L28 sensors

[ennisdavis]

Can someone tell me what each of these sensors are and if they can be tested out of the car. I dont want to buy new if they are functional.

[S30Driver]

The one at 11 o'clock is the all important coolant temp sensor that tells the ecu how much fuel for the injectors.   The big one at 2 o'clock is the thermotime switch which tells the cold start valve to add fuel and richen the mixture when ambient temps are low at startup.  The single pin one at 6 o'clock is the temp sensor for the gauge in the cabin.   You can easily test all except the themotime with a vom reading the resistance at a certain temp and referencing the factory shop manual guide. 

[dutchzcarguy]

4 hours ago, S30Driver said:

The big one at 2 o'clock is the thermotime switch which tells the cold start valve to add fuel and richen the mixture when ambient temps are low at startup. 

 

5 hours ago, S30Driver said:

You can easily test all except the themotime

Test this one in a pot of water on your stove, start with cold water and slowly make it hot.. at one point you should see the sensor switch.

[ennisdavis]

You mention 3 sensors, there are 4 in the picture

[Zed Head]

The crusty one on the side is probably a switch.  Nissan used a variety of combinations of switches over the years.  Without the year of vehicle and engine a person can only guess.

[zspert]

That switch was  was used in 75 and 76 only. 

[S30Driver]

Zspert .. are those cromodora wheels?    Looks great on that car.

[EuroDat]

I believe the side sensor is for the factory airco on the 280Z.

I can't find it in the wiring diagram.

 

Edited May 14, 2022 by EuroDat

[zspert]

S30driver - they're 14 inch Campagnolo wheels. I purchased them new in the early 90s from the late Al Costintino (sp) the US importer.  Manufactured to a high standard and complete with Campy lug nuts!

That sensor, the one on the side by itself, didn't appear in 77 or 78 - with or without factory a/c.

[EuroDat]

14 minutes ago, zspert said:

That sensor, the one on the side by itself, didn't appear in 77 or 78 - with or without factory a/c.

I agree. I have seen it mentioned as a thermo switch for the airco in other threads, but I can't find anything about it in the AC wiring diagram. My 280Z has factory air and doesn't have the switch.

Maybe @ennisdavis can tell us which L28 he is refering to. Could be something ZX....

[Zed Head]

I browsed through a bunch of carpartsmanual pages and only found one drawing of the thermostat housing, in EFI Control.  It does show a side port but I can't find a switch defined for the hole anywhere on the other pages.  The carparts site is setup in a way that you have to know something's purpose before you know where to find it on the site.

http://www.carpartsmanual.com/datsun/Z-1969-1978/engine-280z/e-f-i/control

[Dave WM]

1. water temp switch on my 75 Cali car was for the EGR system. It is disabled during warm up with an electrically controlled vacuum source. I have had a few of both the thermotime as well as the temp switch. Most of the used ones did not function. I presume corrosion was the factor. The temp switch in my case was a NC below 140f IIRC, I ended up making my own with an old housing and a new temp controlled reed style switch, epoxied into place. I think the main problem I had finding a new temp switch was most were NO at below 140f and would close once the engine would warm up. Not what the EGR wanted.

I think on others the temp switch had to do with switching the dual coil distributer pickups for different advance one full temp was achieved.

Edited May 15, 2022 by Dave WM