Thermotime Switch - How long do they last and what causes failure?

[kings1527]

Average lifespan, I mean. Thoughts?

[DMCMW Dave]

Average lifespan, I mean. Thoughts?

Most of them are 32 years old.

The ones that are replaced are often replaced in error due to misdiagnosis of other problems.

The main thing that causes replacement is breaking off the shell around the connectors, and if you then hook it up backwards it will burn out the switch.

Things wear out.

[David T]

Most of them are 32 years old.

The ones that are replaced are often replaced in error due to misdiagnosis of other problems.

The main thing that causes replacement is breaking off the shell around the connectors, and if you then hook it up backwards it will burn out the switch.

Things wear out.

All of the above but on many cars it has been INOP for a long time, no one knew how to make it work correctly or that it wasn't working! Some cars have some "creative" wiring mods in this circuit. None seem to work any better than the stock system hooked up and working correctly. As Dave points out, it is more than just a simple switch, there is a heater/timer element built into it and if it is hooked up incorrectly it can be damaged. Polarity to this is switch is VERY important! Not a high failure rate on this switch but it is on the expensive side and they are getting rare.

[kings1527]

Thanks for the input, guys. My cold start system is acting up and I don't know why. My TTS is about brand new so I think I'm looking at the horrible electrical connection as being the likely culprit. I think one of my pins on the car's wiring isn't capturing one of the pins on the TTS; I think it's being driven between the plastic housing and the metal connector instead of going inside the metal connector on the car's wiring. The plug swap causes it to fire right up but I'm going to do more diagnostics today and see if I can pinpoint it.

[DMCMW Dave]

Thanks for the input, guys. My cold start system is acting up and I don't know why. My TTS is about brand new so I think I'm looking at the horrible electrical connection as being the likely culprit. I think one of my pins on the car's wiring isn't capturing one of the pins on the TTS; I think it's being driven between the plastic housing and the metal connector instead of going inside the metal connector on the car's wiring. The plug swap causes it to fire right up but I'm going to do more diagnostics today and see if I can pinpoint it.

On some cars the circuit is powered by the blue/yellow wire FROM the starter. If that connection (about 4 inches from the starter) is poor, the car will crank but you will have a weak/no voltage to the TTS and to the ballast resistor bypass, both of which will contribute to making the car hard to start.

On other cars it is powered by the ignition white/red trigger line. This is what is shown on the common schematic, but there are differences in the cars.

[kings1527]

Thanks for the info, Dave. I'll do some rooting around and try to figure this out.

[kings1527]

So I jingled the wires around a couple days ago and got everything connected securely, I had hoped. But I didn't have time to test things until today. I went the easy route first, and with an engine that hadn't been started in about three days I disconnected the cold start valve and stuck it in a jar. I disconnected the wires at the ballast resistor and cranked the engine and happily there was about 5cc or so of fuel in the jar.

I connected everything back up and it fired up like it always did for a cold engine start, within about 2 seconds of cranking. So, I've gotta leave it to that horrible electrical connection and I've had that issue before when I put the manifold back on and re-connected everything. But thanks for the info, Dave. I'm glad I didn't have to hunt down a power issue or spend $160 for a new TTS.

[DMCMW Dave]

So I jingled the wires around a couple days ago and got everything connected securely, I had hoped. But I didn't have time to test things until today. I went the easy route first, and with an engine that hadn't been started in about three days I disconnected the cold start valve and stuck it in a jar. I disconnected the wires at the ballast resistor and cranked the engine and happily there was about 5cc or so of fuel in the jar.

I connected everything back up and it fired up like it always did for a cold engine start, within about 2 seconds of cranking. So, I've gotta leave it to that horrible electrical connection and I've had that issue before when I put the manifold back on and re-connected everything. But thanks for the info, Dave. I'm glad I didn't have to hunt down a power issue or spend $160 for a new TTS.

You would not believe how many people Julee talks out of buying a thermotime switch.

[kings1527]

You would not believe how many people Julee talks out of buying a thermotime switch.

We really appreciate the honest business, Dave. It can be so hard to find nowadays.

[AirmanPika]

Mine was actually split open (on the inside, not the connector side). The symptom was it was the fans always ran (which I guess is good from a failure standpoint). After replacement its all happy again.

[DMCMW Dave]

Mine was actually split open (on the inside, not the connector side). The symptom was it was the fans always ran (which I guess is good from a failure standpoint). After replacement its all happy again.

Wrong switch.

[AirmanPika]

Wrong switch.

Whoops yes brainfart on my part. Disregard me.