Can someone please test a known good new or used cylinder head temp sensor with a multimeter and tell me if they have electrical continuity from the base to the tip of the electrical connector? Thanks in advance!

It should have resistance, but continuity. Resistance drops with heat.

This year I've seen a couple of these fail in only a few months.

Thanks for your prompt reply.

That is what I thought. I have been plagued with a "no start" condition for about 6 weeks now and have recently installed a brand new Bosch CHT sensor. It apparently was no good right out of the bag as I am still not able to start my car due to a rich condition. I think it is because the CHT sensor is bad.

So, is the following statement true or false?

With no continuity at the CHT sensor, the fuel injection brain sees infinite ohms of resistance and richens the mixture so much that the car will not start.

Maybe to get you started you could install a variable resistor from Radio Shack that would have resistance of the range needed to start then you could decide whether or not the CHT sensor was faulty or not.

How the ecu interprets an open circuit, I don't know, but with my '76 2.0 an open circuit would stall a running engine and prevent restart. The sensor should be about 3k ohm cold and a few hundred ohm hot. Verify that, as there are variuous causes for a rich condition, if that's what you have.

Yup, no continuity makes it super rich. Install a 300 ohm resistor instead as a 'shortcut' or tester. The car will run a little rough while cold, but once it warms up it'll run normal.

That particular thermistor will read 7373 Ohms at 0C, 2252 Ohms at 25C, and 154 Ohms at 100C.
They will read an almost dead short (close to 0 Ohms) at 190C (300F).

So Mcmarks suggestion is correct, it will think it is always warmed up

My car is a 1976 2.0 and my engine died at an autocross and I have not been able to restart it.

It is about 85 degrees F in my garage right now and I have about 2200 ohms resistance but no continuity. I will replace this new but bad sensor and then see if I need to add any additional resistance to the circuit.

Thanks for everyone's responses!

If your reading 2200 ohms you have continuity.

OK, now I am confused.

I must not be using my multi-meter correctly because I can measure ohms resistance, but not continuity, on the CHT sensor that I removed from my engine (thinking it was bad). To measure ohms resistance I set the multi-meter switch to ohms, touch one probe to the base of the sensor and one probe to the metal electrical connector at the end of the wire. I get about 1900 ohms resistance and this number continues to decline as the warmth of my hand warms up the sensor. I turn the switch on my multi-meter to check continuity using an audible signal, I position the probes like I did to measure ohms resistance, and I get no audible signal. When I touch the multi-meter probes together I get the audible signal. Am I doing something wrong?

I appreciate everyone's responses but it would be great if someone could please test a known, good CHT in this manner and share the results. Thank you.

You are doing nothing wrong. Continuity and resistance are two different electrical terms. Not the same.
Tom

Your using it right. I just don't think you have your head wrapped around what an ohm is. An ohm is a unit of electrical resistance. A perfect circuit has 0 ohms resistance. An open circuit (read no continuity) has infinite ohms of resistance. At 1900 ohms you have a circuit (read continuity) with 1900 ohms resistance.

Your multi meter must only give you an audible signal on a low resistance circuit.

"Continuity" can vary in meaning.

It typically means less than 1-5 Ohms.
But if you are looking for megaohms, then 2200 ohms might mean continuity.

Continuity means is there a complete path for electron flow in the circuit you are measuring. If the circuit is greater than XX ohms ( a preset value in the continuity setting), you don't get an audible signal. Not getting an audible signal does not mean you don't have continuity, just that the ohmic value of that circuit is above the preset value for a continuity check.
You really should not be using your meter to measure continuity of a circuit that is known to be 100 ohms in value or greater. That setting is most often used to measure from pin x in one plug to pin x in the plug on the other end to see if the wires are correctly installed in the plugs. Typically this would be less than 1 ohm. If the wires are correct, you get an audible signal. If no signal, you go back to check why not. Also used as a quick check to see if a diode is good or bad.
When using your meter to check circuits that you know will have some amount of resistance, always use the ohms setting.
You would do well to familiarize yourself with Brad Anders D-jet info. There is a link to that site on here somewhere, probably under 914 Info - top right of the page. Some very good info!!
Tom

Now I understand. Everyone's responses are much appreciated.

toadman, I had the exact same findings as you and kept telling myself that the CHT sensor in the engine was fine and within spec - and it actually was! Then, after further frustration, I decided it was best to simply replace it with a new one, to totally rule out the CHT sensor. Guess what, that was the only thing I had changed and it solved my issue.

One thing that I did discover afterwards, when bench testing the old CHT sensor that was originally in the car with yet another new one, was that the ohms value was slightly lower on my original one (by 500-600 ohms). I also noticed that my original CHT was a bit corroded so I have to wonder how corrosion effected the sensors ability to quickly communicate it's temp findings. These sensors are so cheap ($16 from Pelican) that it's worth just replacing them to freshen them up and rule them out.

Best of luck to you!