testing the temp sensor 2

[airkooledchris]

so im sure everyone has ran into this themselves as well, but how in the hell do you test it properly?
2500 ohms at 65 degrees? great, but how do you know how close to 65 degree's it is?

what if it's hotter or colder, wouldn't the value then change?

I read the ratwell writeup, and im pretty sure ill just change it and see what I see, but ill share the results I got.

After seeing the requirement for it to be 65 degree's, I figured id just check it after the bus was shut off for a little while and I knew it should still be warm.

first test showed 710 ohms. I instantly thought OK, it's busted.
second test a bit later was showing 860
I ran it again later, and after a little while cooling down I got 1765 ohms.

how the hell is anyone supposed to test these things properly? did VW put them into some controlled temperature area and then run the tests at exactly 65 degrees?

[Westy78]

I've always removed mine and let it sit for a few hours to make sure it's at room temp.

[airkooledchris]

it doesn't need to be 'installed' to perform the test?

do you reinstall it before then testing, or just ground the 'sender' end?

[Westy78]

No it doesn't need to be installed. It's just a resistance test. Hook negative lead to one end, positive to the other and measure the ohms. Did you see the chart for different temps on Ratwell's site?

[Gypsie]

After you have tested it in a 'controlled setting', like say your house with the thermostat set to 65ish (let it even out but I think a few degrees either side won't matter too much), remember that even holding it will raise the temp a bit.

you might want to make sure that your installed readings aren't being affected by bad connection/grounding. clean out the mounting hole and the mating surfaces and tighten the sucker gutentight.


your readings suggest a connectinon issue (bad wire, bad ground, etc)

[Amskeptic]

Honestly, don't get too excited by every last ohm. Your adjustments compensate mightily for any variations. The most important function of the thing is to *change* value. Note that the factory has a generous range, a "window" of acceptable values.
Colin