TieFighter88 Posted June 23, 2012 Share Posted June 23, 2012 The temperature gauge in my dash just reads maximum when I turn the ignition on, and whilst I have the engine running... Retracing and repairing the wiring throughout the engine... I found after tracing the wiring harness has a pair of wires snipped and free without a connection, they are both green and were taped with the wires that run to the thermotime switch. Can somebody please identify the components of the thermostat housing in the photo I uploaded? Off the top of my head, 1: ? 2: ? 3: Water temp sensor 4: Thermotime Switch Quote Link to comment Share on other sites More sharing options...
TieFighter88 Posted June 23, 2012 Author Share Posted June 23, 2012 (edited) Been searching through my service manual and I cant locate a diagram ... L28 F54 Block N42 Head, discovered that the block is from a (1981-1983) 280zx, so will check out the 280zx service manual then... Yet the Head is from the 75-76 280z... will check out that manual also then... Edited June 23, 2012 by TieFighter88 Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 23, 2012 Share Posted June 23, 2012 The thermostat housings are interchangeable. Looks like probably the 78 housing in your picture. I think that the gauge uses resistance to ground, so measure resistance from the pin on the sensor to ground first to see if the sensor is good. If it is, work backward looking for a short. If it's shorted, you probably have a bad sensor. The description might be in Body Electrical under gauges. Or Engine Electrical. Should be in the 78 FSM. Quote Link to comment Share on other sites More sharing options...
stravi757 Posted June 23, 2012 Share Posted June 23, 2012 (edited) Looks like a 280zx thermo housing to me. My bet is that the water temp sender you have there is for a 280zx or vice versa, which would explain a bad reading. Edited June 23, 2012 by stravi757 Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 23, 2012 Share Posted June 23, 2012 Rock Auto and OReilly sell the same part for a 1976 280Z and a 1982 280ZX. I'm guessing the thermal transmitter, aka temperature sender, is the same for both. Page BE-42 in the 76 FSM describes operation. Measure resistance and you'll get an idea if its working. Zero and infinity are bad. Quote Link to comment Share on other sites More sharing options...
TieFighter88 Posted June 23, 2012 Author Share Posted June 23, 2012 Thermo Housing is that of a 280zx Quote Link to comment Share on other sites More sharing options...
stravi757 Posted June 23, 2012 Share Posted June 23, 2012 Rock Auto and OReilly sell the same part for a 1976 280Z and a 1982 280ZX. I'm guessing the thermal transmitter, aka temperature sender, is the same for both. Page BE-42 in the 76 FSM describes operation. Measure resistance and you'll get an idea if its working. Zero and infinity are bad. Im fairly sure they are different from each other. Quote Link to comment Share on other sites More sharing options...
TieFighter88 Posted June 23, 2012 Author Share Posted June 23, 2012 from "http://www.zcar.com/70-83_tech_discussion_forum/where_is_temp_sensor_81_280zx_644149.0.html" The following is for a 79, the location of the sensors may be different for an 81 but the description of what they do is correct Looking at the motor from the front, the thermostat housing has the following items: At 2:00 o'clock the "Water Temperature Sensing Switch". It controls the fan which blows air towards the injectors / intake manifold when the coolant temperature is above 110C. It has a single wire connected to it with a "male" bullet connector at the end of the wire. (it is usually green and about 2" long) At 4:00 o'clock the "Water Temperature Sensor". It is connected to the ECU and provides coolant temperature readings in the form of a change in resistance. As the coolant temperature increases the resistance decreases. This sensor works in conjunction with the "Air Temperature Sensor" in the AFM and is also connected to the ECU. These two sensors provide input to the ECU so that the ECU can change the fuel injector pulse width. At 8:00 o'clock the "Thermotime Switch". It is connected to the "Cold Start Valve". At 10:00 o'clock the "Thermal Transmitter". It is connected to the Temperature Gauge in the Dash. It has a single "male" bullet connector built into the end of the sensor. Wayne Monteath Masham, Quebec. Quote Link to comment Share on other sites More sharing options...
TieFighter88 Posted June 23, 2012 Author Share Posted June 23, 2012 Broke the lower thermostat housing whilst tightening at the thermal transmitter, didn't take much at all... After disconnecting all of the wiring from the thermostat housing, the temp gauge still gets a reading from something...still Maxed out... Quote Link to comment Share on other sites More sharing options...
TieFighter88 Posted June 23, 2012 Author Share Posted June 23, 2012 Still reads maximum when I ground the connector also... will follow the wiring through the dash... Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 23, 2012 Share Posted June 23, 2012 Im fairly sure they are different from each other. Another puzzle. I'm just working from the sources available. Definitely something for the OP to consider. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted June 23, 2012 Share Posted June 23, 2012 Broke the lower thermostat housing whilst tightening at the thermal transmitter, didn't take much at all... After disconnecting all of the wiring from the thermostat housing, the temp gauge still gets a reading from something...still Maxed out... Yeah I did that once. I had to buy a spare one off a member here. It cost me $50 and left me stranded for a few days in FL. The thermo housings are matched to the head not the block, so it depends on what head you have (N47 or P79/p90) It being maxed out means that it is grounding somewhere. When it is disconnected it should read 0 and when you put the wire to ground it jumps all the way to 270. For my connections, my top right is my electric cooling fan sensor ( threw that away and disconnected the wires), bottom right is my temp gauge sensor(they sell them at autozone for $15-$20 and when I changed mine my temp reading shot up consistently because my old sensor was corroded), the bottom left is a vacuum block that I assume assume is what was connected to the idle up/cold start system, and finally the top left is the thing with the green 2" wire sticking out (I noticed no difference of having it connected and having it not connected. I keep it connected just because I don't want a wire dangling around near my fan.) So basically my 4 o'clock and 10 o'clock are switched. My engine is from an 81, that I had rebuilt using a p90 head. Used my old Thermostat housing though (p79 housing). Quote Link to comment Share on other sites More sharing options...
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