oil sending unit, is it bad?

[davek]

70-440 I have a mechanical gauge that I installed that says 75psi running and 30 at idle and my gauge on the dash would stay pegged,been this way since I bought the car. so I bought a new oil sending unit and now it says 35psi driving and 15 at idle. I think the new one is bad. What do you think? thanks Dave

 

[Ranger16]

I don't know if it's "bad", or maybe just cheaply made, but it sure is WAY off.

 

[dadsbee]

Somewhere in my resto thread I covered resistances at different pressures on the sender, as I had a bad one when I started the Bee for the first time after it was back together.. I'll try to find some time to find it. Oil pressure is the same as Fuel level... Full gauge is ~10ohms, zero is ~70ohms.

 

[davek]

Somewhere in my resto thread I covered resistances at different pressures on the sender, as I had a bad one when I started the Bee for the first time after it was back together.. I'll try to find some time to find it. Oil pressure is the same as Fuel level... Full gauge is ~10ohms, zero is ~70ohms.

would that cause my fuel gauge to bounce around if the resister is going bad on the back of the gauges?

 

[dadsbee]

There is no resistor on the back of the gauges! The resistance comes from the rheostat in the fuel sender, same as the oil pressure sender and thermistor in the temperature sender. Loose gauge connect to the circuit board or more likely a loose sender connection or ground clip. Let me look for the sender values, I believe they're in my resto thread on this forum..

 

[Jerry Hall]

would that cause my fuel gauge to bounce around if the resister is going bad on the back of the gauges?

It's probably the internal resistance of the sending unit. What is your mechanical gauge doing at the same time?

 

[dadsbee]

Here yah go.. https://www.forbbodiesonly.com/mopa...oupe-restoration.145777/page-6#post-910903356

40 psi = 31 ohms

60psi = 26 ohms

80 psi = 19 ohms

 

[Jerry Hall]

Here yah go.. https://www.forbbodiesonly.com/mopa...oupe-restoration.145777/page-6#post-910903356

40 psi = 31 ohms

60psi = 26 ohms

80 psi = 19 ohms

Great information!! Thanks

 

[davek]

There is no resistor on the back of the gauges! The resistance comes from the rheostat in the fuel sender, same as the oil pressure sender and thermistor in the temperature sender. Loose gauge connect to the circuit board or more likely a loose sender connection or ground clip. Let me look for the sender values, I believe they're in my resto thread on this forum..

I was thinking of the limiter

 

[davek]

It's probably the internal resistance of the sending unit. What is your mechanical gauge doing at the same time?

mechanical gauge works fine its just the dash gauge is way off.

 

[dadsbee]

It either makes a 5 volt pulse or it doesn't. If it sticks and goes 12volts it fries your gauges.

 

[davek]

It either makes a 5 volt pulse or it doesn't. If it sticks and goes 12volts it fries your gauges.

limiter is good