1965 wiring issues

[SLICKCOLLECTOR]

I am about to finish an 8 week thrashing on a project. the truck is a 65 shorbed with 460 and c6 combination. I decided to opt for a custom cab dash insert with the auxiliary gauges this time instead of buy aftermarket mechanical oil and water temp gauges. I also am running blue strain relief Duraspark ignition. I have the truck running and starting fine now and have no mechanical issues as the motor was ran in on a run stand prior to install. my wiring issues are as such: my factory water temperature gauge is working but reads barely above bottom peg when it is running against the thermostat at 180 or 190. it does move off the bottom when I turn the key on. however it does not move to the middle of the range as it should. if I ground the gauge with a tester it does move up towards hot. my test lite shows a faint glow when I ground the stud on the sensor with the motor running.. when I tested the temp wire it had the pulsating lite as indicated from my searching. is the sensor supposed to have Teflon tape on the threads going to the intake manifold. by doing so does that interfere with the ground. does it need to be grounded? my auxiliary amp gauge works. I can't believe it! but my auxiliary oil pressure gauge does not work. my oil pressure idiot lite works as well as my alternator idiot lite. my fuel gauge works. turn signals, emergency lites, headlites, tail lites, etc all work. how does that auxiliary oil pressure gauge work. I get no current flowing thru the wire to the sending unit. is that correct? I am wondering whether I have the right sending units for the temp gauge and oil pressure sending unit. I have searched the site and read about all their is said about the subjects. thanks.

[Roger Carter]

The sending units are different for gauges than for the idiot lights. You have to have the correct sending units. if you want to run both gauges and lights you will need two separate sending units, and wiring.
Ford had an "overlay" harness for gauge wiring when the CC sweep speedometer cluster was use. This included under hood and under dash wiring.

The sending units need to have a good ground to the engine for the gauges to work correctly. I have seen Teflon tape act as an insulator and cause problems as you describe. I prefer to use an electrically conductive sealer rather than Teflon take in these instances.
The basic instrument circuit (oil, temp, fuel) powers the gauge hot through the IVR. The wire to the sending unit is the gauge "ground" wire and the sending unit is a variable resistance, or "dimmer". The IVR pulses, effectively lowering the voltage to the gauges. The gauges "see" about 5-6 volts. When you ground d the wire to the sending unit you have completed the circuit for the gauge and removed most all the resistance in the circuit. That causes the gauge to read "full", "hot" or "high".

The factory temp gauges that I have seen typically run at 1/4 gauge or less with a 180* stat. They aren't known for accuracy.

Hope this helps.

[SLICKCOLLECTOR]

The sending units are different for gauges than for the idiot lights. You have to have the correct sending units. if you want to run both gauges and lights you will need two separate sending units, and wiring.<br abp="237">Ford had an "overlay" harness for gauge wiring when the CC sweep speedometer cluster was use. This included under hood and under dash wiring. <br abp="238"><br abp="239">The sending units need to have a good ground to the engine for the gauges to work correctly. I have seen Teflon tape act as an insulator and cause problems as you describe. I prefer to use an electrically conductive sealer rather than Teflon take in these instances.<br abp="240">The basic instrument circuit (oil, temp, fuel) powers the gauge hot through the IVR. The wire to the sending unit is the gauge "ground" wire and the sending unit is a variable resistance, or "dimmer". The IVR pulses, effectively lowering the voltage to the gauges. The gauges "see" about 5-6 volts. When you ground d the wire to the sending unit you have completed the circuit for the gauge and removed most all the resistance in the circuit. That causes the gauge to read "full", "hot" or "high".<br abp="241"><br abp="242">The factory temp gauges that I have seen typically run at 1/4 gauge or less with a 180* stat. They aren't known for accuracy.<br abp="243"><br abp="244">Hope this helps.

I have 2 different oil sending units. one small and one large. the idiot lite works and uses the small sending unit. the large sending unit is for the gauge. I have the auxiliary harness and I think I have it wired correctly. the amp gauge from the other side of the dash works.. I will remove the Teflon tape from the temp gauge and see if that helps create a better temp reading. the auxiliary oil pressure gauge does not move at all and I think I have it wired correctly. does it use the ivr whizzo voltage as well?

jim

[ThinLizzy13]

Dunno if this helps but isn't there something with the stator being hooked to the voltage regulator for idiot lights vs not hooked up for gauges?

[tomrooster]

The aux oil press gauge gets the power from the same IVR but there is a double wire connector that needs to get hooked up. It is with the with the wires for the amp gauge , I had a little trouble figuring it out but Brian ( Ice Man ) helped . Tom

[SLICKCOLLECTOR]

The aux oil press gauge gets the power from the same IVR but there is a double wire connector that needs to get hooked up. It is with the with the wires for the amp gauge , I had a little trouble figuring it out but Brian ( Ice Man ) helped . Tom

I remember seeing a pigtail attached at that end of the harness. i'll dig out another harness and see if I can follow what you are saying. I thought that wire might be a dash lite extention. I don't have any parts trucks that still have wiring harness intact. they have all been disassembled and I don't see them complete parts trucks for sale anymore. at least none that are reasonably priced. thanks for the tip.

jim

[SLICKCOLLECTOR]

i have no signal at the sending unit. white/red wire. oil auxiliary gauge has a white/red wire with a pulsating signal. black/green wire with a pulsating signal. the other 2 wires on the gauge go to dash lite for gauge and the lite works. question is does the white/red wire at the sending unit require an electrical signal that pulsates to work? is the IVR an electrical whizzo that creates that pulsating signal to power most of the gauges?" DC TO AC CURRENT. thanks.

jim oberg

[tomrooster]

The IVR supplies the power to gas, oil , temp guage, it goes on one side of the gauge the sensor goes to the other side, red/white - oil gauge. On the normal wiring harness there is no provision for the oil gauge so the wire ( I think black / green ) with the double connector goes on the IVR and the other part goes on the gauge then the other gauges can connect to the other side of the double connector on the IVR. I would take a picture but the truck is put away in a container so I have room to work on the other parts of the truck. Tom

[SLICKCOLLECTOR]

I have seen the pictures of the splitter for the IVR connection that ICE posted. I am showing that pulsating signal on one side of the gauge. no signal at the sending unit. the auxiliary gauge wiring harness I used was intact with no obvious flaws and all wires are accounted for. I am starting to wonder if the gauge itself is bad. I am not an electrician and don't understand how it all works. is there supposed to be a + current at the wire at the sending unit? I am starting to think the gauge itself is bad or the sending unit. thanks.

[tomrooster]

Why don't you hook the 2 wires together at the gauge then test for current at the sending unit , That will tell you if the red and white wire is good or disconnect the red and white wire from the gauge and test the terminal that you took the wire from or just ground the terminal with a jumper wire and look at gauge , it should move. Tom

[SLICKCOLLECTOR]

the 2 wires together at the gauge provide no current at the sending unit. with wires attached to be back of the gauge I show the intermittent current at both poles. the white / red wire shows no current when the wires are disconnected from the back of the gauge. the black/green wire has a signal . the gauge does not move if I ground the terminal. the way I have the gauge wired is the black/green wire is on the driver's side of the gauge. the white/red wire is on the passenger side of the gauge. the sob shows me no love. I get no signal at the sending unit ever.

jim

[unibody madness]

Sounds like you may have a broken wire or a dirty connector in line. I used the white with red stripe wire with the small sending unit, drilled a hole and installed the idiot light into the back of my oil gauge that runs with a separate wire to the large sending unit, through the regulator.
They both work when they are supposed to.
If you got rid of the teflon tape, and still have a problem, I bet its a dirty connector or broken wire.

[tomrooster]

Like uni says sounds like bad wire, or connector, on my truck I had the black/green on the passenger side, not sure if it makes a difference. When you grounded the gauge did you ground one terminal while the black/green was connected on the other ?

[SLICKCOLLECTOR]

Like uni says sounds like bad wire, or connector, on my truck I had the black/green on the passenger side, not sure if it makes a difference. When you grounded the gauge did you ground one terminal while the black/green was connected on the other ?

I will try it again. I don't understand how the gauge works and the flow of electricity from point to point. it is magic to me. maybe that is the problem. i'll try reversing the wires. i guess i can't screw it up as it doesn't work now. thanks.

jim

[tomrooster]

Well if you ground one side of the gauge and have power on the other the gauge should move. If it don't gauge is bad. Make sure you have a good ground with a test light or something. If you want send me a PM and I'll send my phone # and talk you thru it. Tom

[SLICKCOLLECTOR]

65 texas truck 006.JPG

65 texas truck 003.JPG

I got to do my first burn out yesterday.

jim

[dirtbike]

Silly question of the day

what is IVR?

I recently changed over dash cluster and the fuel and temperature go straight to max. I tried fitting the old one again which used to work perfectly but it is now doing the same. I did not change anything else. Any suggestions on why it would do it now after changing over cluster?

[unibody madness]

There is a voltage regulator at the bottom of the cluster.
Black and green wire should feed through both gauges, to sending unit ground, in order for them to work correctly.
Black and green comes from dash wire loom to rectangular ivr.
Split wire black and green wire harness should go from constant voltage regulator one to each gauge
Red white for temp
orange for fuel sending unit

[dirtbike]

Problem solved, bad earth on voltage regulator.