Coolant temp sending unit.

[widowmaker77]

Got a question. I can’t get my coolant gauge to read. I’ve tried three different coolant sending units and none of them will read. I have removed the wire and grounded it out to verify the wire and the gauge are working gauge pegs out to hot. I don’t understand what’s going on. Motor is a 5.0 explorer efi sending unit for gauge a for a 77 bronco. Gauge cluster is original 66 unit that was refurbed by classy gauges. I ohmd the sending unit while it was in the motor cold. Ohms were like 330. So I checked an old one that was in my 77 302 and the ohms on it were higher. Like 350 cold. So I tried it and still no luck. Ohmd the sender hot and I’m getting like 19. Anyone have any suggestions?

 

[Broncobowsher]

A '66 cluster should have a '66 sending unit. But it should still read with a '77 sending unit, if not as accurate.

Thought... Are you using teflon TAPE to seal the sending unit to the manifold? That can act as an insulator. I've had far better luck with teflon PASTE on senders that ground through the threads. You get better metal to metal contact with the paste where the tape can isolate the metals and you don't get the ground.

 

[widowmaker77]

I was wondering if I needed to use a 66 sending unit.oil pressure unit is for a 77 also and it works. So idk maybe I do need a 66 sender. Currently It will
Not read anything with these senders I’ve been using. . Also I’m not using any thread tape.

 

[widowmaker77]

@Broncobowsher so I did a little digging on rockauto and there are two different part numbers for the standard and wells temp senders between a 66 289 and a 77 302. Wondering if the difference is the internal resistance and since I’m using a 77 sender that’s why I’m not getting a reading on my gauge.