Random Post of the Day ( original post date 2021, March 19 )

1966 Ford Cold and Hot Lamp Temperature Trip Point

Hello all,

I was wondering at what temperature the COLD lamp extinguishes and at what temp the HOT lamp illuminates. Let me preface this with my results are a sample set of one, so take it with a grain of salt. I tested an original Autolite sender. A larger sample set, say 5 original functional old ones and 5 new senders should be tested and the trip points plotted for a better picture. But this gives a pretty good idea for now.

In a nut shell for this sender the cold lamp goes out at 117 ˚F and the hot lamp comes on at 244 ˚F.

If you're curious how I tested and that the numbers are accurate for that sender here's some pictures of my crude test apparatus.

Here's my test setup. I have a heated stir plate with cheap veggie oil. There is a stir bar mixing it. At the top there are two lamps; a blue and a red. They are the COLD and HOT lamps connected to the sender immersed in the oil. Sorry for the clutter, I am finishing up the factory clock overhaul for the XL and preparing to overhaul the factory AM-FM stereo radio for the XL.

Better view

I figured the COLD lamp would go out around 100 or so. So I went up to 90 quickly, let it stabilize since the sender has appreciable thermal mass compared to the type K thermocouple. Then I slowly increased the temp till it went out.

Same with the HOT lamp. I figured around 230, so I quickly went up to 230, let it stabilize and then slowly increased till the HOT lamp lit.

For those wondering, well how do I know my meter is accurate and kudos to those who do wonder.

This is an ASTM 2C accurate to 1 degree and this particular thermometer is NIST certified.

We can call that accurate enough for this test.

The ice point is close. I should be using crushed ice in an insulated container, but I'm out of Styrofoam cups and I was too lazy to crush the ice. It will read a few tenths higher as a result.

Cheers.

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