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Discussion Starter · #21 ·
Boiled a glass of water and checked it with a thermometer and it was roughly 207 degrees. When I checked my 203Z TSU5 which was 6$ from advance auto.

I placed the sender in water with the top out of the water.
I checked many times by putting one probe on the engine end and the other on the connector spot.

The lowest reading I could get was 104 Ohms.

Does this mean I got a bad one and I should try another of the same type?

That the model is no good?

Or did I measure it wrongly?

thanks for all the help
jim
 

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To get an accurate reading the sender must be in a rolling boil for at least 2 min. Make sure your meter is zeroed (or minus your lowest setting).
 

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Discussion Starter · #23 ·
Just lower the radiator about 1/2 way should be good.

The connector isn't what makes the sender,Autozone has thumbtack conn sender # TU5 that has the same poor readings as the LL senders.

So far (knock on wood) the WT203 has been consistently good.
After finally going through a few sending units, I gor this specific WT203 sending unit and it appears to be working great. Last night with the temperature outside at 95, it showed as 230. Which is a lot better than what I was getting from other brands, which was 150 max.

Also, in case anyone wants to know. You can replace your sending unit, with just minimal leakage while the coolant is in the car. I just tried to be quick and had a towel down to catch spillage.
 

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Another quick and dirty test for a gauge is with a testlight. An 1894 bulb hooked in place of the sender will run the gauge to about 1/2 scale.

I take the radiator cap off, put it back on, and change the sender. Usually lose about 1/2 cup of antifreeze if you're fast. On an electrical sender, anything you put on the threads will insulate the sender from ground so that will affect the reading.
 
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