2-wire IAT measures open ckt @ room temp

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2-wire IAT measures open ckt @ room temp

Postby 9secz » Wed Jun 06, 2012 7:48 pm

My car has the IAT shown in the following pic. I thought it was broken because the resistance measures open circuit at room temp. I bought a new Standard Motor Products AX24, which is very close to mine, but it also measures open circuit at room temp. Both of the them will jump from OL to somewhere in the 500 Ohm neighborhood when I blow my heat gun on them. The resistance drops from there as they heat up. The resistance climbs again as they cool off, then jumps abruptly from 500-ish to OL when they get close to room temp. Both of them have a 2-wire interface that uses an EV1 fuel injector connector.

What sensor technology do you think they use, and can I use one of them with my MS3?

Image

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Re: 2-wire IAT measures open ckt @ room temp

Postby SymTech Laboratories » Wed Jun 06, 2012 8:09 pm

Are you sure your multimeter/ohmmeter is set to the correct range when you're measuring the resistance of the sensor?
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Re: 2-wire IAT measures open ckt @ room temp

Postby 9secz » Wed Jun 06, 2012 8:14 pm

SymTech Laboratories wrote:Are you sure your multimeter/ohmmeter is set to the correct range when you're measuring the resistance of the sensor?

It's autoranging.

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Re: 2-wire IAT measures open ckt @ room temp

Postby Matt Cramer » Thu Jun 07, 2012 5:28 am

That may be some sort of thermoswitch for an emissions control gadget.
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Re: 2-wire IAT measures open ckt @ room temp

Postby 9secz » Fri Jun 08, 2012 12:48 pm

One of my fellow EEs always said, when a measurement doesn't make sense, don't trust the metrology. A new DMM battery fixed this flaky measurement.

Let's just call this one operator error and move on. :oops:

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