Temperature gauge always hot?

[somatdad]

I just need some verification regarding my temperature gauge in the 55 Ford Wagon. I have done some rewiring and a 12 V conversion. I have a reducer for the gas gauge and temperature gauge. The voltage to the gauge is a steady 5.6 volts. Now as far as I can tell from my searches, it seems as if the temperature gauge is supposed to start off with the needle pointing to the hot side of the gauge. Which seems backwards to me, but....it appeared to be working fine until just the other night, when the needle never moved from hot. Is that normal and how do I check to make sure this thing is hooked up correctly?

I had tried to mark the wire locations accurately but mistakes are possible. Does it make a difference what side of the gauge the hot wire is attached to?

I would think that when I turn the key on it should move to the cold position and then register hot as the car warms up. Your thoughts would be appreciated.

Thanks.

[toby]

Reverse the wires and try. In my 51 F1, I had to reverse the direction of the wire that ran through the loop on the gauge.

[somatdad]

Tried that. Still pegged to hot.

[Daves55Sedan]

Yes the wiring must be properly connected for the guage to work ,
facing the backside of the guage, connect the blue-green wire to the terminal on the right. Connect the red-white wire to the terminal on the left.
the blue-green wire is the "hot" wire in the circuit. Use a 12volt lamp tester to determine if power is available. The other end of that wire should be connected to the accessory terminal of the ignition switch.

[somatdad]

Well the first time I switched the wires on the back of the gauge it was stilled pegged to hot. However, I gave it another try and it seems to be working, I think. At this point I'm still suspicious of the sending unit. Thanks for the tips.

One last thing, theoritically when I turn the key on and the car is cold the temp gauge should move all the way to cold correct? as of now it moves but barely halfway.

It's too cold and rainy outside now so I'll remove the temp sensor next week to test it . I'm a pansy when it comes to the cold and rain, looking forward to warmer weather.

[Daves55Sedan]

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When you turn the key on, the guage should reflect whatever the water temperature is at that time.
Thus, if the engine was shut off for a couple of hours, the water temperature might still be pretty high and not cool enough to send the needle all the way back to "C".
But if you are sure the water should be cool, it should go all the way back to "C".

[somatdad]

Been celebrating my anniversary for the past three days out of town and thinking about this silly temp gauge. (don't tell my wife).

I agree with Daves that my temp gauge should reflect what my water temp is.

However, this is what it does, (it was the first thing I checked when I got home today).

I turned the key on, (and it's cold outside 40 degrees or so) the needle stays at hot. It does not move to cold where you would think it would go. However, If I start the car and let it run and warm up, the temp gauge registers a lower temperature, in the center of the gauge where it should be. I am just wondering why it doesn't immediately register cold.

I would just like to have a little confidence in that gauge/temp sensor so that I am sure my engine is running properly.

Any thoughts about the above scenario.

[Dominic Hide]

I am betting that you changed the temp sender when you did the 12v conversion. If so then that is your problem. The '55 gauge has to be used with a pre '56 6v sender.
Also for what it is worth, the wires don't care which post they are on, and also as long as you are using the original gauge and sender there is no need for a voltage regulator. Both the temp and fuel gauges will work fine on 12 volts.

[somatdad]

The sender came with the car, I'm not sure if it's original or if the previous owner changed it. I have a voltage reducer on the instrument cluster so that 5.6 V is going to the gauges.

Can you find a pre 56 sender at your local parts store? Or do I need to search the internet?

[Dominic Hide]

The correct sender should look like this...(but without the 12v stamp)



All senders from the flathead era through the '55 model year are the same and will work. They may not be available from regular parts houses but any of the specialist shops that cover Thunderbird or early Fords should have them.
The only other sender that looks like this is for the '56 models (pictured). Do NOT be tempted to try one. Although it is 12volts it uses a much higher ohm resistance and will burn up your gauge.
The later senders are much smaller and require the regulator that you are using to work. If this is what you have then your gauge is working correctly, just backwards.

[somatdad]

The sender I have looks just like your picture. I just talked to the previous owner and he can't remember if he replaced the sensor when he rebuilt the motor 6 years ago or not.

When I check this sensor with my ohm meter it gives me all sorts of readings so I'm not sure what the heck is going on. I certainly don't want to mess up my gauge.

[Dominic Hide]

Have you removed the sender from the head? If so does it have a long fluted tail like the one pictured. If it has the same threads and and large hex, 5/8 wrench, but with a short tail then it is from a '57 6 cylinder engine and will work just like the ones mentioned in the previous post. ie backwards.

All pre '57 senders have a tiny set of points controlled by a bi-metallic strip inside that tail which open and close when any power is applied. This makes it impossible to measure resistance.



You can however check the resistance of the gauge. It should read between 11 and 14 ohms depending on condition. If it reads 40 ohms then it is for a '56 and will only work with a '56 sender.

[somatdad]

I did not take it apart, did not even know I could. I think i will buy a new one and see what happens. Details, details, details. Thanks for the tips.

[Dominic Hide]

That last picture was just to show what was inside. I would not recommend taking one apart. Just removing it from the head and seeing the length of the tail will let you know what you have. I will take pictures of the different senders when I get to the shop tomorrow and post them here for comparison.

[somatdad]

Thanks. I won't have time to get to the store for the next couple of days anyway.

[Dominic Hide]

A day late, but here is the picture...



From left to right...
'55 and earlier, works with "rest on hot gauge".
'56 one year only, " " " "
'57-? 6 cylinder. Fits same thread boss as earlier cars but requires voltage regulator.
'57 and up v8. Smaller thread boss and hex. Also requires voltage regulator.

[junkyardjeff]

The temp gauge on my 55 wont go all the way to cold when started cold and I have a IVR from a 60s truck to drop the voltage so I might try another IVR to see if thats the problem.

[somatdad]

Dominic thanks for the photos. Unfortunately my temp sensor does not have a handy 6V stamped on the side of it. It does have the numbers 233 stamped on it. Of course after I take it out of the motor, take a picture and put it back in real quick i notice you are so much smarter than i and you did yours on graph paper to show size. Oh well, maybe this will help. However, I think it looks more like the 12 V than the 6 V, what are your thoughts?

And Jeff sounds like your temp gauge does exactly what mine does. My IVR is putting out 5.6V to the gauge so I don't think that's the issue. I still wonder why it doesn't go to cold.

[rick55]

The description you give of your gauge's behavior suggests that the polarity is incorrect. The 55 was originally +ve earth and I presume you now have it wired -ve earth. I know it has been mentioned that polarity does not matter with these gauges but I would give it a try. Swap the connections on the temp gauge and see if it makes a difference.
It seems like you have done everything else right, so what have you got to lose.
If it still behaves the same you know once you make sure that you have the correct sender, it can only be that the gauge us faulty.
Macs sell new gauges but they aren't cheap.
Regards

[Dominic Hide]

Since your sender is not marked with voltage it is almost certainly 6v and original. There was no need to mark them before 1956 as 12 volt was not yet in use and there fore nothing to be confused with.
Unfortunately this means that my theory of miss matched parts goes out the window and you still have a problem.
I have seen many bad senders but none that behaves as yours does. Working, they go to cold when powered up, and not working they remain on hot and never move, yet you say yours moves from right to left as the engine heats up. I have to believe that the gauge and sender are correct and something about the voltage reducer is some how affecting how they work. When Ford started using instrument voltage regulators in 1957 they were wired with power coming off ignition switch to the ivr and two wires off the ivr to the gauges. Is this how you wired yours? If so is the gas gauge also working backwards? Assuming you are using a Ford type regulator, is it grounded by being bolted to the back of the instrument cluster, and not just hanging back there? Either way if it was my car I would take the regulator out of the system altogether. As I said earlier as long as the senders and gauges are original type parts they will work fine on 12 volts. I know this goes against conventional wisdom on these forums but I have done 3 or 4 of these conversions every year since 1984, mostly '55 Thunderbirds, and have never used one.

[somatdad]

Well I found a fellow here in Salem, Oregon, Wagers Ford Parts, that had an NOS 6V Sender. Put it in, turned the key and off to cold we went. I appreciate everyone's help. It was a weird.

Happy to have a temp gauge that now climbs as the car warms up.

Jim

[junkyardjeff]

I have a reproduction sending unit on mine so maybe time to look for a NOS sender,I put a NOS gauge in and it worked correctly the first time but back to the way it was before.

[48 fordor]

OK, I have been looking at all kind of info on 12V to 6V gauges for my 55 ford. My ford on 6V the temp gauge starts on H, start the engine, it drops to C, then swings toward H. To H indicating the engine is too hot. I have converted to 12V neg ground and used a high quality voltage reducer made for gauges. I reversed the connections at the back of both gauges. Fuel gauge works fine. The temp gauge still acts the same. I replaced the sensor with a sensor (that was new) that I removed from my 48 flathead. I have a new radiator, thermostat, high flow water pump & fan. Sensor ground is good. I have a IR gun and see nowhere on the engine or radiator that it is running too hot. What next, the gauge?

[junkyardjeff]

When my 55 had the original motor the temp gauge ran almost all the way to hot with a 180 thermostat and its the same way still,I do not think the gauge is very accurate.

[48 fordor]

Sounds like what I get out of this is watch the gauge and keep my IR gun handy. Replacing the gauge is around $80. Looks like that might be a bad waste of $$. I'll see if it bothers me too much. I really don't want to add under dash gauges that I have.

[dmsfrr]

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Read this linked article, it says that the oem '55 gauges are not voltage or polarity sensitive. It's due to the old-school way those gauges were built.
And, in most cases a voltage reducer is not needed.

The oem temp and fuel gauge parts are usually not all that compatible with newly made replacement style parts. The (pre '57) oem gauges and their sensors like to work as a pair, with original yr matching parts at both ends of the circuit.

https://www.ctci.org/gilsgarage/6to12.php

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