A tale of two TTS’s

[Funracer]

Tested my original (I think) TTS last winter while the engine was out. It showed continuity across the W and G terminals but was stuck closed. Even heating it to 90C it still would not open. Did it again today with same results.



So I bought a a new one and put it in. Looks a bit different but its listed on Pelican Parts as the correct part for my car. Has the same 45C temp spec on it. Cannot remember if I tested it prior to install.



Now, 8 months later, troublshooting a hard cold start, I never considered this part would not work because it was brand new. Now I am not sure. Measuring across W and G I get nothing, no continuity or resistance when cold (32C) with it installed as in the picture. I even iced it down for an hour to try and force the thermal switch to close.
Nothing changed. No continuity.



Of course its an electrical part so no returns. Should I bother to look for voltage at the CSV or is this TTS dead too for sure? Darn things are pricey.

Thanks

[Funracer]

Anyone?

[JSV798]

Here is a link to how TTTs work; not from a 911 but similar.

https://www.sw-em.com/bosch_d-jetronic_injection.htm#Thermo-Time_Switch

Roy

[JSV798]

So I would expect continuity between G and W when cold. You could try connecting W and G with a jumper lead and see if the car starts from cold as long as you don't operate the starter for too long. If the car starts you have your answer.

Roy

[Funracer]

Originally Posted by JSV798

So I would expect continuity between G and W when cold. You could try connecting W and G with a jumper lead and see if the car starts from cold as long as you don't operate the starter for too long. If the car starts you have your answer.

Roy

Ha great idea! I was just waking up this morning and thought to do the same thing.

So the VDO TTS lasted 40 years and the aftermarket one lasted less than a year. Crazy.

Thanks

[JSV798]

Checked the TTs on my car (1978SC) this morning and when cold I have continuity. Took it for a short drive and then afterwards with a warm engine there was open circuit between W an G, so looks like your TTS is broken.

Roy

[boyt911sc]

Neil,

I have a TTS tester if you like them tested and evaluated. Will return them back to you via Priority Mail the day after I received the package. It would only take a minute to do the test. PM me if you are interested. Thanks.

Tony

[Funracer]

Thanks Tony. PM sent

[boyt911sc]

Neil,

Here are the test results:



The TTS on top is GOOD. While the other one at the bottom of the picture failed the test. This one is always open for a long long time. Did not bother to find the duration of on-time. Will send them back to you tomorrow. Thanks.

Tony