Oil Pressure Gage and Sending Unit Revisited
Got around to investigating the high oil pressure readings on the factory gage of my '67 Barracuda.
Starting a new thread instead of sidetracking the original thread further...
I tested the gage operation using resistors and compared with the information from @RedFish and others. Summary: Using resistors clipped to the sending unit wire and body ground, the gage indicates properly.
Tested the sending unit by measuring the resistance with a digital multimeter with the engine running and comparing with the mechanical gage on the accsump. Summary. Sending unit resistance is very jumpy although it seems to average approximately correct.
Here's a video clip of it idling after warming up. Gage on accusump shows 40 psi.
My best guess is the sending unit should not be jumping around, and due to the difference in operation between the dash gage and an ohmeter, too much current is flowing through gage.
Does that make sense? Anyone have another possibility?
Here's a graph of the gage test with resistors (green squares)
The range of readings from the sender at 40 psi and around 60 psi are red and purple x.
Single 22 ohm resistor connected to sending wire.
Gage indicates center approximately 40 psi.
In contrast when the mechanical gage on the accusmp shows 40 psi
And the sender wire is connected, the dash gage shows around 70 - 75 psi.
Refer to the video above for the sender resistance at 40 psi.
Backstory here Rally dash redo
Got around to investigating the high oil pressure readings on the factory gage of my '67 Barracuda.
Starting a new thread instead of sidetracking the original thread further...
I tested the gage operation using resistors and compared with the information from @RedFish and others. Summary: Using resistors clipped to the sending unit wire and body ground, the gage indicates properly.
Tested the sending unit by measuring the resistance with a digital multimeter with the engine running and comparing with the mechanical gage on the accsump. Summary. Sending unit resistance is very jumpy although it seems to average approximately correct.
Here's a video clip of it idling after warming up. Gage on accusump shows 40 psi.
My best guess is the sending unit should not be jumping around, and due to the difference in operation between the dash gage and an ohmeter, too much current is flowing through gage.
Does that make sense? Anyone have another possibility?
Here's a graph of the gage test with resistors (green squares)
The range of readings from the sender at 40 psi and around 60 psi are red and purple x.
Single 22 ohm resistor connected to sending wire.
Gage indicates center approximately 40 psi.
In contrast when the mechanical gage on the accusmp shows 40 psi
And the sender wire is connected, the dash gage shows around 70 - 75 psi.
Refer to the video above for the sender resistance at 40 psi.
Backstory here Rally dash redo