regggggggg Posted October 8, 2012 Share Posted October 8, 2012 Hello everyone! I just finished swapping an RB20DET motor into my '72 240Z and it is now running. The only problem is that I do not have a tach or temp gauge hooked up. The tach isn't a big issue right now, but i have no idea how hot my engine is running and i wanted to know if i would be able to hook up the stock coolant temp gauge on the z? I also have a wiring specialties harness that has outputs for those two signals but i don't know if they would work. If anyone has any ideas, please let me know. thanks! Quote Link to comment Share on other sites More sharing options...
OldAndyAndTheSea Posted October 8, 2012 Share Posted October 8, 2012 (edited) The temp gauge should be an easy fix as well. I cannot remember definitively what the color of the coolant temp sensor wire, but a part of me believes it is (yellow, possibly with a black line) Confirm anyone? But I'd reuse the stock coolant sensor (240z) in your thermostat housing routed to the yellow/black wire, which is hopefully still wired to your gauge. Edit: Just saw you have a different harness. I'm still assuming the stock sender will work with the stock gauge. Edited October 8, 2012 by OldAndyAndTheSea Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted October 9, 2012 Share Posted October 9, 2012 Temp sensor part number 25080-89903 NISSAN The tach is a bit more in depth. You will have to find a resistor and use a power pullup to amplify the tach signal enough to run the stock tach if you have a 3 wire tach. If you have a 4 wire tach I cannot help you as I am not an electrical engineer and I stumbled across the power pull up wiring by accident. My resistor is a 194 light bulb... If this sounds complicated search a bit then start asking questions. Both of these questions have been covered extensively on this board and its even in the sticky above this post by Chris Rummel. Ray Quote Link to comment Share on other sites More sharing options...
wrcbonk Posted October 9, 2012 Share Posted October 9, 2012 The temp sensor is easy like Ray said, but be smarter than me. Put a dab of rtv on the temp sensor threads or you will NOT get coolant weeping out when the system gets hot. The tach depends like ray said. I have a '71 so I was stuck with the super old school 4-wire tach. I tried a lot of different things to "amplify" the tach signal coming out of your rb wiring harness and no dice! I finally threw my hands up and ordered an auto meter tach. I have some pics of the pod swap if you need them. Its not rocket science, you just need to not be in a hurry and enjoy geeking out on stuff like retro fitting new signal indicator lights. Bill Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted October 10, 2012 Share Posted October 10, 2012 The 4 wire tach is an inductive pickup with the ignition wire from the key going through it on its way to the coil. I think the signal can be boosted like the 3 wire, but Im not sure. Possibly put the booster on the ground side? I never use that type of tach so Im only guessing, but I have had to repair stock 240Z 4 wire tachs when they dont work (like when someone wires their coil up wrong)so I know the circuit and basis of how it works. Quote Link to comment Share on other sites More sharing options...
mtnickel Posted December 18, 2014 Share Posted December 18, 2014 Temp sensor part number 25080-89903 NISSAN The tach is a bit more in depth. You will have to find a resistor and use a power pullup to amplify the tach signal enough to run the stock tach if you have a 3 wire tach. If you have a 4 wire tach I cannot help you as I am not an electrical engineer and I stumbled across the power pull up wiring by accident. My resistor is a 194 light bulb... If this sounds complicated search a bit then start asking questions. Both of these questions have been covered extensively on this board and its even in the sticky above this post by Chris Rummel. Ray Does anyone have the resistance values for the stock gauge and for this sensor? I got my rb25 running the other day and used what i believe is the sensor listed above (except from Beck Arnley). It was measuring about 1.5k cold and about 80 ohms at operating temperature. However, the gauge does not read 180-190 deg (like my tuning software and thermostat indicate). It was showing only just over the base 120 (perhaps 130ish). It's an early 260z. So curious if the earlier 240z gauges had a different resistance scale for the coolant gauge, or whether I got a dud sensor. If anyone running the nissan sensor listed could let me know the resistance at operating temperature, it would be appreciated. Quote Link to comment Share on other sites More sharing options...
mtnickel Posted December 18, 2014 Share Posted December 18, 2014 Nevermind. I looked up the part number and saw it is spec'd for the z32. Upon looking up the Z32 FSM, i found it should read: 70-90ohms @ 60*C (140*F) 21-24ohms @ 100*C (212*F). So it appears my sensor is probably incorrect. Slight chance I have foam/air in my cooling system that is causing it not to read full temp as well. Posted spec for those interested. Stock 260z gauge reads roughly 130-140* at the 80 ohms I measured, so the z32 sensor seems correct. Does anyone have the resistance values for the stock gauge and for this sensor? I got my rb25 running the other day and used what i believe is the sensor listed above (except from Beck Arnley). It was measuring about 1.5k cold and about 80 ohms at operating temperature. However, the gauge does not read 180-190 deg (like my tuning software and thermostat indicate). It was showing only just over the base 120 (perhaps 130ish). It's an early 260z. So curious if the earlier 240z gauges had a different resistance scale for the coolant gauge, or whether I got a dud sensor. If anyone running the nissan sensor listed could let me know the resistance at operating temperature, it would be appreciated. Quote Link to comment Share on other sites More sharing options...
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