OEM ecu was used) and tacho output from ecu connected to the coils edge - with a 0.33 kohm resistor.Edited my original post here since I had misread the resistor as 0.33ohm, not 0.33kohm which will limit current. Still not sure I like this idea... Edited September 7, 2016 by Adamw incorrect comments made Quote Link to comment Share on other sites More sharing options...
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