Topic: Temparature ohm readings


jamesmundstock    -- 03-16-2020 @ 4:01 AM
  I am converting my '47 coupe to 12 volt and bought both sending units from one of the major Ford restoration suppliers. I can't get my gauge to read correctly. It depending how I connect the wires, it reads hot and switching it reads cold. The gauge never changes when the engine is running. I took the sending units out and checked the ohms. One read 0 ohms and the other read to infinity. The gauge I was hooked to was a remote gauge and not the one in the car. I would think both sending units should read the same. Any suggestions? Thanks in advance for any feed back.


40 Coupe    -- 03-16-2020 @ 5:14 AM
  The double terminal unit should read 0. ohms cold (not installed) and the single should also. When installed and the engine warm, the double terminal unit should stay at 0 ohms and the single terminal unit will open and close it's contacts to make the gauge (which reads "hot" out of the box) read the proper temperature. The only time the double terminal unit opens it's contacts is when the engine overheats. The single terminal unit needs electrical current to open it's contacts.


TomO    -- 03-16-2020 @ 8:59 AM
  The King-Seeley units in working condition both read 0 ohms when cold. I have no idea of the resistance reading of the aftermarket units.

The correct way to wire the sending units is to have the single terminal unit on the right side of the block and the 2 terminal unit on the left side of the block. The wire from the gauge goes to one terminal of the 2 terminal unit and the other terminal is connected to the single terminal unit. The gauge should read hot with the ignition switch OFF and coolant temperature with the switch on.

The gauges should have 6 volts to them, 12 volts will damage them.

Tom

This message was edited by TomO on 3-16-20 @ 9:27 AM


sarahcecelia    -- 03-16-2020 @ 3:19 PM
  Call Randy Rundle at the 5th Ave Garage , Clay Center, Kansas City ,Kansas to buy his resistors(1- for each gauge) when you use 12 volts on them!They are about $15 each.

Regards, Steve Lee


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