engine temp guage issue

[Cwcb08]

my engine temp is not working

i took off the plug and grounded it and the guage goes all the way to hot, remove the ground the guage goes back, ok should be simple replace the sender. picked up a new one from car quest and installed ( no teflon just what was already on the threads ) replaced the bullet connector ( new sender has a smaller post ) fire up the car let run for 15 min, no reading, check the rad hose temp 165f, unplug the connector ground it guage moves.

im stumpped, guage works, wiring obviously works, and sender is new, any suggestions

[YellowRose]

engine temp gauge issue

Cody, is your gas gauge and other gauges working? Often, this can be a problem with the Constant Voltage Regulator (CVR) unit that takes the 12v from the system, and down grades it to 6v for the 6v gauges. This causes problems to the gauges, IF that 12V is getting to the gauges instead of 6v. But lets see what jopizz has to say when he sees this. I fixed your pix for you.

[Cwcb08]

the oil temp works, and im not sure about the ammeter, it sits in the middle even when the battery is disconnected, is that normal? the engine temp doesn't and the fuel guage didn't, i forgot to look at it again after i fixed the low fuel light relay

[YellowRose]

engine temp guage issue

As I recall, with the battery disconnected, or the key turned off, the gauges should go to the far left side and rest. At least that is the way it is on my Squarebird. Hopefully, jopizz or someone with better knowledge than me, will be on here shortly, and be able to help you. It could be anything, like a previous owner getting in there and wiring the gauges incorrectly.. Or a possible problem with that CVR unit. IF it is that, you may have to replace it. If you do, I would replace it with one of the new solid state ones. Our webmaster, Dave Dare ~ simplyconnected, can take your OEM CVR and convert it to a solid state one, and send it back to you. He can give you the details on that IF that is the problem..

[YellowRose]

engine temp gauge issue

BTW, Cody, all the wiring schematics for your Tbird are in the Technical Resource Library (TRL). You can click on them to expand them, or print them out as needed. If you do not have them, there they are for you. The link to it is always part of my signature element and also John's ~ jopizz.

[jopizz]

If the gauge goes all the way to Hot when you ground the wire your CVR is probably good. If you have a test light put it on the wire. You should see it pulsing and not solid. Did you ground the wire to the engine block or battery? If the sender is good and your engine is properly grounded it should work. If not it can only be one or the other.

John

[Cwcb08]

If the gauge goes all the way to Hot when you ground the wire your CVR is probably good. If you have a test light put it on the wire. You should see it pulsing and not solid. Did you ground the wire to the engine block or battery? If the sender is good and your engine is properly grounded it should work. If not it can only be one or the other.

John

i grounded it to the battery, i will test against the block 2moro as im about to leave for work

[Yadkin]

Fuel, oil and temp all work the same way. Each gauge is a little 6V heater that makes a bi-metal coil change length and at on the indicator needle.

The ammeter is different. For '64 it is an actual shunt, where full alternator amperage runs through it then over to the power panel on the passenger side kick panel. The needle should be in the middle with key off, to the left with key on accessories and stuff running, to the right with engine running. Later years (Dave Dare can verify) might use a remote shunt. These are a fire hazard if you install a higher amp alternator and power accessories, so plan accordingly.

For the temperature gauge, test the sender mounted on the intake, disconnect the wire. Use an ohmmeter between the brass hex and the electrical connection. It should read 100 ohms cold, 10 ohms when 180F. Then check ohms between the connector and the intake, then the block, then the chassis. If you don't have proper grounding the gauge won't work.

[Cwcb08]

If you don't have proper grounding the gauge won't work.

looking under the hood last night, where should the battery ground to the block? mine grounds to the AC idler pulley bracket?

[simplyconnected]

Where did Ford put it, or where does it belong?
Ford saved money by putting the shortest copper wire at the closest attachment point.

Your starter motor draws the most current so a good, healthy copper wire needs to stretch to that area. I run a #4AWG from the battery post to a bell housing bolt next to the starter motor. I also 'hang' both (starter motor and ground) wires from a clamp along the engine so vibration doesn't destroy the lug on the starter motor.

Notice that modern cars have a smaller (green #10) body ground wire, connected close to the battery. That's important to prevent body current from returning through drivetrain bearings. Ford cars used a braided wire that stretched from the back of the head to the firewall. - Dave

[Cwcb08]

Where did Ford put it, or where does it belong?

Yes where did ford put it on a AC car, mine is currently grounded to the adjustment bolt of the AC tensioner pulley bracket


Last night I Pulled off the wire to the sender to ground it to the block vs the battery and the gauge didn't move( when grounded to the block or battery ) electrical can be frustrating

[simplyconnected]

First, turn the key switch to the 'on' position. Then use your meter or a test light with one prod on neg. The other prod should be on the temp sensor wire and it should pulse 12 volts.

I prefer my homemade test light. It's simply a dash light soldered to two wires and taped. I have alligator clips on the ends of the long wires. I can see the light without looking at it and an incandescent lamp is a self-regulating load. If you don't have a spare dash bulb, use one of those holiday twinkle lights that cost three bucks per set. Cut off four or five bulbs in a series and lengthen the wires. Six bulbs in series will produce a slightly dimmer light but will last forever.

On a cold engine it doesn't matter whether the wire is on the block sending unit or not because the sending unit lowers resistance when the engine is hot (sending the gauge needle towards 'H').

Your fuel gauge works the exact same way; an empty tank has a high resistance to ground. A full tank sends the gauge needle to 'F'. Power removed (key off) should send the gauges to or below 'cold' or 'empty'. - Dave

[Cwcb08]

( it won't let me post when i answered within a quote )

First, turn the key switch to the 'on' position. Then use your meter or a test light with one prod on neg. The other prod should be on the temp sensor wire and it should pulse 12 volts.

I prefer my homemade test light. It's simply a dash light soldered to two wires and taped.

ok i will make up one of those lights

On a cold engine it doesn't matter whether the wire is on the block sending unit or not because the sending unit lowers resistance when the engine is hot (sending the gauge needle towards 'H').

like i posted, i tried this on a cold engine and it didn't move when i grounded it but i dont know why, it worked last test?

Your fuel gauge works the exact same way; an empty tank has a high resistance to ground. A full tank sends the gauge needle to 'F'. Power removed (key off) should send the gauges to or below 'cold' or 'empty'. - Dave

when testing the low fuel light the one wire i grounded made the light come on, if i ground the other the guage should go to full? i tried my multi meter on the sender and the number kept jumping up and down i guess it was the tank sloshing as i had backed her up onto ramps a few minuets prior( does that sound like a bad sender?)

[simplyconnected]

You can do all your electrical tests just using the wires connected to (both) the sending units.

Disregard the Low Fuel Relay. You need to look at power that starts at the CVR (constant voltage regulator). The CVR feeds both fuel and temp gauges with the same power, which is pulsating 12-vdc. In fact, the gauges are identical, too.

You are looking for the gauges to deflect to full scale, here. Each gauge feeds respective sending units that both run between 10-100 ohms. Ten is 'hot' or 'full' and 100 is 'cold' or 'empty'.

Grounding either wire at the sending unit should send the gauge to full scale. Limit this time to one minute (or use a 10-ohm resistor in series). If you don't see power at the sending unit move to the gauge. If you don't see power at the gauge, you need a new CVR. It's that simple.

These gauges and sending units are made by King-Seeley for Ford. They use current through a ni-chrome wire wrapped around a bi-metal strip to move the needle. That means the polarity on the gauges makes no difference. There is no motor or armature, only a bi-metal strip that bends with heat. That's why we rarely see 'bad gauges'. CVRs go bad all the time. When new, they have a on-off duty cycle of 50%. As they age they get erratic, they open or they short inside.

BTW, I convert CVRs to solid state. - Dave

[Yadkin]

looking under the hood last night, where should the battery ground to the block? mine grounds to the AC idler pulley bracket?

This is the most important ground on the car- it shouldn't be on a bracket, but directly to the block. Mine's on the passenger side in front. The bolt is fairly large, screws in horizontally into the side of the block. See the copper in the picture? That's the connector.

Don't get confused by my custom serpentine belt assembly or headers.