Thermo Time Switch Watt Rating?

[Phlown]

Looking to replace the VDO TTS for my 1980 SC. Found a VDO TTS with same part number, but mine has 40W engraved on it, the potential replacement has 3W engraved. Confused, wondering if part will work for me. Thanks for any input!

[steely]

Welcome to the site!

Not familiar with the 3W, but my uneducated guess is that they included a power rating for the switch contacts, and it seems low if it is used in conjunction with something like a cold start valve that might need 2 or 3 amps (24-36W), but I could be way off.

Can you see/give us the part number?

[Phlown]

Thanks steely for the welcome. Have been a long time lurker!

Below are couple pics of mine. The part number on replacement is same as mine, but where mine shows 40W it shows 3W. Just seems strange! Thanks for getting back to me.

[Porboynz]

Use a relay as well

[steely]

Originally Posted by Phlown

Thanks steely for the welcome. Have been a long time lurker!

Below are couple pics of mine. The part number on replacement is same as mine, but where mine shows 40W it shows 3W. Just seems strange! Thanks for getting back to me.

You are welcome sir - but I wish I had more info for you.
What model year do you have and is the TTS for the CSV?
Can you post a pic of your car - and the new candidate TTS?

cheers

[Phlown]

I have a 1980 911 SC Targa. Couple pics below (clearly I need to take some better pictures!) Yes, the TTS is for the CSV. Also pic of candidate TTS. Thanks again steely.

[steely]

Many thanks for the explanation L.J.
That makes so much sense.
Would you know offhand how this affects the time rating, for example does it take longer to warm up with fewer watts, or is it fast acting (to open the switch)?
I guess it should be obvious to me but I don't see it.
Thanks again

[steely]

Originally Posted by Phlown

I have a 1980 911 SC Targa. Couple pics below (clearly I need to take some better pictures!) Yes, the TTS is for the CSV. Also pic of candidate TTS. Thanks again steely.

Beautiful car Phlown!
PS - I can't make out the PN on the candidate TTS, but it may not matter.

[ossiblue]

Originally Posted by steely

Many thanks for the explanation L.J.
That makes so much sense.
Would you know offhand how this affects the time rating, for example does it take longer to warm up with fewer watts, or is it fast acting (to open the switch)?
I guess it should be obvious to me but I don't see it.
Thanks again

I did a little more research and have since deleted my post as you typed. (Your post is going to look odd now that my comments have been deleted ) Researching the part number only returns TTS that have 40W ratings. As I stated, I'm no expert so this. It's going to depend on the manufacturer of the TTS you found. It made sense to me that 3W for the heating element is reasonable and I found mention of the 3W heating element in a past post on the forum, but if the rating is for the contacts, it would not work. Bosch parts all seem to have 40W ratings.

Now, all that being said, amperage is typically used to express switch loads, not wattage. Wattage is typically found on heating devices, however. Again, I'm not schooled on TTS, but I think it's logical to think the 40W and 3W stamps are comparisons of the heating element and not the switch load. Unless I'm missing something (and that's quite possible), a heating element marked with the higher wattage will be a quicker heating element.

Where did you purchase the TTS and what is the manufacturer? If it's an off brand, perhaps they labeled the heater wattage rather than the contact wattage.

[Phlown]

Thanks so much Dan and L.J. for weighing in here. The replacement I'm looking at (haven't bought yet pending this issue!) is a VDO TTS, just like the one in my car, and the part number is identical. In fact on the six faces with engraving, four are identical, only differences being the one with the watt rating, one with what I think may be some kind of VDO reference system.

Knowing that the part number is correct for my car, and that the place I'm dealing with has quite a few of these 3W, advertise them for my car year, and told me they have sold a few with no returns, I'm tempted to give one a whirl. (Obviously I'm one of those very detailed guys who tends to analyze things down to a gnat's ass!)

What do you think?

[ossiblue]

Originally Posted by Phlown

Thanks so much Dan and L.J. for weighing in here. The replacement I'm looking at (haven't bought yet pending this issue!) is a VDO TTS, just like the one in my car, and the part number is identical. In fact on the six faces with engraving, four are identical, only differences being the one with the watt rating, one with what I think may be some kind of VDO reference system.

Knowing that the part number is correct for my car, and that the place I'm dealing with has quite a few of these 3W, advertise them for my car year, and told me they have sold a few with no returns, I'm tempted to give one a whirl. (Obviously I'm one of those very detailed guys who tends to analyze things down to a gnat's ass!)

What do you think?

Personally, I'd be inclined to go with the replacement. A TTS doesn't usually cause noticeable problems because it only operates for a short time--during cold start cranking--and even if the heating element is completely shot, the contacts will open from engine heat. You would notice a faulty element if the CSV still worked after more than ~8 secs. of cranking or it worked when the engine was slightly warm. It's the heating element that puts the "Time" in Thermo Time Switch.

Still, it might put you at ease to call around to a Porsche shop and ask specifically about the different wattages. These TTS are used in cars other than 911's.

[steely]

Originally Posted by ossiblue

I did a little more research and have since deleted my post as you typed. (Your post is going to look odd now that my comments have been deleted ) Researching the part number only returns TTS that have 40W ratings. As I stated, I'm no expert so this. It's going to depend on the manufacturer of the TTS you found. It made sense to me that 3W for the heating element is reasonable and I found mention of the 3W heating element in a past post on the forum, but if the rating is for the contacts, it would not work. Bosch parts all seem to have 40W ratings.

Now, all that being said, amperage is typically used to express switch loads, not wattage. Wattage is typically found on heating devices, however. Again, I'm not schooled on TTS, but I think it's logical to think the 40W and 3W stamps are comparisons of the heating element and not the switch load. Unless I'm missing something (and that's quite possible), a heating element marked with the higher wattage will be a quicker heating element.

Where did you purchase the TTS and what is the manufacturer? If it's an off brand, perhaps they labeled the heater wattage rather than the contact wattage.

Aw, you could've left it - the cartoon/schematic was helpful.

[ossiblue]

Originally Posted by steely

Aw, you could've left it - the cartoon/schematic was helpful.

Just for you, steely

[Phlown]

Thanks L.J., at this point I'm inclined to try it. Btw, I like your illustration also, not even knowing its inspiration!

In reading through your last comments, thought I would provide short story version of how I got to replacing TTS. Out of nowhere, cold start problem (probably a statement most all 911 owners of this generation have uttered at least once!) With my Brentley and another troubleshooting guide, got after it. Had recently replaced the starter, so checked connections (yellow wire.) Tested fuel pressure, checked pertinent fuse, relay. Checked air flow sensor plate- fine. Just will not start. So went to TTS. Checked continuity, wire voltage with starter actuated - failed continuity test. Pulled it, bench tested cold and hot. Out of Bosch spec range (could not find VDO specs) in 5 of the 6 tests. Thus, the pursuit of a TTS.

Any comments on process, am I pursuing TTS at proper time sequence?

Thanks!

[boyt911sc]

Originally Posted by Phlown

Thanks L.J., at this point I'm inclined to try it. Btw, I like your illustration also, not even knowing its inspiration!

In reading through your last comments, thought I would provide short story version of how I got to replacing TTS. Out of nowhere, cold start problem (probably a statement most all 911 owners of this generation have uttered at least once!) With my Brentley and another troubleshooting guide, got after it. Had recently replaced the starter, so checked connections (yellow wire.) Tested fuel pressure, checked pertinent fuse, relay. Checked air flow sensor plate- fine. Just will not start. So went to TTS. Checked continuity, wire voltage with starter actuated - failed continuity test. Pulled it, bench tested cold and hot. Out of Bosch spec range (could not find VDO specs) in 5 of the 6 tests. Thus, the pursuit of a TTS.

Any comments on process, am I pursuing TTS at proper time sequence?

Thanks!

Phlown,

Continuity test between what 2 points in the TTS? Thanks.

Tony

[steely]

Originally Posted by ossiblue

Just for you, steely

[im]

[Phlown]

Hi Tony. Between G and W terminals with wiring harness removed from switch, starter activated. Thanks!

[boyt911sc]

Originally Posted by Phlown

Hi Tony. Between G and W terminals with wiring harness removed from switch, starter activated. Thanks!

Phlown,

At room temp. a good TTS has continuity between:
a). G & W.
b). G & ground (TTS body).
c). W & ground (TTS body).

A good TTS above 113°F:
a). No continuity.
b). No continuity.
c). No continuity.

The resistance of the heater is about 24~25 Ohms. The starter has nothing to do with TTS once you disconnected the wire harness to TTS.

Tony

[Phlown]

Hey Tony. Thanks again for your response. Not sure I worded all my comments correctly about TTS. But pertinent points currently about testing my TTS: did the Brentley outlined test of removing the wiring harness from TTS, connected test light across terminals, had someone actuate starter. No light. That led to pulling TTS, bench tested hot and cold, and results were outside Bosch specs. My TTS is a VDO made switch, could not find specs, read somewhere probably similar to Bosch (which I now believe to be a bad assumption.) Thus the search for a replacement, the 3W vs. 40W switch.

I went ahead and bought the 3W switch (with return privilege) which arrived couple days ago. Yesterday, before installing, decided to put ohm meter to it and found that it spec'd out almost exactly to the switch I was going to replace - enter bad feeling! Installed, tried to start car - same problem, cranks like a champ, won't start.

So, now questioning if TTS is the problem. I know there is current in yellow wire from starter to TTS (test light) but haven't measured voltage at TTS, so about to test that. Also considering testing CSV itself, wonderful thought considering I'm not in a situation where I can drop engine! Have taken a look at with a mirror, removing two mount screws, although a challenge, pretty certain I can get done. Test itself looks very tricky to do - blind element, tight space.

Definitely at rising frustration level. This car was running like a bullet! New starter, just dialing in lean/rich setting with idle mixture on AFS, tweaking idle bypass. Still hadn't quite hit sweet spot (throttle needed feathering at stop signs), arrived at a stop sign, engine died, and since then have only got it started once (short ride, same idle issues) many No Deal start attempts. And as listed in couple posts above, have done a fair amount of successful, pertinent testing.

NOTE: Just went out to car, removed wire harness at TTS, took voltage readings on Yellow wire and Blk/Rd wire with starter actuated - 10.2V on each. Is that a problem? (Battery fully charged, recently had load tested, no problems.)

Again, many thanks in advance for help, suggestions. Love learning from the many here so much smarter about this car than I am!

Phil

[Phlown]

Greetings. Can anyone respond to my NOTE above? Will paste it below - thanks much!

NOTE: Just went out to car, removed wire harness at TTS, took voltage readings on Yellow wire and Blk/Rd wire with starter actuated - 10.2V on each. Is that a problem? (Battery fully charged, recently had load tested, no problems