donedirty2010 Posted January 4, 2015 Report Share Posted January 4, 2015 Hello i am trying to figure out which is the power wire for the engine coolant temp sensor on an 87 nissan hardbody pickup..theres a black wire and a green wire can anyone tell me which is power and which is ground and do both of them need to be hooked up in order for the sensor to be operable ...any help would be appreciated..im running an aftermarket thermostat adapter because i am running dual weber DCOE carbs..and i really need my heater to work and i need this sensor to work in order to open the thermostat.. 1 Quote Link to comment
datzenmike Posted January 5, 2015 Report Share Posted January 5, 2015 Right that would be the Z24i engine. Well like all earlier Datsuns the temperature gauge is powered from a small voltage regulator supplying about 8 volts. (the fuel gauge is on the same volt regulator)This 8 volt signal can be maintained even though the battery voltage can fluctuate from 12 to 14+ volts. This keeps the gauges from fluctuating as well. Power flows first through the gauge, then to and is grounded by, the water temp sender unit below the thermostat to complete the circuit. The wire on the temp sender is Yellow/Red stripe according to my 86.5 D21 FSM.. So you have an electric operated thermostat???? I would get two thermostat covers from an L or Z series and sandwich a thermostat between them. Drill a small 3/32" or 1/8" hole in the thermostat as by-pass. Mount in line on the top rad hose as close to the head or intake as you can. How simple is that? Simply two tops bolted together with the thermostat inside. The small by-pass hole allows the stagnant cold water trapped behind the thermostat to be slowly displaced by the warmer hotter water from the head so the thermostat can sample it and react when hot enough. Too small a hole will cause the temp to spike and drop repeatedly until it stabilizes. Too large a hole and the warm up will be slow. 2 Quote Link to comment
donedirty2010 Posted January 5, 2015 Author Report Share Posted January 5, 2015 Its not electric...,however i am trying to use the stock wiring on the d21 to get this thermostat operational..there are 2 wires in my d21 a green and a black..i have the green hooked up to the adapter that came with my intake for the DCOE carbs from weber..and i just left the black wire unhooked..im not sure if i should ground it or not.. theres only 1 male on the adapter where the thermostat sits in ..so i was assuming it be for power so i spliced into the green wire and put a female on there and hooked them up...but when i warm up the truck the needle does not move on the temp guage and i am not gettin any hot air when i turn the heater on.. Quote Link to comment
datzenmike Posted January 6, 2015 Report Share Posted January 6, 2015 Its not electric...,however i am trying to use the stock wiring on the d21 to get this thermostat operational..there are 2 wires in my d21 a green and a black..i have the green hooked up to the adapter that came with my intake for the DCOE carbs from weber..and i just left the black wire unhooked..im not sure if i should ground it or not.. theres only 1 male on the adapter where the thermostat sits in ..so i was assuming it be for power so i spliced into the green wire and put a female on there and hooked them up...but when i warm up the truck the needle does not move on the temp guage and i am not gettin any hot air when i turn the heater on.. Not getting this. The thermostat is not electrical. The wiring has nothing to do with the thermostat. The thermostst works without it. If you have wiring to the thermosast housing then it's either for... 1/ The temperature gauge in the dash. 2/ The temperature sensor for the TBI throttle body injection. The ECU needs to know how warmed up or cold the engine is to set the correct mixture. I'll have another look when I get home tonight but if running carbs you won't need the TBI sensor but you will need the temperature sender for the gauge. Quote Link to comment
donedirty2010 Posted January 6, 2015 Author Report Share Posted January 6, 2015 Exactly...so i dnt think my thermostat is opening up then bcuz im not gettin much hot air with the heater on blast..and as far as the temperature sender.. i need that most importantly so that i can monitor whether or not i might be overheating.. so that means 1 of those 2 wires should give me a temp reading on the dash correct?! Quote Link to comment
datzenmike Posted January 7, 2015 Report Share Posted January 7, 2015 Right that would be the Z24i engine. Well like all earlier Datsuns the temperature gauge is powered from a small voltage regulator supplying about 8 volts. (the fuel gauge is on the same volt regulator)This 8 volt signal can be maintained even though the battery voltage can fluctuate from 12 to 14+ volts. This keeps the gauges from fluctuating as well. Power flows first through the gauge, then to and is grounded by, the water temp sender unit below the thermostat to complete the circuit. The wire on the temp sender is Yellow/Red stripe according to my 86.5 D21 FSM.. So you have an electric operated thermostat???? I would get two thermostat covers from an L or Z series and sandwich a thermostat between them. Drill a small 3/32" or 1/8" hole in the thermostat as by-pass. Mount in line on the top rad hose as close to the head or intake as you can. How simple is that? Simply two tops bolted together with the thermostat inside. The small by-pass hole allows the stagnant cold water trapped behind the thermostat to be slowly displaced by the warmer hotter water from the head so the thermostat can sample it and react when hot enough. Too small a hole will cause the temp to spike and drop repeatedly until it stabilizes. Too large a hole and the warm up will be slow. Already answered. The temperature sensor for the fuel injection (my mistake) is actually mounted in the head for a faster more accurate/realistic reading of the engine temperature. On the Z series this is on the exhaust side near the #2 plug. You should have a Yellow/Red stripe wire somewhere near the front of the intake or under it and to the rear of the alternator area. This is the water temperature gauge sender wire. Quote Link to comment
donedirty2010 Posted January 7, 2015 Author Report Share Posted January 7, 2015 Hmmmmmm.weird..bcuz i am running doug thorley headers and i dnt see any sensor located on the exhaust side in that area by the #2 plug..and the only wires located by the intake behind the alternator is the green wire and the black wire..so are u saying that theres 2 sensors that need to be working in order for my dash temp guage to work?! Which would be that sensor by the #2 plug on exhaust side and the water temp wire?! Or do i just need the water temp guage wire to be hooked up to get a reading on the dash..could that black wire be a ground..?! Quote Link to comment
datzenmike Posted January 7, 2015 Report Share Posted January 7, 2015 This is from an earlier Z series engine. Cylinder head sensor is just below the #1 plug and has two wires. Hmmmmmm.weird..bcuz i am running doug thorley headers and i dnt see any sensor located on the exhaust side in that area by the #2 plug..and the only wires located by the intake behind the alternator is the green wire and the black wire..so are u saying that theres 2 sensors that need to be working in order for my dash temp guage to work?! Which would be that sensor by the #2 plug on exhaust side and the water temp wire?! Or do i just need the water temp guage wire to be hooked up to get a reading on the dash..could that black wire be a ground..?! No I said there can be two senders, one for the gauge and one for the EFI. If you have wiring to the thermosast housing then it's either for... 1/ The temperature gauge in the dash. 2/ The temperature sensor for the TBI throttle body injection. The ECU needs to know how warmed up or cold the engine is to set the correct mixture. I have no idea what the green and black wires are. The D21 Hardbody has a Yellow/Red stripe wire for the temperature gauge. Maybe post a picture of the area and the green and black wire. We have simply overlooked something simple. Quote Link to comment
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