Temperature sensor or
 

Hello
Has a problem with the temperature of a Ford flathead 1953. When the ignition is switched on, the temperature gauge is hot (it should be or?). When the engine is running then it falls to cold. Could it be the temperature sensor on the right half that does not work? Is it possible to measure it in any way?

Re: Temperature sensor or
 

First of all to clarify things, are you referring to the sensor with one terminal or two terminals ("left" and "right" can be confusing)? I had a similar problem with my car, so I removed the one terminal sensor and "ohmed it out" with my multi-meter. I then checked several extra sensors I had and the readings were quite different. I swapped out the sensor and the gauge started working properly again. I don't remember what the readings were, as this was several years ago. Perhaps someone else here has the proper readings. If they don't, let me know and I'll check a known good sensor when I go to my shop.

Re: Temperature sensor or
 

Thanks tubman. it would be nice if you could get that data especially the resistance through the temp sensor when the engine is operating temperature. If that is the fault, is it then that the temperature gauge behaves? The temperature sensor on the left side with two connections is only a switch on and off. (When the ignition is switched on, it sends power to the right temp sensor) I have understood this right then.

Re: Temperature sensor or
 

Not sure you would see any ohms difference between cold and hot. The coil in the temperature sensor is to heat the bi-metal strip that opens and closes a set of points. The sensor is a pulse type of device with the opening and closing of the points (vibration rate) controlling the current to the gauge. Ford does not list checking resistance as a trouble shooting method for checking sensors or gauges. You can check a gauge with a small battery (like a D cell) to see if you get a needle deflection. 1 1/2 volts should give you about midpoint on a gauge. Ford used a variable resistance test device.

Re: Temperature sensor or
 

A reading in the range of 12-14 ohms usually indicates a good temperature sender. I have seen some as low as 9 ohms that are still good.

Hope this helps.

Tom

Re: Temperature sensor or
 

Thanks to both of you. It seems that you do not get too far to measure it either :-). Does anyone have experience of how the temperature gauge behaves if this temperature sensor is broken? Is it that when the engine gets warmer, does it fall and continues to fall until it shows cold? How did old Henry think when he let the temperature gauge start on hot, at last, was never the cold part used? Or I've missed something. Tom, I'll check what ohm says tomorrow if the weather permits,
Thank you once again
Lars

Re: Temperature sensor or
 

Thanks to both of you. It seems that you do not get too far to measure it either :-). Does anyone have experience of how the temperature gauge behaves if this temperature sensor is broken? Is it that when the engine gets warmer, does it fall and continues to fall until it shows cold? How did old Henry think when he let the temperature gauge start on hot, at last, was never the cold part used? Or I've missed something. Tom, I'll check what ohm says tomorrow if the weather permits,
Thank you once again
Lars

Re: Temperature sensor or
 

An open displays hot, as would be the case with the double terminal sensor opening up. Likewise if the single terminal sensor points are open the gauge will show hot until the points initially close and start the pulsing cycle to read a temperature consistent with the pulse rate. What does a bad sensor look like, no idea! :)

Fords suggestion is to try a know good sensor to determine if it is the sensor or the gauge, so there you go!!!

Re: Temperature sensor or
 

Hi again so the double sensor should not power out just after switching on the ignition? That's what's happening here on this engine. It then feeds the seed with a pin. By the way, I connected the ohm meter to the single sensor. I started reading when the engine was hot and the temperature gauge was cold. 17.8 ohms after the engine is still standing so after about 10 minutes I can read 18.6 Ohm. So when the engine is cold you can read 24.4 Ohm. It does not tell me anything. Anyone who understands these values?
Now I start thinking about the second dual-sensor transducer. Can it be wrong when it sends power at once as soon as the ignition goes on.
I would also like to try another sensor but here are not many flatheads on the streets, Should I buy new, it will be from you in the United States and they are not cheap to get here to Sweden but it's possible that this story will end .
Sunny greetings from Sweden to you

Re: Temperature sensor or
 

Either unit can be tested in a pan of water with a hot plate using an Ohms meter on the two terminal unit to see if it opens the bimetallic switch at high temp or rig the single terminal unit with a long jumper to the gauge wire to see if it gets a temperature reading that compares to another thermometer in the heated water. The single terminal unit's body needs a common ground with the battery but the two terminal is just a temperature sensitive switch. It's either open or closed to current flow depending on the temperature it's exposed to.

It sounds to me like there is an intermittent open circuit there when you start. If the circuit is open or the switch is off the gauge indicates hot.

Re: Temperature sensor or
 

The ohms readings change because of the temperature difference of the wire in the coil. Just like a ballast resister does. Might be interesting to check, but not sure it tells you much of anything. Again, these are not resistance devices, they operate on current pulses generated by the rate the points open and close.

Re: Temperature sensor or
 

Lars
can you find a different temp sensor? On the bench the readings should be in the area of 12-14 ohms. Start with a good known sender unit and then we can go from there.

I can send you one if you can't get one in Sweden.

Tom

Re: Temperature sensor or
 

Ok guys I have now ordered a new temperature sensor but only one with one connection. Right. I'll have to wait for it and will return when I change it and get the result.
New problems now show up in the sky. Today, suddenly, the carburetor began to flow over when I started it as usual. There must be a simpler template to cut for the setting of the fleet. Anyone who knows such? Have also read somewhere that it may be the original gasoline pump that delivers too much Psi. Should it be about 2.5 psi in to the carburetor? Or is it just as I read.
Thanks for now. I am now waiting for the temperature sensor :-) hope it will help me with one of the problems
Lars

Re: Temperature sensor or
 

What type of sensor did you order, NOS/used or a modern replacement? If it's a modern sensor you will be changing technology as it will be a resistance device, not the original current pulse type. I know on the fuel level sensors this can be an issue, but don't know about the temperature sensors. A resistance sensor will not provide the same input to the original gauge and it will read differently than it would with the original sender. This may not be that big an issue as the gauges are just a rough approximation to begin with. Be interesting to see how it works out.

Fuel pressure should be around 2.5 psi.

Re: Temperature sensor or
 

An NOS can only be forgotten here in Sweden. I was just lucky to get a modern sensor. Obviously, it's probably Made in China but I'm chances there's no other way out. Should also check fuel pressure. Thank you for your information on the pressure
After switching the sensor, I enter what happened or did not happen.
The China Sensor cost me 890 SEK about $ 106

Lars
It's expensive with old cars but who has said it should be cheap. :-)

Re: Temperature sensor or
 

Lars

If you read thru the posts (3 back) I offered to send you a temp sensor. I was only trying to help as I am interested in the old car hobby.

Hope you solve your problem.

Tom

Re: Temperature sensor or
 

Depending on his results Jersey Devil he may still be looking for a NOS sensor!! :)

Re: Temperature sensor or
 

You are probably right and If that happens I will still make the offer.

Tom

Re: Temperature sensor or
 

I saw your invite Jersey Devil and I thank for it. But now I have to work well summer is short here in northern Sweden :-). But just because I ordered a sensor, it is not said that I will not use your kindness. But for the moment, it has not come, but I have been notified that it is on its way.
So we'll have to wait and see, nothing will happen this weekend, as the mail will not arrive at the earliest Monday. So it may be like Jsery writes everything depends on the result.
Have a nice weekend
Lars

Re: Temperature sensor or
 

Hello again
Today, at last, the temperature sensor came and the best thing about it was that it was made in the United States. As I wrote in a previous post, it was expensive. But now everything works as it should. So again, thanks for the help of all involved. Then we finish the thread with the roaring temperature gauge.
Mecury 53.