Temp gauge reads high. 1959 Ford Galaxy 332 V8

[Snee Oosh 59]

With all new or tested parts involved (voltage adjuster, fuel gauge, temp gauge, temp sensor) and the tests all completed per a factory manual, the temp gauge reads off scale high as soon as the key is turned on. It slowly goes to high scale, not fast like a grounded wire. All tests indicate either a bad gauge or a grounded wire to the sensor, but the gauge tests OK and replacing the wire results in the same high reading. The temp sensor has been replaced and shows ohm reduction with temp rise, but evidently not enough ohms when cold to keep the gauge down. Assuming the above, is the only remedy to install resistor/s in the line to the gauge from the sensor?

[Snee Oosh 59]

Maybe I should have included that the new temp sensor is an Echlin TS6464 which is the correct one according to NAPA.

[Bloo]

Is the fuel gauge accurate?

 

What happens if you disconnect the wire at the temp sensor?

 

The little flasher can thingie affects both gauges. If one gauge is OK, it is probably OK. I believe the little can should be "on" about 50% of the time. If the fuel gauge is accurate, we can probably rule out the little can.

 

Gauges are thermal so always rise slowly. It does sound like a shorted wire, but if you have tried another wire I guess not. If the temp gauge goes all the way down when you disconnect the wire, It is probably fine.

 

I have the ohms measurements in a book somewhere but I can't get to it. I just found in an old forum posting that a Ford sender (with this type of system) is 75 ohms cold and 10 ohms hot. I can't verify. I believe you could check sending unit ohms at room temp (cold engine) on any other 60s or early 70s Ford you might have available that has a factory temp gauge (not a light) and it should be very close to the same. It wont be exact though. The tolerance is a bit loose. Measure from the sending unit post to the block with the wire disconnected.

 

Best guess is the new temp sensor is bad, but I would measure it at room temp and compare to another Ford. If they are close to each other, then the gauge itself is probably bad. Before condemning the gauge, make sure it is getting it's 50%-ish interrupted power from the little can like the gas gauge does. If the temp gauge is running on pure 12 volts, that could cause your trouble.

 

I doubt you would get any satisfaction by adding resistors. You could bring down the gauge that way for sure, but the amount of swing per degree could easily be way off. It's hard to predict. It might be OK and it might be a mess. Better to find the actual problem.

 

One last thought: Are the engine and body grounded together?

 

Welcome to the forum!

 

 

Edited April 9, 2023 by Bloo (see edit history)

[rocketraider]

A while back m-mman posted this fantastic Ford Rotunda factory tool that tests and troubleshoots wonky Ford gages. Now, he probably has the only working one left in existence, but might be something to keep an eye out for.

 

[Snee Oosh 59]

Thanks for the quick reply.

The fuel gauge is accurate.

If you disconnect the wire at the temp sensor the gauge stays at C.

The voltage adjuster is new and tests to show it varies the voltage as shown in the factory repair manual.

The gauge rises slowly normally, but is instantaneous if the wire is grounded.

Old temp sensor reads 430 ohms at 55 degrees, and new one 320. Don't have hot readings.

Hard to find a 50's 60's car  here.

Engine and body are grounded.

The original factory repair manual is great and gives all the troubleshooting and explanations of the functioning theory.  I have followed all of the instructions they give and am left wondering if there wasn't a different temp sensor with higher ohm readings available in 1959 that I can't find now?

Thanks!

 

[Bloo]

Maybe there's a different sensor but I doubt it. This is pointing strongly to a problem with the gauge itself.

[Snee Oosh 59]

the factory repair manual says to test the gauge with 2 flashlight batteries, the 3 volts should  read approximately H (fullscale) it does. Not sure how else to test it.

[Bloo]

I'm flying by the seat of my pants now because I can't find this in a book. It is looking like there may have been a change around 1963-65, and also the old 6v stuff apparently swung the gauge backward so no help there.

 

On 4/8/2023 at 5:07 PM, Snee Oosh 59 said:

Maybe I should have included that the new temp sensor is an Echlin TS6464 which is the correct one according to NAPA.

Echlin ts6464 looks likely correct. Napa's info is terrible, but it looks like it fits a bunch of late 50s Fords and AMCs so there's a real good chance it is electrically right. 13.5 ohms at 220F allegedly with 9% tolerance. They tried to specify at 100F too, but they dropped the ball.

 

I scraped from a forum (and can't prove) the following. It's mid or late 60s info, so may not be the same? Anyway, 10 ohms = hot, 23 ohms = half, 73 ohms = cold on the gauge. It looks like that would put 220F up at almost the top of the gauge, so that's believeable. Unfortunately NAPA didn't give enough info to figure out what would be happening at the other end of the gauge. These numbers do look promising.

 

3 hours ago, Snee Oosh 59 said:

the factory repair manual says to test the gauge with 2 flashlight batteries, the 3 volts should  read approximately H (fullscale) it does. Not sure how else to test it.

That doesn't sound right at all. Did the factory shop manual really say that? I would have expected something more like half scale. Any chance they could they have said half scale?

 

The way I remember, the little flasher can runs at a 50% duty cycle. Hmm.. Maybe that's wrong. But, if we assume a 50% duty cycle (switched ON half of the time), that works out to about 7 volts RMS on a charging system running at 14 volts. 7 volts RMS produces equal heat to 7 volts DC, and these are thermal gauges. There's 7 whole RMS volts to run the gauge, and that would really peg it if the sender wire was grounded. It's true they do peg when you test them, but the difference between 3 volts and 7 volts (4 volts!) would be dropped in the sender. It's more than the gauge is running on, at least when the temp reaches the high mark, and would drop even more at low temperatures.

 

I don't quite buy it, and I still suspect the gauge.

 

P.S. If you can't get a hot ohms reading in the car, maybe boil one of those senders on the stove? 212F isn't quite 220F, but it might give you a good idea if the sender is way off.

 

P.P.S. Just in case you don't already know, when measuring low ohms like 10 ohms (which you might see), zero your meter. If it's digital, the function is called "delta". Short the leads together and hit the delta button. Alternatively, if you don't have delta, short the leads together and write the number down. It's the resistance of your test leads. Then, when you measure ohms, subtract that number from the reading you took.

 

Edited April 10, 2023 by Bloo (see edit history)

[Snee Oosh 59]

Attached is a picture of the original ford factory manual in regard to the gauge test.

The manual says that the voltage reduction device will average 6 volts. It is new and tests to show it varies the voltage as shown in the factory repair manual.

I'm still stuck.

I appreciate the help though.

 

[Bloo]

Can we see the next page?

 

[m-mman]

This is the important information from my tool 

 

You need to read it carefully but it says that for the TEMP gauge needs 73 ohms to sit a low. (middle is not given) and 10 ohms to be at high. 

 

You can connect the ohm meter to the sender under the hood. one wire to the connection one wire to ground. Check it cold them warm up the motor and check it. 

Confirm water temperature with an actual thermometer. Maybe, just maybe, it really is that hot?

 

Forget the battery thing.  Get your test light. Connect to the wire coming from the firewall to the temp sender. With the key on it should flash just like a turn signal. Get your ANALOG volt meter. Connect it to the wire and the needle should bounce back and forth between 12 volts and almost zero volts but AVERAGING 6-8 volts. The Constant Voltage Regulator is a simple thing. 

 

You said that you "replaced the wire".  Uhhh. . . tell us more.

Did you REALLY open up the harness and run a new wire through the firewall? Did you connect a TEST wire under the dash and run it out the door and to the under hood sender?  Each of these things could affect the overall resistance and therefore the gauge. 

 

Are you sure that the wires on the back of the gauge are plugged into the correct side of the gauge?

One side is for "power" the other side goes to the sender. 

Edited April 11, 2023 by m-mman (see edit history)

[Snee Oosh 59]

Thanks for all the info .

 

I connected a 12 gauge wire to the gauge and ran it out the door and connected it to the temp sender. It would have been a little longer than the original, but not sure it would make very much more resistance.

 

The wires are plugged into the same sides they have been since I got the car, but I cannot for sure say they are correct. I'll see if I can find an accurate description of which side is which. I do know that the red/white wire going to the sending unit is on the passenger side of the gauge.

 

Thanks again