| Thomas1940-V8 | -- 04-02-2019 @ 6:47 AM |
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I need your help. I'm from Germany and about to fix my temperature gauge in my 40s Ford Deluxe. For the analysis, I need the characteristic from the right temperature sensor in the cylinder head. Does anyone have a resistance value in ohms at room temperature (20 ° C in Germany) and maybe at 100 ° C (boiling water)? Regards Thomas
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| TomO | -- 04-02-2019 @ 7:52 AM |
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The resistance value of the original temperature senders is constant at all temperatures. The sender with one terminal contains a set of contact points, one of them is a bi-metal strip that is heated by a coil of wire wrapped around it. The other contact is mounted on a bi-metal strip that is heated by the coolant. The coil heated strip has current flowing in the coil when the contacts are closed causing the dash unit bi-meal strip to move the gauge towards cold. The coolant heated strip moves away from the coil heated strip as the coolant warms up causing the dash needle to move towards hot. The double contact sending unit is just a hot switch. The contacts remain closed except when the coolant is hot, then they open and the gauge moves to hot. The resistance should be close to 0 ohms at all temperatures on both types of sending units. The current flow in the single terminal unit and gauge will decrease as the temperature rises. A quick test of the dash unit is to turn on the ignition switch. The gauge should move towards cold, if it doesn't ground the wire going to the single terminal sending unit to see if the gauge moves to cold when you turn the ignition switch on. If it still shows hot, ground the wire from the gauge to the double contact sending unit. If it moves to cold, the gauge is OK, if it stays on Hot, the gauge is bad. If it moves toward cold the 2 terminal unit is bad. Some of the aftermarket sending units are resistance type units and I do not have the specifications for them. If you have any more questions, please come back and we will try to answer them. Tom
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| Thomas1940-V8 | -- 04-03-2019 @ 8:50 AM |
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Hello Tom, Thank you for the very detailed information. Now I know that in my V8 right side there is a wrong temperature sensor installed. It has approximately 2KOhm when cold and approximately 200 Ohm when hot (Type NTC). So the temperature display is always HOT. The left temperature sensor I had just bought new (NOS) and renewed. I have already ordered now a right NOS temperature sensor in the USA. The instrument is ok. I tested it with ground. Today I connected a 2000 ohm potentiometer instead of the right temperature sensor. Then, with the ignition switched on, I turned the potentiometer until the temperature display was once at hot and normal temperature. In both cases I then measured the set resistance without ignition. It gave 14 ohms at normal temperature and 20 ohms for hot temperature. So that would be a value that I would have to measure approximately at the right temperature sensor? Regards Thomas
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| TomO | -- 04-04-2019 @ 9:16 AM |
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The original sending units are very sturdy and reasonably accurate. They do not fail often. I have heard that the sending units sold today use a change in resistance to indicate the coolant temperature and are not as accurate as the original King Seeley type. Here is a link to a King Seely unit on E-Bay. It is the same as would have been in your engine when it was delivered new. https://www.ebay.com/itm/39-48-Ford-Lincoln-Mercury-engine-water-temperature-sending-unit-NOS-40-41-42-4/382592957908?epid=1023781997&hash=item5914513dd4:g:EtsAAOSw3qRbxN5V:sc:USPSPriorityMailSmallFlatRateBox!40514!US!-1 Tom
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