TTS testing question
 

I performed a bench test of my TTS and was wondering if Tony or others in the know could tell me if the results indicate a good switch.
1982 SC, 45 deg.C VDO TTS. Cold, I get 25 ohms from G to ground and 0.5 ohms from W to ground. I hooked up a test rig per Tony's instructions but I substituted a voltmeter instead of a test light (all I had with me). I could verify the switch was closed when cold by getting 12 V from the battery through W to ground. I then hooked G to power and lost voltage after 2 seconds.
Does this indicate a good TTS? I'm just a little surprised that it only took 2 seconds to heat the element up enough to open the switch. Is this normal.

Doing the test highlighted a couple of other points to me I didn't realize before. Firstly, if my valve is operating correctly then the CSV only fires for about 2 seconds, just enough to help start the car and nothing more.
Also, and more importantly, once the heating element has been heated in those first few seconds, it takes quite a while to cool down and ground the CSV again. So, if your car doesn't fire up on the first crank, then it is likely that on subsequent cranks right after that you are not getting the benefit of the CSV.

tony has done more testing on this than me but that sounds right.
2 seconds of extra fuel is quite a bit. you don't want to flood it and you don't need it on a warm engine.

Now I am just talking based on memory.

CSV fires the entire time starter is cranking if temp is below the warm temp threshold.

Although two seconds should be plenty with the aggressive fog of fuel it delivers, it should not cut off at two seconds.

TTS test duration........
 

I was getting a duration between 6~8 sec. at room temp. for the TTS to switch off using a test light as indicator.

Tony

the initial TTS temp should change that time a little, no?

Thermal switching........
 

Ty,

A good TTS does the switching @ 113°F (+/-). ON below 113°F and OFF above 113°F. The ambient temperature has a direct effect on the duration of the TTS operation. If your car is located in Montreal or in Myrtle Beach today, the time to open the TTS would be different. The duration or transition from 20°F to 113°F would be greater compared to 70°F to 113°F. The actual duration would be directly proportional to the delta T. The exact numbers, I do not know.

Tony

yea that's what I figured. don't think he said what his starting temp was.

I really have not had to do anything the CSV circuit that required any testing.

I am sub'd. This is interesting. I had no clue it could heat up that quickly. Thought it was all driven by ambient.

OP needs to state what the approx ambient was for a frame of reference.

there is another thread going on this that has good info on it.

it does not take much extra fuel or you could foul the plugs and flood it.

Hi Guys. OP here. My test was bench top and ambient at about 70 deg F. I also put the valve in the fridge for a while and got 3 seconds instead of two. Here's a really interesting part. I then heated the valve up with a hot air gun (too hot to touch). There was still a ground connection at W in this state. However, as soon a you energize G, there is an instantaneous opening of the switch, and so no power to the CSV.

My car is in my shop. Let me replicate your test.

If you post the link for the bench test I can replicate.

Two/three seconds just seems too short of time but I say this from ignorance. Would be a good exercise for me.

Sounds good Bob. I'll post the test link tonight. The original test procedure was set up and conducted by Tony and he actually got a 3 second result. I'm really curious to see what you get. It will also help me to understand if my TTS is potentially faulty. Thanks.

I don’t recall.........
 

997at,

I don’t know where you got the 3 sec. test result as far as I could remember, I was getting 6~8 sec. for the test light to come off. I don’t recall getting 3 sec. result. Another TTS arrived today and I will test it and share what I find.

Tony

You are indeed correct........
 

997at,


Just received today a TTS from another PP member. Good time to refresh my memory and I will removed the TTS in cars to test too.

http://forums.pelicanparts.com/uploa...1512008730.jpg

http://forums.pelicanparts.com/uploa...1512008730.jpg

You are indeed correct about the time TTS switched off. I was getting 2~3 sec. and repeated the tests after cooling them. My recollection about the 6~8 sec. duration is incorrect and you are right.

Tony

Tony, thanks for confirming the result. Looks like my TTS is good after all. I wanted to check because I pay close attention to your posts...I'm refurbishing my CIS, and almost everything I've learned about it came from you.

Hi Bob, here's the original test procedure that Tony posted a while back (post 28 in the thread). It works like a charm.

http://forums.pelicanparts.com/porsche-911-technical-forum/594010-thermo-time-switch-1978-sc-3-0-a-2.html

Thanks for the link.

I'm trying but I need alligator clips for wires....I think.

I am running into the same instantaneous shut off you experienced with less than optimal connections.

I can get it warm with juice running through it.

If I heat it up with a heat gun the ohms increase but not anywhere near an open circuit. Maybe 26 ohms when pulled out of the freezer to 40 ohms when I heat it up.

Will report back. Betcha when I get the rig set up right it will be just a few seconds.