Technical Help needed with temp sending unit/dash gauge

Hello, friends. I have a '54 Ford Crestline Vic. Have been having trouble with the temp gauge at the dash. The car has been converted to 12 v. I have noticed that the temp gauge doesn't seem to be reading correctly. When the car is turned off, the gauge needle will go to rest on the hot side. When the car cranks up it goes to the cold side. I've heard that this is correct. What is happening is once the car gets up to running temp, the needle just keeps on rising all the way to hot side. So, I ordered a new 12 volt temp unit and put it in. Same prob with new 12 v . The car isn't running hot. I've used my temp gun on it many times. I have just ordered a 12 v to 6 volt instrument reducer. Is that what might be happening, not reduced? The previous owner told me that there was no need to put a reducer on the gauge ( I think he's wrong). I'm confused but wanted to see what you all might think to get me going correctly. A pic of old and new temp units attached. Thanks!

 

Yes, you need the voltage reducer. The previous owner told you wrong.

 

Use the stock sender that matches the gauge and reduce the voltage input to 6v as stated above.
Those gauges were never super accurate, but will at least alert you to any changes in temp.

 

Ok. So I didn't need to spend the money on the 12 volt sender? It's gonna need the 6 volt sender along with the reducer? TY!

 

Read all this temp. sender info. including links BEFORE you do anything else.
https://www.fordbarn.com/forum/showthread.php?t=221846
YES. You do need to reduce from 12 to 6 volts the voltage going to the temp. sending units.
Correct. You didn't need to spend the money on the 12 v sender unless you were going to
use it with the matching 12V gauge. Then it would work.

 

general rules of thumb for any electric gauges:

1. The sender has to match the gauge.
2. The gauge needs to get the supply voltage it was designed for.

 

Thanks for that info. I understand it now.

 

I have to re-do my gas tank soon. I was going to have it boiled and possibly sealed. Would I be ok with replacing the sending unit with the original style that is on the car currently? My fuel gauge seems to work fine.

 

if it's working, why would you replace it?

 

great point. not sure if it's original or not so I was just curious since Im gonna have the tank off anyway.

 

I wonder why the gas gauge is seeming to work fine without a reducer at the gauge unlike my temp situation. Any thoughts on that?

 

one thing I've learned over the past several years, is that old original stuff that still works, is worth keeping on my cars.

 

I don't know. Did you look for a reducer? maybe someone already installed one, and you didn't notice it?

 

I have looked behind the instrument panel and see no evidence of either a gas volt drop or a temp drop. Makes me scratch my head on the fuel side. should I just leave it as is or still put a reducer on that gauge as well? Again, this is all a learning curve to me but I appreciate learning from people who know.

 

Squirrel is correct. Don't mess with it if it's working. The original 1954 Ford fuel gauge and sending unit were 6 V and were matched units made by King Sealy. Be sure to remove the OEM fuel tank sending unit BEFORE you send tank out for cleaning.

They are very delicate, very expensive, super rare and very easily damaged. It is held in the
tank by 6 small machine screws and looks like this. Take very good care of this unit as there are no replacement parts except for the float. If you buy a replacement tank, be sure that it has the matching holes for locating the sending unit screws.
Have you read completely ALL the info. contained in the previous posts?

 

I would test the voltage at the gauge, using a hand held volt meter (DMM). It will either be 12v, 6v, or maybe it will fluctuate between 12v and 0v, if it has a thermal voltage regulator in the circuit.

Some 6v gauges will work on 12v, but you won't really know without doing some testing.

 

Peruse this info.
https://www.google.com/search?q=can...ome..69i57.16775j0j4&sourceid=chrome&ie=UTF-8

https://www.earlyfordv8.org/forum/printthread.cfm?Forum=18&Topic=5561

 

One thing not covered on your Temp issue. The sender is designed to ground on contact. A bad ground can cause gauge issues. Using to much sealer will do that. They are pipe thread and made to seal when tight, it only takes a touch of pipe sealer. If you wrap the sender with several layers of Teflon tape you just insulated the sender from ground.

 

really? I've never been able to insulate pipe threads by using teflon tape...the tape always seems to move out of the way, in several places, as I tighten the fitting.

 

Thanks Wizard. I can say that when I replaced the 6 volt temp sender with the new 12 v, I did NOT use any sealer or tape. The 6 volt that I removed had no signs of sealer that I could see.

 

Thanks, 19Fordy, I appreciate that info and have looked at it all and will no doubtly read again. I am SO glad you suggest being careful with the sending unit and I will be given your warnings. Like I say, I see no signs of a volt reducer at either the fuel gauge or the temp gauge. Gas seems to read ok it's just the temp that runs up to hot with actually running hot. I sure do appreciate all of the tips on this stuff.

 

If the gas gauge seems to be working without a reducer think it ok to leave as is or safe side it and install a drop on gauge?

 

The attached pic is the reducer I got from Speedway parts online

 

that looks like an LM7806 voltage regulator, mounted to a small PCB to make it easy to use. It should work fine for you.

Ford used a thermal voltage regulator when they went to 12v starting with 1956 models. I've used the stock 1970s replacement part to successfully convert 6v gauges in a 1955 Tbird to 12v.

 

You have a pic of what those look like, squirrel?

 

I also saw this type available but the one from speedway looked more solid. Are these ok to use?

 

maybe it's from the 1960s... it works just like an old turn signal flasher can...heats up, breaks the circuit, cools down, closes the circuit, etc. The average voltage is 6v, but the actual voltage is either 0v or 12v. The gauges have very slow response time, so it works. But again, not sure if it will work on a 54, I've used it on a 55

 

Squirrel, your an exception to all rules cause your Smart enough to know what just enough is. Some think more is better in all cases.

 

Hmmm, never seen that one before. you think I'd be ok without one on the fuel gauge or should I put a reducer on the gauge even tho it seems to be working. I don't want the gauge to burn out or something like that due to too much 12 volt action.

 

I used the same unit Squirrel posted in my 51 Vicky. Still working after all these years.