914 cutting out I found the problem

[Dave Schiel]

How do you replace a Thermotime Switch/ head temp switch on a 74 914 1.8

[Dave at Pelican Parts]

Those are two different sensors. The thermo-time switch (TTS) is up on top of the engine, on a bracket from the mounting legs for the intake air plenum (AKA the manifold).

The CHT sensor (Temp Sensor II) is in the right-side cylinder head near spark plug #3, and seems to have been the problem in your previous post. This sensor is threaded directly into the aluminum head, and it likes to bring threads out with it when you remove it. Which is a real pain to fix without removing the head from the engine, which you almost have to drop the engine to do.

A deep-well 13mm socket can be used on the sender. You can coil up the wire inside the socket. I have also seen sockets with a slice cut in them for the wire to go through, or an extension with one corner knocked off the end (with a grinder) that plugs into the socket, to leave a gap for the wire.

I have heard that you should get the engine up to operating temp before removing the sensor because the aluminum hole will expand more than the steel sensor. I have also heard that you should do the job when the engine is cold because the aluminum threads will be weak if they're hot. I'm frankly not sure what works. I stripped one on my car and have been pretty scared of them since. (It led to a lot of "while you're in there" stuff.) I would suggest a good penetrating oil at a minimum, something like PB Blaster or Kano's Aero Kroyl. (WD-40 is not a penetrating oil.)

Or see if a shop will take on the job.

--DD

[TheCabinetmaker]

dito that , use lots of penatrating oil the day or two before attempting removal. the new head temp switch should be liberally coated with anti-sieze,and besure to use a new crushable washer under it , this helps thermal contact.

the time switch if it is anything like on a D-jet is easier to replace, unscrew from bracket for replacement

[TheCabinetmaker]

PS Often these head temp sendors can be repaired, Often it is simply the wire pigtail that has broken internally causing an open, or the insulation has failed near the crimp, causing a short. with some careful soldering and sleaving , this can be repaired, maybe repair it and save as a spare for roadside repairs. dont toss the old one unless your sure it is not a wire open/short issue. These are often the cuase for an intermittant head temp sendor failure