Help with temp sending unit

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Hope someone here can help.
Found the temp sending unit in intake manifold wasn’t showing ground to my relay connected to electric radiator fan relay. Manually connected a ground and the fans turn on. Replaced the unit and when it’s up to temperature I can see 0 ohms to ground. But the relay doesn’t turn on. When I connect the new connector for the temp sending unit to ground with an alligator clip to ground in the manifold the fans turn on. Which must mean the wiring for the sensor is okay. But I can’t see what’s the difference.
If anyone has experience with this please let me know where I’m going wrong!

[dmjlambert]

I suggest show a diagram of how you have the relay and temp sending unit wired up. Hand-drawn diagram would be fine.

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That makes sense, will do that and take some photos. Thanks!

[PbFut]

First, the device should be a temperature switch not a sending unit. Assuming it is a switch and not sender unit check the following.
Check that the housing of the switch is actually grounding to the manifold. Teflon tape or pipe dope can insolate. Given wire activates relay when manually grounded, the problem is the switch in some way.
Wrong device, not properly grounded switch, or not connecting to wire correctly.

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Originally Posted by PbFut

First, the device should be a temperature switch not a sending unit. Assuming it is a switch and not sender unit check the following.
Check that the housing of the switch is actually grounding to the manifold. Teflon tape or pipe dope can insolate. Given wire activates relay when manually grounded, the problem is the switch in some way.
Wrong device, not properly grounded switch, or not connecting to wire correctly.

I checked that the body of the unit was grounded. Ohm meter between housing of the unit and manifold bolt is a dead short, 0 ohms. Likewise when up to temperature the center pin shows ground, 0 ohms between center pin and manifold bolt. There is Teflon tape, and thought perhaps that was causing an issue. Will post part number, but you are certainly right the device is a switch.

And unless something else is going on you must be right, I’ve must have somehow messed up the connection between wire connector and the pin of the switch.

Thanks for the reply!! I’ll submit a photo of what I have and when I figure out what I’ve messed up I’ll share that as well 🙈🙉

[HO455]

Please disregard that old internet wives tale about Teflon tape its been disproven numerous times.

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Originally Posted by HO455

Please disregard that old internet wives tale about Teflon tape its been disproven numerous times.

Turns out I can attest to that. The threads must have “cut” through. Although I can see how if over done it could cause a problem. But alas nothing so simple for me this time.

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Originally Posted by PbFut

First, the device should be a temperature switch not a sending unit. Assuming it is a switch and not sender unit check the following.
Check that the housing of the switch is actually grounding to the manifold. Teflon tape or pipe dope can insolate. Given wire activates relay when manually grounded, the problem is the switch in some way.
Wrong device, not properly grounded switch, or not connecting to wire correctly.

I looked up the part number, and it’s a temperature sending unit. It goes to a short to ground on my multimeter when at temp. But doesn’t work, so I ordered a temperature switch. It comes in Wednesday. If that does it will let you know. Thanks much either way!