1976 water temperature switch

[Captain Obvious]

The temp. switch is used only in 260Z with the automatic trans.

That is not correct. All the 260's use the temp switch regardless of the transmission type.

[Zed Head]

mousemedic might be going off of what is said in the 1974 FSM. Kudos to him for checking the factory source. It says that the automatic only used the water temp. switch to switch pickups in the distributor. Of course, 1974 is the year of change so it wouldn't be a surprise if the manuals had the switch also, like the 280Zs do (auto and manual), or they added it to the manuals when they went to the big bumpers.

To correct one thing in mm's post though, the timing is advanced when cold, then goes back to retarded when warm. My guess is it's another idle speed increaser, like the AAR. It's described n Engine Fuel, not Emissions. It seems like a lot of technology for an unexplained effect.

[Captain Obvious]

mousemedic might be going off of what is said in the 1974 FSM. Kudos to him for checking the factory source. It says that the automatic only used the water temp. switch to switch pickups in the distributor.

I don't know where he got his info from, but the way it's stated it's not correct.

All 74's used the water temp switch, not just the auto transmission versions.

On the manual's it was used to control the EGR function.

On the auto's it was used to control ignition timing, and the EGR function.

Maybe it's a language issue in the way it's being described? Switch a few words around and look what happens...

Incorrect - "The automatic only used the temp switch to switch pickups in the distributor." (the auto used it for more than just this)

Correct - "Only the automatic used the temp switch to control ignition timing." (OK since the manual trans cars didn't change ignition timing based on temperature).

"The temp. switch is used only in 260Z with the automatic trans." is incorrect on multiple levels since not only did all 74's use it, but on the automatic trans versions it was used for more than just ignition timing.

All good?

[Zed Head]

Just trying to help people get on the same page. In this case, page EE-27 of the 1974 FSM.

[Captain Obvious]

Just trying to help people get on the same page. In this case, page EE-27 of the 1974 FSM.

I've got no problem with that page except that it isn't the whole story. There's more to it than that.

Take a look at EC-16 and you'll see that the same switch and the same relay also controls the EGR function.

And that EGR control happens on every 260 regardless of what transmission it has.

Still not sure? Study the wiring diagram. It's there too.

[Zed Head]

I think that you're mistaking my quest for clarity and knowledge with a challenge to what you're saying. It's not. It's exactly what I wrote and the picture I posted.

mousemedic said "only", I showed why he might have said that. Now, you have shown, with your references, that there's more to the story.

This is the internet. The best way to get someone to believe the point you're making is with examples and references. Without those, how do you know if anyone really knows what they're talking about? And how do you explain it to someone else? "A guy from the internet said it was so". Thanks for the link to the EC section. Now we're learning.

[Captain Obvious]

I got no beef here. I just thought the whole thing was a little weird... Out of the blue, mousemedic resurrects a year and a half old thread and posts incorrect information about 260's when the original thread wasn't even about 260's in the first place. ???

I wasn't going to add anything more after my original post unless mousemedic came back and asked a question. I was expecting the whole thing to go back to sleep. I just didn't want it to go back to sleep on an incorrect note. I suspect that detailed discussion about the 74 temp switch in a "1976 water temperature switch" thread is likely to get passed by in the future. Probably best suited to a different thread with a more appropriate title.

I think that you're mistaking my quest for clarity and knowledge with a challenge to what you're saying.

Sorry. Yes, I did. It's because you asked no questions questing. It was all statements stating.

But if you're questing, I'm no expert, but I'm happy to do what I can to provide clarity and knowledge:

The 74 manual is admittedly obtuse when it comes to the temp switch. I've found the switch is described in multiple sections "functionally" instead of all in one place showing all the things the switch does. The only single source that I've found that shows everything in the same spot is the wiring diagram itself.

The 74 switch is open circuit when cool (below 77 degrees F) and closes when warm (above 88-106 degrees F). It has two connections, one to ground, and the other to the "EGR Relay". When the switch warms up, it energizes the coil of that relay. Note that different years switches operate differently.

On the wiring diagram, the water temp switch and the EGR Relay that it controls are both in the lower left corner. Note that there's a grounding mistake on the black wire from the temp switch (missing dot) on the diagram - Nothing connected to the temp switch would even work at all if the car were actually wired as it's drawn. The driver's side turn signal and marker lamp wouldn't work either.

The EGR Relay has two sets of contacts. The N/C contacts start closed (when the engine is cool) and go open when the engine warms up which enables the EGR system. The N/O contacts start open (when the engine is cool) and go closed when the engine warms up which (on the automatic transmission cars only) switches the ignition timing from advanced to retarded. The manual transmission cars have all the same wiring to the ignition module, but use a different ignition module that ignores the timing change signal.

I do not believe there are any other connections on the wiring diagram to anything involved with the temp switch and/or the relay that it controls. In other words, I believe the ignition timing and EGR functions are the only two things that the temp switch can possibly affect.

All 74's used the water temp switch, not just the auto transmission versions.

On the manual's it was used to control the EGR function.

On the auto's it was used to control ignition timing, and the EGR function.

If you were to use a manual trans ignition module on your auto car, your timing would be fixed to the advanced pickup.

If you have a manual trans car and have removed the EGR valve, then the water temp switch and the EGR relay are both doing absolutely nothing.

As before, I'm no expert, but I'm pretty comfortable with the 74 and the temp switch. I've been through the manual, I've studied the wiring diagram, I've tested the switch, I've tested the relay, I've redrawn the whole circuit in a form that makes more sense to me... And even after all that, it's still certainly conceivable that I've missed something and I'd be happy to hear about it.

[sblake01]

I got no beef here. I just thought the whole thing was a little weird... Out of the blue, mousemedic resurrects a year and a half old thread and posts incorrect information about 260's when the original thread wasn't even about 260's in the first place. ???

That pales in comparison to his opening up a 9 year old thread to imform three of our Australian members of something they werent actually discussing. The most recent visit from any of those three guys was in September 2010.........

http://www.classiczcars.com/forums/showthread.php?t=8328&p=401954&highlight=#post401954

Edited July 6, 2012 by sblake01

[Captain Obvious]

Haha! Exactly!! :laugh: I saw that too when it happened and almost said something about it.

"Holy Zombie!!! Ummmmm... You know this thread is like ten years old, don't you?"

Instead, like you, I just hoped it go away (again).

Same thing is happening on other forums as well...

I was originally thinking padding his thread count, but that doesn't seem to be the case...

[Zed Head]

I need to learn how to use them emoticons.

A lot of good information here anyway, as a result. I didn't know that the 260Zs were using EGR, it didn't show up on the Federal 280Zs until 77 or 78. I guess the EFI let Nissan back up a few years. Plus, the whole argument about not needing the switch if you don't need the extra distributor pickup becomes less relevant since the switch is used for EGR.

No harm, no foul:beard:

[Captain Obvious]

No harm, no foul :beard:

Absolutely!

I'm about out of time at this instant, but when I get a chance I'll port that 74 info over to it's own thread. I've been involved in a few discussions on the topic before, but I've never seen all the info in the same place at the same time. It would probably be helpful to 260 folks to remedy that.

I know the 74 OK, and I'm working on digesting the 77. Everything else before and after? Not my department.

Haven't thought about it in a while... Thanks for the refresher!!