Who knows about a relay for oil & gas tank gauges?

[KBMWRS]

'67
Ever since Craig and I installed a oil gauge (original type which Craig checked out and worked) where the clock use to be it never really gave a reading. It would move a little but not give a real reading.

I have since learned that the oil sensor is not getting enough voltage and that there is a relay under the dash which has one other sensor connected to it...the fuel. Of course getting a new relay would mean the gas gauge probably would not read correct and the float would have to be adjusted.

So...where is this relay under the dash? And what does it look like?

M

 

[Midlife]

It isn't a relay; it is a constant voltage regulator. It takes the 12V from the ACC line, and cuts it down to about 5-6V. It supplies power to the gauge, then out to the sending unit, where the electrons find their home (ground). The CVR is about 3/4" x 1.5" by 3.4".

To test whether the gauge is good or bad, you can swap the oil line to the fuel gauge and vice versa. If the new gauge reads like the old one, then there is a problem in the wiring past the gauge. If the gauge (oil) stays low, then the gauge or the wiring to it is suspect.

 

[JeffTepper]

Mike, is that the CVR I gave you several years ago? Following up on Randy's post, if your temp and gas gauge are working then your issue could be the sending unit on the oil filter housing or the gauge itself. To test the gauge, temporarily run a jumper from the sender wire to ground and briefly turn on the ignition while watching the gauge needle. If the needle moves across its sweep, the gauge is likely good. Do not leave the key on too long.

 

[tarafied1]

I have a 68 oil pressure gauge installed in my 67 where the clock was and it works properly. I just used the wires that went to the original oil pressure gauge. It was removed to install a tach where the original oil/amp combo gauge was.

 

[Midlife]

One other thing to consider: is that the right oil pressure sending unit for gauges? Or is it for later years or for an indicator lamp? Later years had a much different resistance range.

 

[crustycurmudgeon]

What Mid said. If you changed from the idiot light to the gauge you need to change the sending unit.

 

[KBMWRS]

I have the correct sending unit on the oil filter housing. The gauge itself was checked before install by Craig. The system WAS tested and the oil gauge is not getting enough voltage.

I just need to replace the CVR as Randy has stated...Now to find it.

And then I'll need to re-adjust the fuel sending unit for no doubt when it gets the proper voltage it will read incorrect.

 

[Midlife]

Before doing that, I'd check the continuity from the oil sending unit connector through to the gauge connector. Your wiring may be faulty with just a high resistance contact somewhere between those two points. I've seen many 90* connectors increase resistance up to 22 ohms or so simply by the internal crimp loosening on the wires. A sharp tug on the wire before it enters the molded connector sometimes corrects this problem. A higher resistance in the circuit means a lower reading on the gauge.

 

[6t6red]

Before doing that, I'd check the continuity from the oil sending unit connector through to the gauge connector. Your wiring may be faulty with just a high resistance contact somewhere between those two points. I've seen many 90* connectors increase resistance up to 22 ohms or so simply by the internal crimp loosening on the wires. A sharp tug on the wire before it enters the molded connector sometimes corrects this problem. A higher resistance in the circuit means a lower reading on the gauge.

Hmmmm. I will have to try that with mine also. Thanks Mid.

 

[KBMWRS]

And everyone goes....Hmmmmmm

 

[crustycurmudgeon]

I recall I had a low reading oil pressure gauge. I replaced the sender (I had the correct one already) and cleaned the connector and it reads normal now. I don't know which of those two things actually corrected the problem.

 

[KBMWRS]

I have the correct sending unit on the oil filter housing.

 

[crustycurmudgeon]

I was implying that maybe the sender you have is bad, despite being correct.

 

[KBMWRS]

The oil sensor was checked. That is how we found out it wasn't getting enough voltage.

 

[Grabber70Mach]

But doesn't the oil sender just basically supply a varying resistance to ground?

 

[tarafied1]

the gauge cluster doesn't use constant voltage, there is a regulator that pulses the voltage. I didn't know about a relay...

 

[Grabber70Mach]

Craig that is my understanding also. I'm pretty sure most digital multimeters won't show that pulsating voltage. I think the older Simpson VOM'S that had a movement will.

 

[tarafied1]

I just need to replace the CVR as Randy has stated...Now to find it.

See that rectangular looking thing on the right just above where the speedo cable attaches and below the wiper switch plug? That's it. It's held onto the gauge cluster by a screw.

 

[KBMWRS]

Thanks Craig I'll know what to look for now. I'll try Randy's solution first......
I think I'll wait until after Knotts...this way at least I'll have a gas gauge.

 

[tarafied1]

good luck and enjoy Knotts!