Yesterday I pulled out the water temp switch with the intent of replacing the 2 wires on it. The ground wire broke off right as it goes into the fitting (not wire to solder). Since its basically just a ground, if I fabed a washer with a ground wire and put it on the fitting as it goes into the thermo housing would this work? I'm not sure if the ground has to be intergral to the switch or if an external ground would work. Or should I just leave it non functional since it basically only affects cold starts. I have removed the EGR system from the intake by replacing the intake with a non EGR type.

Are you talking about the coolant temperature sensor (2-conductor Bosch style connector, smaller doodad, sends a temp reading to the ECU)?

Perhaps the thermotime switch (2-conductor Bosch style connector, larger doodad right next to the smaller one, turns the cold start injector on and off)?

I assume you're not talking about the temp sender with the single wire that runs to the temp gauge.

I'm guessing you're talking about the thermotime switch. If so, you're right that it will only help you with COLD starts (I think below 50F). The ground on the switch is the body itself. One wire on the connector operates an electric heating element, and the other wire switches the cold start valve. The connector is wired in parallel to the cold start valve connector. You wouldn't want to ground either wire. Grounding the heater wire would do nothing. Grounding the other wire would have your cold start valve constantly spraying.

BTW, you should download a free copy of Nissan's factory service manual:

www.xenons30.com

It has all the wiring diagrams you'll need. All mysteries of the Z universe will be revealed within!

Edited July 12, 201113 yr by FastWoman

Can't tell which of your cars you're talking about. But...

Federal models 1976, and I believe 75 and 77, have another temperature switch that "tells" the ignition module to use the other pickup coil in the distributor when the engine is cold. The extra pickup is set with an extra 6 degrees of timing advance. The ignition modules have a separate circuit just for the extra pickup coil. It went away in 1978.

Any ground from that wire should work as long as the switch closes when cold. It actually affects cold running, not just the start. Disconnected is like having a warm engine. If you leave it disconnected your idle will be a little low in the time between when the AAR closes after you start a cold engine and the engine gets fully warmed up.

It's been proposed (can't remember who it was) that you could put your own hand-operated switch in the circuit to give a manual 6 degree timing control.

FastWomen, no its not the thermotine or coolant sensor, its the water temp switch with no connector just two wires, from what I've read and Zed confirmed it has to do with the pickup coil(s).

Zed my car is a 75 and the problem is that I have literally no wire at all from the switch to run the ground which is why I was thinking that if I ran the ground from the body of the switch it might be OK otherwise its another $75 part.

You can take an ohm-meter and see if the wire is a redundant ground (like some relays have extra grounds). Check continuity from the body of the switch to the wire stub.

If the stub is not connected to the body then your fix won't work.

Maybe you could lay a drop of solder from the ire stub to the body or stake a tiny screw in to the remaining copper wire of the stub to make contact.

I had the same problem but had enough wire left to fix it. Eventually I stopped using the extra pickup coil though, that's how I know about the momentary low idle. The whole concept is kind of an engineering band-aid to keep the idle up while the engine gets warm. Kind of strange really.

Thanx Zed, I may try the small screw approach, I've got 2 of these with wires broken on both, so I tried to "engineer" a fix on one of them, I drilled out all the hard plastic on both sides, put screw with wire attached on the ground side and actually screwed it thru the bottem of the brass, the oter side has a small brass contact in the bottom with the wire attached to another small brass contact, so I soldered a new wire to the contact and put it into the hole to contact the the piece in the bottom and filled it with super glue. Who knows, it may work, but I doubt it.